Transcript for:
Earthquake and Map Reading Overview

hi everyone and welcome back I hope you had a good weekend so this week we're going to continue with earthquakes and then we're going to move on to like cartography which is basically map making specifically we're going to be talking about how to read and understand a topographic map which is a very important skill and feature you know in all of the earth Sciences or geography or things like that so um so this is going to be a short lecture uh compared atively that'll be about 2 hours long and that's to account for the 1-hour test that is also going to happen this week so we're going to begin this lecture uh with you know a brief uh discussion on some earthquake hazards and then we're going to go on to some basic information to understanding um topographic maps and then from there we're going to you know be done with the lecture part I recommend you do the lab after this because the lab will be applying how to do this topographic information how to calculate slope things like that this will be good information for you guys to have for the test of this week so I would do the test last the test is going to be 50 questions long and it's set to be like an hour um but I'll probably give you guys a few extra minutes in that you know just in case as a reminder the test will be open book and open note but make sure you study ahead of time because if you have to look up everything there is no way you can possibly finish in time and as you're preparing to take the test take a chance to look through the study guide I posted to uh look through the or do the practice test I gave you know get some practice in with how these questions might look you know that would be a good opportunity to get a little bit of work done in that regard to get a feel for how the test is going to be like before you start it um and also as a reminder there will be a standard extra credit option that's on this in every test and that is uh there will be an option it will be on the module after the test t for you to upload your study guide that you created yourself for some extra credit points and then there will be another option it'll be a small little questionnaire thing that will help me out and you'll get some extra credit points for that now the way the extra credit will work in this case is some number of days after the test is finished and I have all the grades in and everything like that I will go through those extra credit calculate up the points and then I will add those points directly to the test so there'll be marked in canvas as worth zero points but that is because I will be adding the points directed to the test so I do it that way so the points don't get added twice now if you have any questions about this please email me and if you need any special accommodations for the test whatsoever it is very important that you email me right away and definitely before you take the test so with that why don't we get started now I went over all of this data uh in the first lecture you know the uh we're talking about the play boundaries but I wanted to put it here again just for your personal reference because you're going to need to know this you know divergent boundaries are associated with tension stress and they usually can create normal faults and usually add a divergent boundary you get these Associated strikes up faults the strikes up Faults Are sheer but but the tension creates the normal faults a convergent boundary creates compressional stress and they create either reverse vaults or thrust faults which is only you know differ in their angle and then a transform boundary is going to create sheer stress and that is going to generate strikes their faults so again this is very very important Point that's why I put it here for your review and it's always good to kind of think of how these things relate you know because as you're going through this don't look at all this data in isolation try to make connections with what you're learning now with what you learned in the past because by doing so you're going to have a much higher understanding and a much much much higher retention and this has been proven repeatedly in pedagogical studies actually just consider not just for your own studies but also think about that you know when you're teaching you guys may have noticed that as I've been going over this material I keep referencing back to stuff we've already talked or I've already talked about and I also reference things that are going to happen in the future because I'm trying to make as many connections as possible to help increase you know that retention okay so let's go into uh you know different types of earthquake damage so the first type is going to be something called liquifaction and liquifaction is basically cuse when seismic waves liquefy waterfill sediment now I don't want to go into this into too much detail uh we're going to talk about this a little bit more you know later on um when we talk about pore pressures and things like with hydrology but you can imagine that dirt is basically almost like a bunch of like very very little rocks and the siment is ultimately that it's usually very very little rocks or like pieces of rock you know and and they could be small they could be microscopically small but they're effectively a bunch of little rocks you can imagine that this bunch of little rocks are just sort of all kind of piled on top of each other and you might have of course some life and stuff there like roots and whatnot but but just imagine this giant pile of rocks now that rock those rocks are going to have some water between it when they're in the ground if it's near the surface like here in Fresno you're going to have relatively little or none you know especially in the height of Summer but you're going to usually have some um as you get deeper of course or you know in areas that have that's not quite as dry as Fresno um you're going to have more rock there now that siment the reason why when you step on the ground you don't just start sinking even though it's just a pile of loose rocks you know held together by gravity um is because of friction or or held in place by gravity is because of friction you know similarly how you walk you know you don't just have your feet step out underneath you there's friction between your foot and the ground underneath you while every one of those little pieces of The Rock has friction with every other little piece of rock so they just are kind of held in place you know if it's like loose sand at the beach you have less friction which is why when you're walking on the beach you know some of it of course kind of slides and you know steps away when you make those footsteps but you don't just keep seeking add INF an item because you know eventually the friction adds up enough to stop your weight but some if you have the seismic waves you know like an earthquake what sometimes happens is you're causing all of this shaking of these Rock pieces and as you're causing all of this shaking of these Rock pieces you can you're actually also shaking the water and the water that's between there can actually start to lubricate all of those Rock pieces and and as all of those Rock pieces are being lubricated well you're you're reducing the friction between it so their ability to resist motion when they rub against each other is less it's sort of like you know having it you know like you're walking of a bunch of friction and then suddenly I throw a bunch of oil on your Sho the bottom of your foot you know it's like well your shoe had like a bunch of friction but now that it's covered in oil there's less friction you're going to slip that's the whole principle behind liquefaction that the water is basically pushed to kind of lubricate all those sediments so suddenly there's a much less friction on top of that during the act of the earthquake the frictional coefficient becomes very low because of the shaking itself now this we call it liquefied sediment and it's still a solid it's just like a like a soggy solid you know like um like a frappuccino you know um and like like a slush you know I mean slush is a bunch of ice but it's a bunch of ice that's very loosely held together that's a good way to think about it actually is it's like a slush um and so when it's in this liquefied state it can flow and actually this does this can create mud flows on like slopes you know mud flows is one of the types of mass wasting but let's say it happens just on some flat ground if the sediment is sand this creates quick sand and I'm sure everyone heard of quicksand and though quicksand is not nearly so deadly as you know TV shows and movies like to have us believe it is still actually a problem and it still could be very dangerous um for example in the old west days when cattle ranchers were having to move their cattle across the country one of their big fears was actually crossing rivers because it is not uncommon to have it's not common completely but it's not also completely uncommon to find quicksand at the bottom of certain Rivers so the cattle you know the quick sound may not be too strong but the cattle when they cross being heavy suddenly start to sink and of course I'm not saying that's going to suck them down you know endlessly like they show in these movies but it could have them sink down far enough where their heads below water uh and if that happens they drown and once they start to sink in it can become very hard to pull out so I have a kind of a related story and I mean it's a little bit different but um but the the effect is the same and I used to do archaeological surveys in farm fields in the Midwest and this farm field is basically tilled soil so it's it's sediment that's like a lot looser in the ground you know and in Illinois you can get a lot of rain and so when you get a lot of rain this loose sediment especially right after it's been tilled can and especially if it has like a lot of silts in it becomes like a sloggy muddy mess and so you know as we're traing through this we call these like you know 20 lb feet because you step in and your feet sinks down like a good foot into the mud so in a sense it's kind of like quicksand a little bit there I mean but not quite but it's it's a very similar concept you know because it has been slightly liquefied and you know of course you can pull the foot out you know but because your foot got you know pushed in the uh the mudle bit you get like a suction effect so you it's really hard to pull your feet out you know you have to kind of yank your foot out every step and of course just to make things more difficult as you're yanking your foot out assuming your shoe doesn't stay behind you just yank your foot out of your shoe which has happened to me a few times um assuming you get your shoe out with it you're also bringing with it like 20 pounds of mud you know so your next step your feet are literally 20 lounds heavier so in a sense you're walking with 40 extra pounds of weight and you're happy to like with all your Force yank your foot out which means that you know you could walk you know 5 6 700t 1,000 ft to get to the site and and it takes forever and you are exhausted by the time you get there so those aren't Pleasant days but and the effect is the same now with quicksand you know you could sink in like a foot like in that river that foot could be enough to drown a cow for example or a person um or it could be you know many feet and if and if it's like movies for example it could be enough feet that you know you actually you know drown but usually the fear is that you step into it and then you you just can't get out you know one way or the other now we call it quick sand because you know if the main sediment sand if it's if Clay is the main sediment we call it quick clay but I will admit I have seen many many people in common components call all of it quick sand but if it's Clay it's quick clay now another major effect of this is that you know land that is unstable meaning you don't have a lot of pedogenesis and um biogenesis that's holding it together you know during this process the pieces of that land can actually crack and form into small blocks you know imagine like taking a brick and hitting it with a hammer you know you're going to break it into pieces the ground can do this same because especially if you have a lot of clay because it forms these tabular pedogenic structures that will hold pieces together but you know the shaking can break it you know kind of like hitting with a hammer it can break one piece from the other but it will still retain its General Integrity because of the pedogenic tabular structures don't worry about the term pedogenic it's just a term meaning basically altered by soil processes uh so the