hi physical geographers hello again so we've been talking about what's underneath us what's inside the earth and we have gone over the composition of the earth the length of the Earth's history how we break that down and now we're going to look at rocks game rocks so rocks first of all first of all there are many many great Rock enthusiasts in my department at Santa Barbara City College and there are a lot of classes that you can take in the earth science department that go much further into rocks then we're going to go right here there's a lot of geology classes there's environmental geology which goes more into the history of the earth historical geology as well and both of those were both of those classes go like a lot further into rocks also we have these field trips that are normally done in fall and in spring and so fall we go to Sierra Nevada the Eastern Sierra Nevada and in spring we go to Death Valley and in both of those classes those are five-day long field trips field courses you would go much more extensively into the things that we're gonna talk about right now so the things that we've been talking about with the geologic timescale and stuff like that but also with some of the specifics we're going to talk about right now if you're interested in this we have a lot of other great classes that go into all these subjects as well as we have oceanography if you're interested once again and when we talked about thermohaline circulation and we'll talk a little bit more about what's going on inside the ocean but if you're interested in like the geology of the ocean we have an oceanography class we have a lot of classes that you could take after this class that would further your interest if any of this stuff really interest to okay so we have a rock wall dirt Wow Ralph Waldo Emerson quote a foolish consistency is the hobgoblin of little minds Hobgoblin is like a goblin like a demon and adored by little statesmen and philosophers and Divine's do I am that twisted around I'm severely dyslexic I don't know if you've noticed that and some of the things that I say so I might have twisted some of these words wrong because it doesn't make that much sense to me right now but a foolish consistency so sometimes people cut off this part and they just say consistency is the hobgoblin of little minds but it's a foolish consistency something that you do over and over and over again that is a silly thing to do and that's those are the things that destroy us it's basically what ruff Waldo Emerson was saying alright rocks so the cycle of rock change remember the earth is constantly recycling itself and with the carbon cycle with the hydrologic cycle with all of our chemical cycles with our cycle of life you know Mufasa was talking about it and The Lion King with you know the antelope and they die and they become the grass no wait the Lions die they become the grass the antelope eat the grass circle of life so we have our rock recycling and remember we looked at how that starts with the lithosphere being pushed back into the asthenosphere and that that those fear melting into the asthenosphere and then not new magma getting pushed out in a subducting plate boundary or with a divergent plate boundary whenever you have something come from inside the earth out first of all we call that a volcano and second of all its new rock so you have old rock getting pushed into the earth and you have new rock coming out it's sometimes surprises people when I tell them that rocks have different ages that you know the Canadian Shield for example which is part of the country of Canada as some of the oldest rocks in the world billions of years old the Appalachian Mountains that's one of the oldest mountain ranges in the world those rocks are some of the oldest rocks you will find in the entire world sometimes when I tell people that they're like what rocks or rocks they don't have age well yeah they do they were pushed out of the lithosphere as little baby rocks and some of them were pushed out you know 4 billion years ago and some of them were pushed out not quite 4 billion years ago let's say 2 billion years ago 3 billion years ago and some of them are pushed out you know ten million years ago four hundred million years ago so that whole cycle is the rock cycle and so what we want to look at with the rock cycle are the three different types of rock so there's there's lots of subcategories for rocks there's three major kind of umbrella terms for rocks and rocks are classified by how they're formed so how Iraq is formed is how its classified and so we're gonna go over these three major types and then within those types please keep in mind that there are so many different variations so if you remember I said in an earlier lecture what a rock is a rock is two or more minerals so a mineral is a chemical crystalline compound so if we have a chemical that is in its crystal form so a chemical crystalline compound that is a mineral and a mineral is the building block for a rock minerals are inorganic now what gets kind of interesting later is different rock types can have organic material in them in fact organic material can change that rock and and it decomposes and remember organic material has its own chemical compounds so if you imagine that a plant basically rotting and breaking down on a rock those chemicals can react with the chemicals in Iraq and I can change the rock and they can affect the rock and all kinds of different ways so basic basic Iraq is two or more minerals so a mineral and we can we see minerals all around us for example Gold as a mineral pyrite is a mineral graphite what your pencil like the lid of your pencil is made out of graphite that's a mineral a lot of crystals or crystal chemical crystal and compound right that's a crystal is a mineral and so you might have been introduced to minerals through the Scientific earth science route or you might have been introduced to it by like you had a hippie mother who had a bunch of different crystals and we'll talk about their healing power they are chemicals they're chemical compounds hmm you know they how's the history of the universe basically we want to think about it from that kind of