picture on the top here is going to be a picture of some of that foundering person for scale and the bottom picture kind of shows um you know what could happen there now one of the interesting things that can happen when you have this foundering you know this cracking of the soil is you can create sand volcanoes because let's say you have a layer of sediment that's mostly silt in muds so you have that like you know ability to founder and crack it could just Happ in sand too but you know it's a little bit easier in some some finer you know materials and then you have like um like a nice thick layer of sand underneath it you know and keep in mind that there's still water through this thing it's one of the things we're going to talk about but you got water in the ground um then when the thing when you start to uh found or whatnot you know sometimes you know you might have those full big cracks but sometimes you'll just create like a little crack and as that little crack forms well all of a sudden you have an because the water and and the sand in that water is under pressure from the ground above it and so when you uh release a put a crack to the surface then suddenly that water has somewhere to go so imagine like having a Capri Sun and you're kind of holding it just a little tight you know it's under a little bit of pressure and that little bit of tightness that that squeezing you're doing will be the equivalent of like the weight of all the ground above you and then you take your straw and you poke a hole in it and when you poke a hole in it that's kind of like the founder you're making a crack in that that layer that ground above it that's sealing it in and now you got a direct Outlet to the low pressure air and you're squeezing that capr sun all of a sudden the capr Sun juice is going to be spouting out that's that's effectively the same principle and we call them sand volcanoes because you know as that water is rushing out you know it's it's brings the sand in the lower layer that loose sand along for the ride so so it's kind of just spitting out sand and we call it a volcano because the process is effectively the same as what a real volcano does it's just that instead of it being you know liquid rock you know it's going to be watery sand you know but it creates like volcano like structures although they're never going to be big I mean not like a real volcano so with this liquefaction you know in the foundering you can have you know surficial sliding so you can have a bunch of faults that were effectively deactivated but you know the liquifaction I talked about this earlier you know uh that those vibrations that shaking can cause like you know the lubrication of the Fall plane and the shaking can actually break the frictional barrier and you can have the land actually topple and so you can actually have it you know going from being upright to kind of coming at an angle and you can see it in the picture pretty well and the picture on the top which I believe comes from Hong Kong but don't quote me on that um actually shows like some of these solid buildings you know like the ground started to shift but you know being solid they you know they just toppled so this is actually a potential major um problem and there are places on the world where this causes billions of dollar billions of dollars of damage after a major earthquake especially if this were to happen in places like Hong Kong for example that is super or New York City which it wouldn't happen in New York City but in places like that that are really built up with really expensive real estate it could become very costly I talked about the sand volcanoes uh I just want to showcase uh some cooler pictures of this so you can kind of see like uh let me do this in yellow know you got like your slope going on kind of got your central crater you know and a person stepped in this so you can see the water pool once he stepped in it to indicate just how water log this is interestingly enough uh all of these lines you see here are basically extremely small patterns it's a dendritic a radial dendritic pattern and it's in a sense effectively Ultra tiny braided Rivers which is something we're going to talk about in the Hydra ology lecture uh couple of weeks from now now it makes s some pretty cool pictures like you see on the left but it can also have some direct implications like the picture on the right where it causes the contortion of the subsurface layers uh especially as some of that material is just being spit out elsewhere you know you're having less you know in another place and so you can create kind of like a sinkhole effect it's not really a sinkhole a sinkhole actually has a very specific definition but it creates like a like a sinking ground effect and as you can see with this car on the right you know that could become problematic imagine that happened when you're driving you know you could potentially be well you would be in an accident the most destructive consequence of tsunamis um besides you know the damage caused by the actual shaking which that that direct damage caus by elor shaking will always of course do more damage and cost more money but of like this you know additional damage the most destructive and perhaps most terrifying of them all is going to be tsunamis and so a tsunami is basically what occurs when something happens underwater like under the ocean specifically that moves a tremendous amount of water so for example uh we often see this in like Mega thrust faults you know like with those subduction zones where let's say you have like a 500 mile wide block of rock uh that you know extends out for a while and you just suddenly let's say 100 ft out into the you know ocean floor and you just take that 500 mile long 100 ft wide block of rock and you just lift it up an inch just one inch I mean that would still be a sizable earthquake but you're suddenly moving 100t wide 500 M long block of water up an inch that is a lot of water displacement and that's going to create a very very large ocean wave and we call those very large ocean waves tsunamis now that's one way to create it is you know just by that direct uplift of the rock or conversely the direct dropping of an in inch by a rock you're just causing the water to drop an inch both are going to create the wave another and probably more common way to create tsunamis is the shaking you know of the earthquake causes an underwater Landslide you like a mega Landslide and that like Mega Landslide pushes a ton of water quickly and some of those like underwater landslides can like move like hundreds of miles an hour you know so they can move a lot of dirt slash a lot of water that's in front of it very fast and so these waves are going to move out in all directions from their source and when they do you know they can be dramatic now interestingly enough um if you were to like let's say you're in the middle of the Pacific Ocean and a tsunami hit you you probably wouldn't even notice because in the middle of the very deep water the wave is going to be very stretched out and though the water is going to move up some distance you're not going to necessarily notice because pretty much it's going to be a situation where like the whole ocean around you it's just Rising and then falling and it's not going to rise as high as like let's say a doom State movie because the W the energy is displaced in a way because of this super deep you know ocean floor there have been cases where there have been like military like American military ships that you know the people on board didn't feel anything you know maybe like a little motion but you know nothing they really expect more than a wave except their instruments indicated that the actual total displacement was enough to indicate and it was quick enough to indicate it had to have been a tsunami and then they could radio ahead to Shore and say oh crap a tsunami is heading your way prepare to evacuate you know and um tsunamis when they're in the deep water can travel super fast so they're not super high but they travel super fast but as they approach the shore you know the wave bottom actually hits the floor and it pushes them upward you know like guess so as the ocean floor gets shallower you know as it approaches land you know all of a sudden that wave bottom is hitting land and the land is pushing the water up and so those waves get much much bigger as you get closer to land until they eventually crash like imagine like like the breaking of a wave a surf you know it's kind of that same idea um and by the time they hit you know shallow Coastal Waters they can be pushed up tens of meters like so 10 meters to put it as in perspective is 30 ft so a 20 M uh uprise would be a 60t actually it' be a little over 60 ft increase or in height so imagine you're at the beach and you see a wall of water rushing towards you super fast well pretty fast at that point it slows down as it gets higher uh rushing towards you that's 60 ft tall I mean if you get hit by that you're you're done you know the picture here is of a tsunami hitting a part of Japan uh and you can see how it like topped over not only like like the basically their ocean walls like it's like a these are walls that designed to break you know potential dangerous waves um in reality there would have been like a cliff beneath there a little bit but you can see that it's quite high and you can see that by scale by those you know those uh PS and the trucks for scale so it's not like crazy high but you can see how it's moving that van that pretty much anything it's path is going to be picked up and carried along for the ri they're super destructive um like they're super destructive on everything they hit now because you are my precious precious students and you're taking my class I want to give you guys a bit of warning if you are ever like like a like a hint you know to help keep you safe if you're ever at a beach and you know you're seeing the W you know the way waves and the water kind of lapping on Shore and all of a sudden it looks like like the ocean's receding like the waves and the and the shoreline is like like the water is like receding away from the shoreline it's like kind of going back to Sea almost like the ocean is draining Run Drive get to High Ground as quickly as you humanly can if if there's a a very tall building nearby get in the building and take the stair SL elevator ideally elevator up as fast as you humanly can I mean serves are good too you know you can in most cases you can run upstairs faster and just don't stop until you get as high as you can if you there are no tall buildings run or ideally run to your car and get in your car and drive towards High Ground as quickly as you can because when a tsunami approaches it looks like the ocean's receding because remember how I said like those type of earthquake waves are like ocean waves and it goes in circles you know well as that wave is approaching in order to get high that wave is sucking the water in front of it of course it's just spitting it out behind it but it's sucking the water in front of it and those waves are so big that it'll make it look like the ocean is receding it makes a shoreline approach and like that super destructive one that hit like all those you know Indonesian and Pacific Islands a couple years back I saw a documentary on it it was actually a very interesting and very sad do documentary and kind of frightening because all of the video in it was taken by you know people on vacation it was like people's video or vacation videos that they compiled together into this like really sad documentary and you know there was like one case you know where you had some guy on the balcony of obviously some sort of high-rise Resort and you know he filming the ocean and all of a sudden you see the ocean Retreat and you just see all the people on the beach like running out of the water like curious and he's shouting like get away get away get get into the building get into the building he's screaming this as loud as he can but he's at the top top of a very tall building no one's either hearing or listening to him and then like I mean he must have been like I don't know I'm guess guesstimating 60 feet high you know 70 ft high and all of a sudden you see a wall of water hit and it pretty much got to his balcony like he had to hold on you know so that's scary and if you get caught in the Bel the wave I mean if you don't get crushed you know if the wave doesn't pick you up and crushed you against something it can hold you under long enough they could drown and if you don't drown you can be caught up in a rip current and it could be bad like um there was uh one of the videos uh that was shot in that documentary one of the people you know it showed them like you me they kept it running which I I wouldn't have done this I'm not this dedicated but they saw the way of approaching they started running and they started running upstairs you know and they tried to get into a room but the wave caught them and they kept on filming and of course once the wave hit them it smashed them and of course you saw like some footage as the waves kept on carrying the like smashing the camera around now somehow people somebody was able to actually retrieve this camera and apparently it wasn't completely destroyed that's how they got the you know the film but the people who were in the room they actually traced the camera to the people who owned it and those people what ended up happening is the wave after it crashed it carried them almost a mile offshore and like one of the people I believe had like a broken arm if I recall correctly and the other person had a broken pelvis and they actually blacked out like they when they they blacked out and they came too like a mile offshore bobbing to the surface and obviously an excruciating pain and they basically both grabbed onto some like just random trash like you know to like try to help stay afloat until eventually you know because I mean there's no way they're going to be able to get back to shore until eventually somebody came on a boat and you know helped them you know so it is just and I guess to me it's just absolutely amazing in in like all inspiring intimidating just how massive and destructive geological forces can be so this picture here I think showcased you know the you know the evolution of a tsunami pretty well you know so you have like that subducting plate let me get some colors here it's ating plate here and so you got like you know you got your bending off Zone here but basically you know where like that direct contact is near the surface you can create like that that shaking SL displacement and that's going to be where your tsunamis originate so notice how you know though you have your content plate um like all this would be your continental plate you know your overriding plate you know you can have it extend underwater for quite a while because of something called the continental shelf something we're going to talk about later it's Continental Rock it's just currently not quite high enough to be above sea level um and so notice how it doesn't look like these waves are particularly tall I mean they're reasonably tall but it doesn't look that tall and they're super wide so where they're forming when they're in the deep water you know they could be moving at 800 km hour that would be about 480 M hour give or take um now as it's propagating towards land and it gets closer to the shore then it's going to start hitting the bottom you know the the wave base will start hitting the bottom of the ground and so at that point in time it's going to drop in speed to about 340 km an hour or in other words about um I'll give or take 190 miles an hour I'm going to be a little off on that number by maybe 10 miles um and that's going to be when the water dust is at 900 M deep that's like again like 2700 ft there um and then by the time it approaches Shore it's going to be traveling at about 50 km an hour or in other words about 36 M an hour so fast but not devastating fast at that point no faster than we can run certainly and that's going to happen when it's near the shore and so the reason it's slowing down is because of friction like that wave is like um let me try to draw this in the water so kind of like those Raleigh waves it's basically actually I'm doing did backwards there it's like this and ultimately it's propagating forward that's again why you know it's sucking the water in um and uh and so the part the water as its motion moving on across the ground it's it's like anything hitting another surface you're going to have friction and that friction is going to slow it down but of course the water behind it's moving faster so the wave in front is moving slower the water behind it's moving faster so it's going to catch up which means that the distance between waves gets smaller and more importantly for specifically for that tsunami wave is you're adding in more water and you're having less un you know space underneath the surface so it's going to be pushed higher and it's going to make bigger waves you know near the surface and so these things are going to occur when you have like um it's basically part of that elastic deformation and the bottom picture here I think showcases it quite well so you have what's called like a locked Zone like right here so what ends up happening is a plate is subducting it is actually actively going down but the overriding plate and the conducting plate are locked so tightly like the crystal bonds like the chemical bonds between those crystals are strong enough that they're not breaking so it's going to warp that overriding plate and it's kind of like bending the stick and when it does finally break it's going to just snap up kind of like you know when that brake finally the stick finally breaks you know like it just snaps really fast and so when that piece of the overriding plate snaps back up to get back to its original shape it's moving a lot of water really fast right the last thing we're going to talk about for this lecture is going to be folds and so um folds are going to be uh structures that are formed by ductile deformation and though it is possible to generate folds by uh like um self- sediment deoration and things like that we're not going to concern ourselves with that here what we're going to be talking about are folds that are going to be caused by compressional stress so the definition of a fold is going to be wav likee undulations that form when Rock bends under compressions and sometimes they can create very simple wav like patterns kind of like you're seeing here and some cases I can create extremely complex patterns and in some cases they can create patterns so complex that we're still like uh what's going on we don't get it and so you're going to get folds specifically when you have compressional forces as a result of two plates colliding or something or some other event that is causing compression and the reason why you're only going to see it there is because that's the only way you're going to get those kind of forces you will get forces are folding in the asthenosphere absolutely but the asthenosphere is so deep it's rare it gets to the surface it has happened so we know it's true you know especially when you're dealing with things like your nice you know some of your nices and whatnot and your migmatites um but these are rocks um like specific types of metamorphic rocks but the um the only way you're going to get folds anywhere near the surface is if you have something squeezing them on the sides to add enough additional pressure like you know to allow the rock to flow as opposed to break because remember a rock wants to break a solid rock wants to break when you get super deep you know it's still a solid rock but if it's under enough pressure it will simply flow and bend instead of break and so um just to repeat the idea you know if you have enough compression going on if you have something squeezing that rock from the sides that can add enough pressure to allow it to flow instead of Break Even though it might not be deep enough to do so normally so that's why it's always going to be compression yes I repeated this a lot but it is an important point now you have different types of folds and we're going to talk about these different types of folds um and so the first type is going to be an anticline and an anticline is going to be where like the arch is folded up so like it's convex up you know it's like an up folding of the layer and a sincline is going to be where uh the it's convex down you know it's going to be like a downfold or trough and you're often going to see these things in association with each other because again you're squeezing it like uh imagine you have like you know a block and you squeeze it on both sides actually it might be easier to think of this with a a stick so I'm going to try drawing this again with just a purple stick so you have a nice straight purple stick oh that's a blue I guess and if you try to squeeze it then it's going to crumple right you know now obviously I'm extending this stick greatly but you can kind of get that idea that it's going to crumble and so that's going to be your your anti cines and your sin cines now there's a really simple and helpful trick to help you remember and so I'm going to draw this out so I'm sorry but you're going to have to live through more of my bad art but like I said you're going to have your as it bends you're going to have your convex up your convex down your convex up you're going to have this like wave like structure and so the trick to remember for this is your convex up is going to be in anticline and I remember this because the a is pointing up and the convex down is going to be your sincline and I remember this because the Y is pointing down pretty cool huh simple easy so this is going to be a picture of like uh some anti cines and sin cines so the middle picture which we're going to start with is going to show you like how like the squeezing of these rocks have caused it kind of buckle a little bit and so it can fold up and folds down and folds up and down and notice how you got like some you know in this case is folded enough that it started to overturn a little bit and so you're going to have an anti clim its convex up a sin clim its convex down and you're going to have an overturn antic cine or an overcurrent Sinn cine depending on the shape you know if it's tilted and if it's completely tilted it's going to be called it's going to be like fully overturned uh we call it a recumbent fold and so the pictures on the top are going to be like an actual you know example of different ones of these so the top or the first one on the left is going to be you know your anticline notice convex up like an a your middle one is going to be your sinine notice convex down like a y and your overturned limb you know like your in this case it's an over or uh an overturned anticline is kind of like tilted now geology can get really really complicated in this context and and we're not going to go anywhere near this complicated in our class but I do want to kind of share a cool story about this so there is an area in California which is quite possibly and definitely in my opinion the most complicated terrain like piece of land in the world like the geological history in that area is so complicated that most people don't know what the heck's going on like if you look at geological maps and uh they usually know exactly what rocks are there and in this part of the land in California like there are areas that are just sort of kind of have a data light around them and it just simply says um um uh U sorry UF which simply means undifferentiated or UFC undifferentiated Franciscan complex and we call this BL Land The Franciscan complex and yeah it's it's around San Francisco but it extends Beyond it it's more than just the San Francisco region and it's because you have like so many things tectonically that happen in that area that it's very hard to make sense I had a friend who looked at a geological map and saw an area of it that just it was like oh like you know 5 6 miles long and maybe 3 4 miles wide and it just had like a DOT line around it and it just said undifferentiated Franciscan complex meaning they didn't know what was what exactly happened there and so she went out there mapped all of the rocks in that area to try to recreate what happened there and just the mapping and recreating of that 3 m by 5 Mile area I might be a little off on those measurements but it's about right um was enough to get her a master's degree in geology that's how complex this is my own personal story regarding this was this one piece and let me try to explain how this rock form this is what we were able to reproduce so kind of put your arms beside you you know going flat so like you're making a long line with your arms one to the right one to the left you know so that's kind of Imagine as like a bedding layer like so your sediment your dirt was laid down flat your rock was laid down flat there and then it got squeezed and when it got squeezed you know it formed a like a u-shape you know a sink line right you got a u going on and then like you know differential Shear caus that U to rotate over and become a c-shaped and then that c-shaped then warped into a brand new U shape and so all we know is we have to look at all these different rocks and look at how they're angled and how they're related to each other and then you know maybe do some age dating to figure out how old they are so we know which is the oldest which is the youngest and and then from there try to recreate what happened like in what order it's it's complicated but it's kind of like a giant you know geological jigsaw puzzle it's really is kind of fun to try to recreate this stuff and we do have some pretty cool tools to help um especially when you get like things that try to like you know trick you you know like so for example you know you might have a situation where you have like layer a and layer B and then you have like a fold or start it's a tilt kind of like that you know folded thing so it's like that so again you have a at the top and B at the bottom but eventually and I'll switch to Yellow on this one um actually I'll just I'll stick with red um eventually the whole thing can kind of rotate over and so over here on the left you could actually have a situation where it looks flat when you find it but in reality it's flat because the whole thing turned over and so now the oldest is on top you know paradoxical um stratigraphy is what we call that sometimes over turn strata would be the uh actual term or another term we use and so it's so we have to look for things like geop pedals to determine which side was originally up and there's like lots of cool Clues we can find and it's it is actually surprisingly fun so this is a picture of Rainbow Mountain and believe it or not this place actually exist I found this picture and I thought Photoshop fake because like it's a absurdly colorful this place actually exists now in this particular picture that I have um they used a a technique to kind of saturate the colors a little bit more to make them look brighter Because the actual picture was a little bit washed out because it was foggy and gray this particular area uh this is in South America by the way this particular area it is often times very gray and Misty and foggy because of how high it is and so most of the time people take pictures and the colors are a little bit washed out because of that effect so a lot of people will you know saturate the colors a little bit more to make them know a little bit more bright but yeah it really looks like this so the question becomes what kind of structure is this is this a fold yes but what kind of a fold and the answer is going to be an anticline because it is convex up like a giant a now beyond all of this you can have additional structures called domes and basins when you have this folded warping so you can imagine anti cines and S clients and all their you know relatives as being like a two-dimensional structure so imagine you have like like a piece of paper and you're holding it flat in your hand you know like with one hand you know like in front of you with one hand on each side and then you put your hands together the paper is going to fold right and it's either going to fold up or it's going to fold down you know depending and so we draw that as that simple like oh oh that's try not yellow as this simple you know kind of structure like it's going to fold up or down it's just a simple structure but in reality it's more like a sheet you know like if you're looking at an edge on yeah it looks like you know a line going up like like an A or U you know but if you were to kind of tilt it a little bit you'd realize it's a sheet it' be like a hill but and and that's because the rock is folding along a single axis like you can draw like an imaginary line um between you know from the high point or the low point and of course I'm drawing a little off cuz I'm not a good artist but you can imagine that's like your fold axis and it's like that sheet of paper is folded around that axis so it's even on one side or the other you know and and it's like a sheet now instead of having it fold it along like that axis imagine you took your sheet you took your finger you're holding it in one hand and you put your finger in the point or the tip of your finger in the center of the paper from underneath and then you took your other hand and you sort of push down so that the paper wrapped around your fingertip so in this case instead of creating like a nice like sheet like you know a or U shape it's going to create more like a bow shape and that's basically what these are a dome is like an upside down bowl and a basin is a bowl you know so that's a good way to think about it a basin is a bowl and a Dome is in I'll change this to Red so to distinguish it a little bit easier it's going to be an upside down bow and that's just the easiest and best way to think of it now we can often identify domes and basins you know you know in the ground based upon the Rocks so for example uh in this particular case you know if we walked around and we mapped all the geological rocks you know we might notice that we have like a very like a one type of rock you know that we age date to know as the youngest on the outside so this rock out here is all going to be youngest Rock and we notice we have a ring of rock inside it you know like this that's going to be a little bit older and then inside that we're going to see another ring of rock that's going to be a little bit older still and inside that you know we're going to have the oldest possible rock you know we date those and that's going to be the oldest this by the way this is Mount Rushmore in South Dakota as if you're looking down from above although it's like the region that contains Mount Rushmore like Mount Rushmore is just one of these little points like right like right uh here I mean how I drew it is actually bigger than what we're showing to put it in perspective we talked about MTH scale I mean 20 miles right here is that that's the distance of 20 miles so when you see a situation where the Rocks get progressively older as you go into the center of that Circle then we know that's going to be a dome and so you know if you have that XY you know what's we call like a transect kind of Crossing this thing here we can use that to create like a side view profile which is shown on the bottom here you know so we can kind of see that and the reason why it's not a perfect circle is because you know the ground was exposed unevenly and they weren't necessarily flat to begin with you know so those like Nature's nature those discrepancies now conversely if we saw the opposite or as we got closer to the center of the rock the uh the or Center of that structure The Rock got younger then that would be a basin so a basin the youngest is in the center a dome the youngest is in the or the oldest is in the center pretty cool huh all right so the rest of this class is going to be over concepts of topography and cartography where cartography is going to be the study or not study but it's going to be the idea of map making and the studying of maps and topography is going to be dealing with the actual shape of the land so where topography and cartography meets is basically trying to take that three-dimensional surface the Topography of the land and trying to translate it it into a two-dimensional map so map making has been around since Antiquity you know I mean people have been making Maps pretty much since they started drawing you know but uh but they've been finding better and better ways to really kind of represent them and to do them through time now the ability to read a topographic map is actually a pretty good skill to have and if you get some experienc reading topographic maps you know you'll start getting to the point where you could actually look at it and start determining like a lot of its structures in three dimensions just out of glance uh and on top of that when you get really familiar you can even start determining features of that landscape Evolution uh so for example you know if you if I saw something like some sort of uh feature that looked like this with the contour lines then I would know that there was some sort of either Valley or Stream Valley or something like that there and if I saw something where it went a little bit down like that so uh where it's the same you have that kind of upward and then that set and downward that would tell me that uh you had some sort of a valley that formed there but then there was a landslide and I can make that determination of not just the shape of the land but also the evolution of that land at that exact place just based on how those lands are pieced together and that's really just comes down to experience and hopefully you guys will actually gain a lot of that experience between this lecture and next week's lab you'll have a better appreciation of how these things work nowadays we have modern computers and modern computers can do some really cool things to make reading Maps a lot easier and the most powerful of those tools is probably going to be the hillshade and the hillshade is basically um applying a shadow effect to each pixel based upon its um elevation and so we can do this in with tools like arcgis you know Geographic uh Information Systems where we where we can actually say like where every Point like every pixel on that map what its elevation is and so the computer will read it as a three-dimensional surface and then it will apply a like a sun Source you know in this case it' be in the top left and then apply Shadow as if there was a sun shining down and you're looking down at it from above and so this creates like a kind of a three-dimensional view so you can visualize these things better and so like in this case you're looking at um Yus Valley and you know it might be a little obvious because it's you know written right here but um but even if you didn't know a specifically yosity you know you can see you have all these tight contour lines here indicating like steep surfaces framing you know this internal area like here that has relatively few contour lines meaning it's not you know it's going to be flatter but you can see it much more clearly in the map on the bottom right you know where you can see like the shape of all those mountains and kind of that deep valley that's almost flat this is a topographic map of Mount St Helens and so you could tell that there's some sort of structure here just because there's like a certain symmetry to how these lines are going you know that kind of ring or circular type structure but you got like this weird like stretching out of the pieces here you know whereas it seems really uh consistent the rest of the way around and much denser here closer to the center with it being almost nothing at the dead center of this map so I mean I would look at that and I would say all right you got some sort of General incline up and then a sudden change in elevation and looking at those numbers it means a sudden change of those elevations going down so and then you have like a relatively gentle slope you know in this area but if you apply you know those computer algorithms you know those Hill Shades you can take the same map and get a pretty good three-dimensional view so you can see what you're looking at is a top down view of a volcano where you know you have the mountain kind of going up like this let me change my color real quick kind of going up in this direction and then you have like the sudden down you know and where you have like the basically the crater of the volcano with a slight new like basically that's the uh start of a new volcanic Dome forming inside the crater and that weird looking thing in the top you can see is just an area where when this volcano last erupted it basically exploded in such a way that it blew away its entire North Face and so it's just kind of a much more gentle slope down because most of the mountain on the North side was literally blown away so we're going to go into the different ways we kind of we divide the world into units and and how those units can be used to kind of locate where you are where you are on the planet uh and so I want to go with this picture first that's showing you know the prime Idan which is that straight line up and down uh as well as as the uh the tropics uh the tropics being uh at 23 and 1/2 de North and 23 and2 de South um and those the reason why I wanted to mention those beginning you know with the it being bisected the world being cut in half at the equator because those are going to be your subsolar points meaning it's the hottest places on the planet in terms of the amount of direct sunlight received and it's uh hot because the Sun's rays will be the most direct there we're going to talk about um atmospheric heating later on in the semester and when we do we'll cover the uh the idea of the subsolar point and how the angles of light can actually influence the temperature so if we go to ancient Greek times Aristotle divided the earth into zones based upon their climate now which wasn't a terrible way to do it and his idea you had like the Tor Zone which is the areas between the tropics you know the area highlighted on the map here uh and it's called that because of the area's effectively endless sunlight and hot temperatures from the uh endless sunlight and he called the areas above the Arctic Circle and Antarctic Circle which would be um basically above there and Below there he called those The Frigid Zone because they had so little sunlight that they were very very cold um now depending on the the ancient map you look at you know the tropics sometimes are not the exact same as the tropics weine them as now but the principle still stands since then we have developed a latitude and longitude system where your lines of latitude are going to be the divisions north of the equator and south of the Equator and your longitude are going to be your lines you know your great circles your lines that are running uh east of the primeridian and west of the Prime Meridian and I'm going to go into each of these in detail in a moment but I do want to say that lines of latitude have been known since Antiquity basically because lines of latitude are effectively just the angle from you know of the Earth from the based on the equator like how many degrees north or south of it of it is it from the equator so this is like a unit of measurement that has actually been used for a very long time but the liines of longitude is actually much more recent it was something that came about much later and it came about during the height of the British Empire you know when they basically had an Empire that stretched effectively around the world um but you know uh 1800s uh so after the you know independence of America and the Royal science um Association um you know basically a bunch of Nobles and clergymen and whatnot who you know high ranking people who were really involved in the Sciences uh and um were trying to figure out a way to you know better navigate and plot on maps and so the king put out a uh award you know with through the uh through this organization with the idea being that if someone comes up with a system that is so good it can be adopted then they will win a big prize and I don't remember the exact amount of the prize but imagine it like in today's dollars like a million dollar prize it was something pretty significant and so various people tried throughout the decades and you know nothing significant or substantial AME of it and the person who figured it out was actually a clock maker now this clockmaker was an absolute genius when it came to clocks in fact um he was he made clocks that were so accurate that like there are clock towers he constructed that are still running and still accurate to this day uh and so the um so in the course of his life he kept on trying to make you know improvements to it like um but he had this thought like or but he had this thought he thought you know what we Define by noon as the point when the sun is at its Zenith you know like when the sun is directly above us we call that noon so he thought that if boats could have a clock that would let you know um exactly when it was noon you know in England and you could see where the sun was in the sky you could use that angle to calculate you know where you are in in the world BAS basically this is how the idea of longitude began the problem though was how did you keep track of time on a boat and so you know he first he thought of a uh grandfather clock and he actually invented um several really cool innovations that are used to this day that allowed it to uh you know compensate for the the shaking of the boat as well as the differential uh expansion and contraction of the gears based upon like daytime in nighttime temperatures and humidity uh he actually had like like kind of wacky tests where he'd actually build two of them uh and he would put like one inside the house where it would be safe and then the other one outside and he would just sit in the doorway and watch the time go by and see if any differences occurred and make adjustments as needed but the problem though is a grandfather clock on a boat it's just nothing he could do he could make could break the chance of error because it's based upon the metronomic swinging of the pendulum and you he just really couldn't compensate for like the tossing and turning and of of some of the waves and and storms and stuff like that well one day he went to a shop and he saw a pocket watch something he didn't really see before and at that time pocket watches were Uber expensive highly inaccurate and really just sort of a status symbol for the ultra wealthy I mean they they weren't much good for a lot else at that time but he was fascinated so he got one and he studied it and he invented a brand new pocket watch that actually was accurate and was sealed to like you know deal with the vares and vagrancies of the sea and because it did not rely upon um a pendulum you know it it didn't matter if the boat was being tossed around and so his idea to was to um that the captain could again pull out this clock look at you know the time and then look at the angle of the Sun and calculate out where he's at you know in terms of the longitude and then you for latitude you would look at um other things you know to determine your angle from the equator like also the Sun but other things as well um and so he would um so in order for this to work though he had to have a clock that was absolutely accurate and so you know he built a a pocket watch as accurate as he could and then the experiment was he had had the watch put into a sealed box and then he gave the box to a captain who put it on his boat and just you know that's a the captain you know had a trip basically around the world uh and um and the idea was when he comes back he would give the unopened box back to the guy and they would compare the times and so the guy went and months and months later the captain came back and gave them the box and they opened it up and they showed like yeah the time on the pocket watch was still the exact same time shown in the giant Clock Tower and so success so he wrote you know the uh the scientists over at like the Royal Academy uh about his success and all his things and the scientists said or the Nobles I should say said wow that's I guess I could be fast inting but it's really not worth reading or considering because you're a commoner you're not of noble birth so you don't have any understanding of the Sciences so they basically just sort of laughed him out of the halls and he you know started to Fade Into Obscurity but decades later you know when the guy was effectively on his deathbed his grandson was still you know thinking like this Injustice can't stand so he petitioned to have an audience with the King cuz back in those days any citizen could petition to have an audience with the King it just might take a while to get one and so he finally got audience with the King and he explained the whole situation to the king and the king is quoted as saying we have done this man a grave Injustice and then granted him um the reward and at that end basically made the Navy uh and merchants accept his idea as like a new system of coordination and though since then the numbers have been tweaked you know like for example like where is the prime meridian going to be things like that um the principle behind it is still what we go by today all right so going into a little bit more detail latitude is going to be like I said the angular measurement north or south of the Equator so it's going to range from 0° at the equator all the way up to 90° at the North Pole so you can imagine like a line going from like the center of the earth to the equator and then like what angle does that spot on the earth on the surface of the Earth make as you go up you know is it going to be you know zero at the equator or will it be kind of steep at like 15° or will it be you know 90° at the poles and you can imagine this like you know the surface of the planet and so we specify you know nor North or South so we because you know you have 2 45° you have 2 90° so to specify exactly where it's at we just simply say it's like you know 45 de north of the equator 45° South things like that now every line of latitude is going to be parallel to each other so they are all forming Giant Circles and the big circle like the great circle is going to be the equator a great circle is a circle that cuts the world in half and all of the other lines of latitude will be considered small circles now the small circle at 90° is going to be a point because at exactly 90° it is the literal top of the world now your lines of longitude are all going to be big circles and that all of them are going to uh BCT the world but we calculate them basically uh from 0 to 180° um from the prime meridian meaning we pick one of those lines um I guess I should say a line of longitude is called a meridian and your Prime Meridian is going to be where the Meridian that has 0 deges so you kind of think of like the equator for longitude uh and so it's you have 360° to go completely around the planet because there are 360° in a circle right uh and uh but we instead of doing it from 0 to 360 we do it from 0 to 180° but we specify if it's going to be east or west of the Prime Meridian now the the Prime Meridian is arbitrarily chosen like the equator is simple because that is the point where the north is evenly divided from the south you know it's spling the world in two but since every line of longitude is technically a great circle you know there is no natural starting point so uh in the early days of use of longitude use every country defined their own prime meridian but in the 1800s by International agreement they decided to make the prime meridian to be the Meridian that goes through the Royal Observatory at green witch and so uh The greenrich Observatory is going to be your prime meridian and this is the reason why um when we talk about time zones Why We call we used to call like time zones based upon its deviation from greenrich Meridian time or GMT now because you know one full rotation of the planet is going to be 24 hours that means that um at any point on Earth you know at some point if you were to go around the planet you'd have to cross a day so we Define the opposite side of the Prime Meridian you know the 180° Mark as the International Date Line and that'll be the point where the day will be officially changed uh so because of that um that the international Daye line does do some you know quirks in order to avoid like having a country have you know be in uh have a have two towns 10 miles apart be on different days so they'll actually adjust it and I'll show that in a moment to create an organized time system you know people divided the planet into to 24 kind of longitudinal zones you know repres each one representing 124th of the circumference of the planet because it takes the planet 24 hours to do one full Revolution and so the idea being that if you cross from one of these zones to the other then you would be going either forward an hour or backward an hour in terms of your relative position to the Sun and so the original system was the GMT or the greenrich Meridian Time be because we defined all time as being either counted ahead of the green witch Meridian or behind the green witch Meridian this is for example why you know uh here in California it might be let's say noon but um my friends in Michigan it would be 300 p.m. if we were talking on the phone now we commonly use the GMT time and most common parament but for the most part we have actually switched over to UTC system which is called the coordinated universal time and like I said most of the time when you have hear someone talk about you know like this number G plus whatever GMT then it's they really meaning UTC and the UTC is actually a very good system because um it can be used when Precision is needed and it technically doesn't really apply to the time zones like the time zones in the GMT system are somewhat arbitrary they are based upon those you know roughly equal you know 24 124 of the circumference zones but the lines that are drawn are often um skewed in order to allow things like certain countries or certain States or certain Island chains to all be within the same time zone Zone because you know it could be inconvenient having a state for example have two M two time zones in it when sometimes you can't get around it but they do make efforts to avoid that whereas uh Universal or UTC according to Universal time it's going to be the more precise one it doesn't really care about those um divisions I mean sometimes they'll still count it CU like I said a lot of times we're using UTC and GMT kind of interchangeably but UTC is based upon atomic time you know we have an atomic clock and uh it's basically guaranteed to have an accuracy of 1 second you know anywhere in the world and so this is really good for things like the internet you in the internet we call it Network time but Network time is UTC and that's why like you know in theory um stand like time set across a whole of the internet is standardized planes have to use the UTC system because you know they don't need to know what time of the day it is on the ground they need to know the exact time it is relative to again the greenrich meridian line in order to uh assertain their location in three dimensions very clearly because you know otherwise they could overshoot the airport same with boats and spacecraft and things like that so this is a map of the different time zones kind of colorcoded so you can see that you know there's a lot of skewing going on in order to keep you know States or countries you know entirely within one time zone and note that uh your uh Prime Meridian is going to be rate about here and your International dat line is oh I'm sorry right here and notice how you have like these kind of like for or right word skews that's just to make sure that certain countries will be permanently within uh the same date range it should be obvious that you know if you have you know 90° of latitude up and down and and you know 180 degrees of longitude left and right that every degree would still represent quite a few miles so what do you do if you need higher resolution and so there are basically two ways you can do that and the first one is going to be the original and the one that's still used in many places today and that's going to be your clock like division where every degree can be divided into 60 minutes and every minute can be divided into 60 seconds and so we use kind of a notation of this of where you have 60 minutes with like an apostrophe it's going to be your 1 Dee and your 60 seconds so like your quotation mark is going to be 1 minute and that's going to be like how we divide it up nowadays in our more computer sounded age we often would do what's called decimal degrees which means we completely ignore the whole minutes and seconds and we just talk about it in terms of tenths or hundreds or thousandths like if um like in my job when I need to uh catalog the location of a fossil or an artifact you know I use a GPS unit and I measure it in um decimal degrees and I so it'll be like this many degrees and then like point and I usually have it to like seven or eight decimal places which will usually uh narrow it down to its location on the planet to either a few feet or a few inches in some cases it can go go quite a bit deeper than that you can actually have decimal degrees all the way down to submillimeter if you wanted to and so we kind of doing that more frequently in the computer age but uh minutes and seconds are still widely used and they have been the traditional one now you guys may be wondering why is it that it's 60 you know like 60 Minutes 60 seconds why why is a clock you know 60 minutes and 60 seconds and why is like a circle 360° you know you might be wondering things like what what what Define this and this actually dates back to an ancient numbering system this is just going to be kind of a fun fact for you guys but um right now our entire numbering system is base 10 you know so it's like 1 to 10 and then like 11 12 but you know the 13 14 you get to 20 that's 21 22 31 32 so on and so forth it's all on a base 10 numbering system but in ancient Babylon they actually had a base 60 numbering system and so because they also created a lot of the geometries that governed early um circles and whatnot we often retain that original system where circles are divided um on units of 60 so a circle is six units of 60 or 360° um and and or subdivided like into like 60 Minute division 60c divisions things like that it's all a function of that original b60 system used in ancient Babylon so a map can be really anything you can make a map of your kitchen you can make a map of the Stars it doesn't really matter but you know when we're going to be talking about maps in this class we're going to be talking about maps of the land you know of of an area and so the most common type of map that we use is going to be USGS quadrangles you know call that because they're produced by the USGS which is the US Geological Survey they have quadrangles for every spot on the planet right now and it's kind of the go-to reference and there are two types of USGS quadrangles you have the 7 and 1/2 minute ones notice the markings down over here um or it could be a 15minute one and so that's really referring to like uh how much longitude and latitude it's covering there is another type of system that we use um I haven't actually seen it a lot um but it's actually very commonly used in the military and it's also commonly used in archaeology and it's called the UTM system which stands for the universal transverse mercader and I actually kind of like the this idea this way of doing it cuz I think it can create really accurate measurements and so the idea is that they divide the world into 60 zones roughly corresponding to 6 degrees of longitude each and so like on this map on the left you know one the uh New York one the one that's in yellow right around here you know that would be for example one of those systems and so um and it actually has like a some kind of fine-tune stuff in there to avoid Distortion because it's based upon a uh a transverse cone projection which limits Distortion because when you translate a sphere into a flat map you're going to always get some Distortion that's why often times like Greenland looks like it's like almost the size of the continent or the North America because uh because of that Distortion so the UTM system actually has metrics and way using the uh conic transverse projection to actually avoid almost all of that Distortion as a result it excludes the polar regions so um like the very far north and the very far south because it would be impossible to properly correct for those distortions so they actually just create two new systems like in the UTM system like two new zones specifically as like a conic look down upon the poor regions um and it's actually really cool now one of these zones will cover like the whole you know North to South Range you know North Pole to South Pole so to compensate for that we'll often when we use UTM systems we'll specify you know uh the zone and then whether not it's like north or south of the Equator and so the idea behind um locating yourself is you basically State the uh the Zone you're in the UTM Zone you're in and then you state how many meters north and east you are of the um of the origin and there are like really kind of complicated rules regarding how they determine Origins but you can kind for like Simplicity sake you can kind of picture it like the bottom left you know like the equator and you know the Eastern portion there is it's a little more complicated than that but that's kind of an easy simple way to picture it and so I like this system because it can really zero you in like to an extremely fine degree or fine level of precision now let if you do decimal degree lat long that will actually get you the same level of precision but it does have that potential problem of um Distortion so when we were doing Arch ology we usually did the UTM system because it is very accurate and very precise when you're dealing with a very small region like let's say an area the size of several Farm Fields you know uh it does start having problems when you start dealing with really big areas like the entirety of the US but it's a it's an interesting system and you will sometimes see it um you know like UTM Maps uh in certain areas so now that we kind of covered you know what maps are and you know how we Define them and all that other stuff I want to take a moment and talk about some of the things you're going to find on a map and so the first thing I want to talk about is your declination and so your declination is going to be a value that will be listed you know usually in the bottom often to the right or the left of the scaleb bar and you'll usually see something that looks like this this where you'll have something like that and there'll be a star here you this left one may not be here but sometimes it is it might say GN and whether or not that left one is there you'll have something that's like MN and so the star is representing True North meaning that's the direction of the North Pole and so in the pretty much around the world it's uh the USGS in particular um sets it so that the maps are oriented such that North is up and then the one on the right MN stands for magnetic north and GN stands for grid North so I go and write that down and that has to deal with uh correcting for the Distortion in a UTM system we're not going to worry about the differences in Grid North we're just going to R doesn't exist for this class but magnetic north is important because that's going to be your declination and what your declination is is going to be the difference in angle between true north and magnetic north because the way we try to determine what direction we're facing when we're actually out in the field is we use a compass and and we use that to see which direction North is or which direction we're facing and it'd be great if the North Pole was magnetic north but it's not uh so like uh I believe at the moment magnetic north I think is somewhere around Eastern Canada like you know very North but Eastern Canada uh and so there'd be some degree amount so it' be some you know like degree you know let's say 10° and 6 minutes or whatever you know they they'd have some you know specification and so that is B basically saying that if you're in the area depicted on this map you would need to adjust your compass by that many degrees so that when the compass shows you're facing north you're actually are facing True North as opposed to magnetic north and so there's not a single number for this like magnetic north will be a different you know your declination for magnetic north will be different in California than it will be in New York state or than it would be in England you know because it's all because that magnet North is always going to point to that Magnetic North Pole and so your relative orientation to it is going to differ based upon where you are on the planet now often times when you are actually going out hiking and you're looking at that declination to correct your compass take a look at the age of the map because the Magnetic North Pole doesn't stay put it actually moves around it's something we call the drunken walk because it's literally just sort of migrating randomly around the North Pole the True North Pole uh and when you we we've actually plotted that the Magnetic North Pole accurately since Viking times and when you take all of those points and you put them together it looks like somebody doing a drunken walk now interestingly enough if you took all of those points like every last one of them and you averaged their locations together it would average to the true north pole but at any given time it's not it's just taking a drunken walk somewhere so usually if you're looking at a map that's more than 10 or 20 years old you might want to consider getting a new map to determine the declination or go online and take a look you know that information is readily available online right now and so it it's just one of those really important things to know to make sure that you are orienting yourself correctly if you're using a map and a compass in order to determine where to go because if you're like you know five deg off that could and you walk from several miles you can end up quite a ways away from your destination so another part of a map is going to be the scale and the scale is going to be this comparison like the ratio of distance on the map to distance in real life and so there are three different ways that you can really Express this you can have the ratio so like 1 to 24,000 or you can express it as a fraction like 1 over 24,000 they both mean the the same thing it's just how you're expressing it and or it could be like a bar you know like some sort of visual scale which means that you know you have a a bar unit like drawn on the map with a depiction of exactly how much distance that's representing and so a bar scale is usually pretty good because if you you know shrink down the map or you scale up the map you know you'll also be shrinking up that bar scale so that you know it will always retain its you know consistency with regards to the map but I usually like to do you know like the ratios of the fractions so a common ratio is going to be 1 to 24,000 because that's translates you know one unit whatever unit you measure on the map is going to correspond to 24,000 of those exact same units in real life and so the reason why 1 to 24,000 is a common ratio is let's say you measured an inch one inch measured on the map represents 24,000 in of distance in real life and 24,000 in is 2,000 ft that's just a pretty convenient scale now when you were talking of maps we can talk about them being large scale Maps or small scale Maps but this is where it gets kind of weird because a large scale map is a map that actually has a smaller Ratio or a smaller fraction meaning that it's covering a smaller area and a large scale map is a map that has a much uh bigger number on the bottom and it's covering a much larger area so for example a 1 to 200 would be a large scale map because uh if you compare the fractions 1 over 200 versus 1 over 24,000 obviously the 1 over2 200 is a much bigger thing I mean I guess another way to think of this is what with simpler numbers is what would be a bigger value 1 over two or 1 over 20 1 over 2 is is 50% it's 0.5 1 over 20 is 5% or 0.05 you know so like let me go and draw this out so 1 over 2 is 0.5 and 1 over 20 is 0.05 and so you can see that the 0.5 is a bigger number that's why we call it a larger scale because the fraction is a larger or bigger number and so you'll usually use large scale maps for very small regions like a house a room maybe a neighborhood you know things like that and you use your large scale maps for things like cities and states and countries you know so I mean it's really just you know the size of that fraction so as I've repeated several times so far a topographic map is a two-dimensional represent resentation of threedimensional space so the question becomes how do we actually represent you know that vertical rise on a flat surface and we do this by utilizing Contra lines to show the elevation of the area like how high it is and so a contra line is basically a line drawn on a map that is representing All Points of equal elevation in other words let's say you Orient yourself you know you have a map on hand in your compass and you're in nature and you Orient yourself so you know that you're standing on the contour line drawn on the map if you were to you know make sure you follow that contour line like that you never took a step you know away from the Contra line as you walked around you would be never going upward or downward you'd be walking in a perfectly flat level so you can kind of picture it like these there's a picture below here you know where you have like a mountain shown on the side and you're dividing it into these like you know equally spaced know planes and each of those planes is representing a contra line so where that plane intersects you know the surface you know the mountain where it goes up you know you would draw a little circle and so you can create your cont map shown on the right to indicate that shape that mountain shape and the distance between these um between these cont lines like the vertical distance is going to be your Contra interval that's like how far you have to go up or down to get to the next conture line so elevation is going to be the distance above sea level now I will say that sea level is also a bit of an arbitrary abstraction because there is no actual definitive sea level like um in fact if you think about tidde sea level actually changes every day doesn't it but on top of that some oceans are actually higher than others one of the uh issues they fac when they first started building the Panama Canal was the fact that the water in the Pacific like the sea level at the Pacific was actually higher than the sea level on the Atlantic side and so they had to create a system of locks to like they kind of like control dams with gates to like uh create that Canal going through Panama and the um so in order to kind of create this idea of sea level what they did was they created um sensors to kind of show like you know where sea level is at like so like what is my elevation you know relative to an arbitrary datam such as like the center of the earth and where's this where's the surface of the ocean at and then they took measurements you know like once an hour or so you know 24 hours a day amongst thousands of places around the planet they put these devices like in thousands of places around the planet and then they like I said they were taking measurements pretty much on the hour every day for 17 years and they took all of that dat data of of that elevation and they averaged it together and they call that elevation sea level so it's actually possible to have like countries like the Netherlands which are officially below sea level uh and you can have uh I've seen Maps where um you know where you know those areas that are marked below sea level but it's Solid Ground because you know during low tide that area is exposed to air things like that now a contra line is going to be connecting All Points of that same elevation like I said and so again just to repeat my original point if you were to walk around on the same contary line you would never be going up or down so if you consider a contary line to be all points of equal elevation and the contary interval to be that amount of elevation you have to climb up or down to hit the next Contra value then it would stand a reason that close Contours so like contour lines that are close together means it's going to be a very steep slope and ones that are farther apart are going to be less sleep steep so for example if I were to draw this like let's say here's I'm going to draw a Hill profile so something like that you know you have a really steep left side and kind of a gentle slope right side I would probably draw this as a topographic map you know something like this you know where the uh the Steep side the lines are closer together let me change my color real quick where the Steep side the lines are closer together and they're farther apart on the gentle slope side now on maps we you should write the elevation of the Contra to kind of you know keep things clear but in many places you know that's not particularly convenient because if you did that then your map would be so covered with numbers that it wouldn't be particularly readable and of course the point of a map is to you know Express information so instead we use something called index Contours and an index Contour is basically every fifth contour line and we mark them by just making them like darker like like a bold face as opposed to normal and we will write the elevation on the index conture line so in this map for example all of these lines are contra lines but in order but we only are going to darken and write in the number for the fifth one so when you're looking at a map if you're trying to figure out the Contra interval then what you would do is you would look at a index contour and look at that value and then you would look at the next closest IND index cont the One X to it and you would say that is going to be a difference of x amount and then you would divide that Difference by five because it's every fifth contour line so like let's say that um cuz you have like 1 2 3 4 keep in mind that this guy right here is the same contour line so let's say I drew another thick contour line right here and and we'll just pretend that purple line there is a contour inter or an index contr and I wrote 800 then I would take what 900 - 800 which is 100 / it by 5 and that would become 20 and that kind of makes sense it would be like 800 for that purple one 820 840 860 880 oh 900 right so this is just kind of defining those what I just said you know that interval is going to be that vertical difference between contour lines and so this is another example of that you know like in this case uh you have uh 1,000 ft at the smaller Contour index contour and 2,000 ft at the bigger one so you have a 1000t elevation difference between index Contours you have five lines you divide it by five that would be 200 ft and you can kind of just spot check that you know 1 12200 1,400 1,600 188 00 oh 2,000 cool now there are a bunch of lines you know a bunch of rules that we have to apply to Contra lines so one is that Contra lines are always going to form in a regular Circle I mean I guess in theory it could form a perfect circle if you were doing something that was a perfect cone or a perfect like sphere but um but for the most part they're going to form in a regular Circle but you might not actually see the fullness of that Circle because in most cases that Circle would continue outside the boundaries of the map so it's very rare that you would actually be able to see an entire circle unless you had a pretty small scale map uh Contra lines also will make a V shape in the Upstream direction of a stream and this is like one of those weird kind of rules but you have to imagine that um if you're looking at like a a a valley like a stream Valley that's kind of cutting into the land in order to kind of match uh elevations from one side of that you know Hill to the other how can I put this so let's look at this kind of like a side view where you have let me change my color where you have like a oh that didn't change at all let me go ahead and erase that real quick erase that too all right so let's go here so you have like a side you here right you got like your little river there you know you can't like just have a contra line that connects these two points on the side because you have that big dip in the middle and so usually you would have to kind of follow it up and I can't draw this three dimensions but you can imagine that you would if you were to follow that you would have to walk kind of slowly going up the hill like like Upstream until the point that the base of the river in the Upstream is going to be the same elevation as the side of the river down here and I can show an example of this so this is a actual topographic map uh with a hillshade applied and so you see the uh redian River you know the blue and so to kind of really demonstrate how these things form these VES I took the contour lines that are as I crossing the river and I made them in red and you can see that they create these vshape and so the V shape like that point of the V is always going to point Upstream so in other words that's going to be upstream and the flow of the river the water is going to flow Downstream like that direction and so you could always spot check this by simply using you know the Contra lines and you know obviously water's always it's going to flow downhill so when and doubt on a map just just check out the contary values but you can use those V's to like really quickly spot it now note that these are drawn pretty sharp and in some cases they can be very sharp but in some cases these V's can look more like a u like the one I'm circling here you know me try to draw it in where it looks a little bit more like that and so we say V but it can be u-shaped it's just a function of the width of the river valley so Contra lines will always increase an elevation along a direction unless it's indicated by hash marks and so you can imagine like a sightedness to this like if you see like a series of Contours let me grab a color here so you have like a series of Contours and then you know that like in one of those directions you're going to be going up slope and then the other you're going to be going down slope now you could specify which direction It Is by putting in numbers like 100 and then like 200 for the second one things like that but if you see hatch marks like these little tick marks that's indicating that that contary value would still be the same that' still be 400 but it's indicating that if you continued walking in that direction you would actually no longer be going upward you'd actually start going downward that would be that depression and I have some examples of this so the bottom picture here shows like a depression where you have like kind of a like a dome with like a um with like a basin inside it so like a like kind of like a volcano with a crater and so you can see that you have um the increasing values until you get to the center and notice how like when you hit the 300 it suddenly is like has those hatch marks which means you're going down slope and It Go eventually you get down low enough or you even get another Contra line because you changed elevation enough to be equal to the cont interval but even then it's still going deeper and so that's going to be hatch marks inside that as well now notice how you have like the 300 here and a 300 here you have that repeated value so you have a 300 you have these repeated Contra lines like that to indicate that there was some sort of continued upward motion but it basically leveled off in such a way as to start descending or whatever so like for example if you had um let me think for a second a scenario like a ridge you know with like a little Dome here you know you might have one contary line here and one contary line here representing the same thing you can see this concept of these repeated values here similarly where um you have the 300 mark here representing by this line and then you got the edge which is represented by that actually in reality it's probably more like that that would be the let me change color real quick so this would be like one and this would be like the other 300 mark and so you know you can see that you still have that little bit of more upward there going uh about but not enough to equal a whole new contour line and I think this picture of a ridge shows it very well where you could see that the hill continues up you know between those two Contour values but you know not enough to equal a whole new Contour point and then it starts going down again and so you have that repeated value um so you can imagine like like I said these have to be completed circles so you can imagine this as like a really big circle let me change my color real quick like a really big circle like this and this being like a really big circle kind of like that and then the sidedness would be you know going uphill in that direction and going uphill in that direction now there are a bunch of other rules of Contra I'm going to go over briefly and so I already mentioned that the closer space of Contra lines are the steeper the surface is but Contra lines can never cross they can never branch they can never change elevation meaning like as they represent All Points of that exact same elevation you can't have it suddenly become a different El elevation they can never skip meaning you can't have like a contra line for elevations 10 20 and then 40 you have to have a 30 elevation in there somewhere um the country lands will always have that upside and downside meaning that um like that directionality you know as I showed in the previous one where you're kind of going up in one uh if you go in One Direction and down if you go in the other direction um and the Contra lines as I said with the rules of V will always point in that Upstream Direction the relief on a map is going to be the difference in elevation between two points and the total relief on a map is going to be the difference in elevation between the highest point and the lowest point on the map so in this case we have you know two points point x and point Y you know connected by a line and the question is like what is going to be the relief between those two points and so you can tell that the index cont line here is 200 let me change my color real quick and the index cont line here is 300 so that means you have 100t difference between index Contours or 100 foot difference between every five Contours so you divided by five that means every contour line is representing a 20ft chain change in elevation and so you say all right well this is going to be um 300 and so you have one contour line and two contour lines so you crossed two 20ft contour lines you went 40 ft now one of the things we're very interested in for you know practical functionality is going to be the gradient of an area in other words we're interested in what the slope of that area is now you guys might remember slope from your algebra classes or your pre-algebra classes where slope is like y overx or in other words it's your rise over run and so the bigger the number the steeper the slope or the steeper the gradient so in this case you know it's asking for the uh gradient between point x and point Y now we already figured out the rise you know it was that 40 ft right so we have to figure out the run now to figure out the run the lower part of that equation you have to measure it now as it turns out um I had that those points set to be exactly equal to that visual scale so it's going to be 3 kilm and so um you would basically say all right um You have 40 m um oh I said feet for this map but uh I meant to assume it was going to be meters just just to keep the system straight so you have a 40 m rise over 3 km run so in other words you have 40 M over 3,000 M now like in math when you have things that are common you can cancel them so you can cancel out the meter here and the meter here because since it's on both top and bottom it's cancelled and you can cancel out one of these 10 values and so so now you have 40 or Sorry 4 over 300 and that would equal 0.13 and that would be your slope or your gradient on the lab you know you're going to have to do a little bit of uh these calculations something called dimensional analysis which is basically trying to manipulate un such that you can cancel them all out so in that last example we kept it straightforward you had a simple uh issue of you know meters to meters but let's say you had a situation where your rise let me grab a color here your rise is 50 ft and your run is going to be let's say 0. 5 miles so you could write that you know 50 ft over 0.5 miles but you can't cancel those units out slope has to be a pure number wow I just realized my 50 ft looks an awful lot like the word soft so what you need to do is you need to find a way to convert feet to miles or miles to feet and so we can set up I like I call them tree equations so like you know just draw that you know boundary line between the two and you can do that so the idea being that you can multiply things so you can put something in here and so this would multiply by this and this would multiply by this now there's something called conversion factors and a conversion factor means something you're taking two values that are equivalent and you can use those to convert to another thing now there's a rule in math that says you can multiply anything by the number one that's a freebie now you have to multiply it on both sides but you can say like you know but you just multiply both sides by the number one you know so it works now here's the thing any any equivalency is going to be equal to one so for example let's say I were to say um 12 in equals 1 foot I mean you guys are aware of this 1 foot is equal to 12 in right well because these are equivalent you can write them as you know like 1T over 12 in or 12 in over 1 foot because they're equivalent and all of this is going to equal one because it's kind of like saying you know like let's say you had 12 over 12 you guys are aware that that would be one you know because you can just cancel out the 12 and all that's left is the one um so whenever you have an equivalency you can set it as a fraction equal to each other like or over on top of each other and you can have either side being top or bottom because in the end it all equals one so all you're doing is multiplying this equation by one so in this case the the conversion is going to be 5,280 ft to a mile and so you want to have a way to cancel the units so you're going to write out you know your 5,280 ft over mile because 5280 ft sorry for my horrible hand rating is equal to 1 mile now you can now that you have that equivalency you can say all right uh I can now cancel out feet because I have a feet on top and bottom and I can cancel out miles cuz I have a mile on top and bottom and so your answer is going to be 50 * 1 as like a quantity divided by the quantity 0.5 time 5,280 and you can just run that into a calculator to solve it I'm not going to do it right now but this is the basis of how you're going to do the unit conversions in the lab next week now there's only two questions like this so don't worry uh I'm not going to be pushing math particularly heavy and I'll be giving examples on how to do it just like this the last thing I want to cover is going to be benchmarks because it's also another important thing you can find on maps and benchmarks are denoted on maps by an X and you usually represent a place where the exact location and elevation is explicitly known like most Maps today are actually generated by satellite and so you know their locations are actually pretty accurate in that regard but historically speaking uh You' begin with a benchmark and then people would use devices like theat alites and other tools to basically triangulate an angle to figure out where the Contra line should be now benchmarks are really useful because they can become like a point of reference um they're usually like when the the USGS is the one that sets benchmarks and so you know the mark does an x on a map but usually where that X where that Benchmark is in real life they usually will create like a circular metal stamp that they literally anchor into the ground itself the picture here is actually a picture of one of these things and like the actual point they're talking will be the dead center of the cross in the middle of the triangle and that's that's that exact point that's known when I was in South Africa uh Excavating ostop aines which is like a homant like a human ancestor um we needed to have measurements accurate to the submillimeter scale because we were also creating all their not just location but their how they were oriented in the ground in three dimensions to create mathematical models to determine if the bones were left there from scavengers or if they were uh pushed in there by like water like flood water and so in order to get that level of measurement uh accuracy uh they actually had a official Benchmark that they utilized and then we more or less we put a device on uh on top of it and then from that device we were able to use lasers to shoot to the exact location to figure out in three dimensions uh exactly where that bone was and not just the bone but like the top of the bone versus the bottom the front versus the back back the left side versus the right side things like that we're able to plot it in three dimensions with an uh to its exact location on Earth with an accuracy greater than or less than 1 mm so submillimeter accuracy that was pretty amazing now for those of you guys who aren't going to be you know in the uh deaths of deepest Africa you know looking for you know million multi-million year old homed fossil bones uh it's actually really useful if you're hiking because you can use it to triangulate yourself it actually takes a little bit of practice for most people to get used to you know being out in nature and looking at a topographic map and figuring out where they are on the map and the benchmarks are a very easy way because you can look around and you look around for what looks like to be the highest peaks like if place like California where you have lots of mountains and so you look around for those highest peaks and you say all right well that's the highest one I see let me look for the highest Benchmark because they often put benchmarks as points of interest you know like City Hall for example or like um or like the tops of tall mountains you know something notable something people are going to notice and so you say you find the tallest mountain peak and then you find the tallest Benchmark you say all right now according to my compass it is you know like I'm facing it and it's I'm facing let's say 25° East you know and then you go look for another mountain peak nearby and you say all right and that's that one and that is the closest tall Peak to the biggest one so let me find that on the map and then I'll a shoot in that coordination you know like now that's 70° East let's say and if you do this with two or three points and you draw their lines um then where all those know lines cross that's going to be where you are on the map and so uh if you guys want like a demonstration of this let me know and I'll I'll put together a demonstration so that's going to be it for the lecture this week uh so as a reminder I would definitely work on the lab next and take some time to study and then you would take the test to last so again uh if you have any questions about the test or about any of the materials please contact me uh by email or by the Q&A message board and I will will have to uh give you a hand also I mean there are a lot of um people who have trouble with some of the aspects of the coming lab you know we're deal with some of these topographic Concepts so you can email me your lab before you finish it or let me rephrase that before you submit it and I'm happy to look it over and give some feedback you know on what you did wrong so that you can correct it and you know get a better grade and understand the material better but you'll have to email me this ideally by Thursday so I have a chance to actually go through it and grade it and deal with it before you know the end of the week so other than that uh this I hope you guys enjoyed this material and um and are studying hard for the test and I will see you guys later bye