makes sense so there are minerals all around us and there's minerals that we use in everyday life like like gold something that's really cool about minerals is that because they're a chemical compound they have a specific shape to them so depending on what that chemical is the way that it bonds is going to sometimes be spherical sometimes be like hexagonal so one of the first ways you identify something that you're looking at you're looking at a rock you're looking at a mineral and you think about what type of mineral this is the one of the first things you do is you look at the shape and does it have like a hexagonal shape repeat it over and over again does it have a cube shape does it have a severe achill shape all that is a clue into what the chemical compound is because different inorganic chemical compounds have their own what's the word I'm looking for form that they take and they replicate over and over again so I thought about like doing this lecture I would have to go to the lab at school and pick up a bunch of rocks and then I realized I have been truly blessed in my life from both picking up rocks all over everywhere and also I've been given a lot of rocks by lots of different students so I just went around the house and collected a bunch of rocks so before I get into our major rock classes this is a mineral so this is sodalite sodalite is like I said a mineral so it's not quite a rock yet right it doesn't have two or more minerals it's just a mineral compounds and in this you can see that even if it's a mineral compound it can have different colors it can have you know different shading to it like there's lighter blue and there's darker blue and I don't think that you can see but when I'm talking about the formation the formation and it would be good if I had like good as opposed to over here where we have a quartz mineral and so if you see what I'm talking about with the formation with how that's like prism basically repeated over and over again so yeah it'd be good if you could see this much clearer I've I've posted a couple different videos on rocks and they will show you like the different inorganic compounds and how they break down in very specific shapes but if you can see like the kind of kind of like you can't really see it it's not good definition basically they're like little prisms repeated over and over again whereas this has a very different chemical compound shape okay I also have this guy here this was cut for me by if anybody knows a key bow he's our he is works in our lab and he found this for me and cut it not pretty so you can see like the chemical compound in the inside all right so we have our minerals those are all minerals and let's talk about our three major rock classes so first first is igneous igneous is your basic rock it is your basic you know Adidas and Lululemon types pumpkin spice latte basic ass rock where you just have magma inside the earth that comes out tell that a volcano by the way from inside the earth it doesn't always come out per volcano but I imagine you have a volcano an igneous rock or magma like liquid molten magma makes its way out from inside the earth and it comes out and it it dries and it hardens that's your igneous rock so igneous rock is your first type of rock well there's many different types of igneous rocks but when we're talking about rock classes we're talking about how they're formed and so the first one is your igneous rock okay then remember the earth is constantly building itself up and it breaks itself back down again we call that weathering so when we build stuff up or when the earth is building up its rocks basically or building up its mountains here comes the rain and here comes the snow and here comes the ice sheets here comes the wind and it just breaks that rock down into smaller and smaller pieces so you have your igneous rock and then it gets broken down into smaller and smaller pieces and eventually it's just like crumbly little pieces and that all sits and it gets compressed and layered more more earth comes on top of it and more and more stuff comes on top of it and eventually that set it's like pushed together and it gets pushed together into sedimentary rock so our igneous rock I had name is rock I forgot to show you our igneous rock right here mmm this is obsidian I showed this to you in a lecture obsidian is volcanic blasting it is like this because it's formed at a very high elevation mmm so it is just your straight-up igneous basic gas rock right now this breaks down over time breaks down into little pieces it gets compressed back together and it forms a sedimentary rock these obviously don't form each other this is limestone this is a rock by the way that I found when I was in graduate school and if you notice sedimentary rocks because they tend to be softer than igneous or than our third rock type do you notice because they're softer they're often really great places to find fossils or fossilized something fossilized that you can see but there's like a leaf that's been fossilized in here so I found this I had to break this apart when I was in grad school I found this in the Sierra all right just anywhere in this era no in the Sierra near the Berkley forestry camp like you know where that is okay so limestone is a type of sedimentary rock it's basically a whole bunch of rock that's been broken down and then and then compressed back together and limestone often forms underwater undersea so it'll have organic material remember I said that minerals are inorganic but then what happens with our sedimentary rock process is because it's it's broken down rock but then other stuff can get in there as well like this whatever this was this leaf that that was compressed inside this sedimentary limestone rock and that organic material that breaks down can mix with the rock and so the chemicals in that organic whatever it is fish shall whatever whatever carbonate whatever it is then mixes in with the pieces of broken-down igneous or broken-down whatever and that can change the chemical composition so that introduction of new chemicals to existing chemicals can change the composition of that rock and can create different types of sedimentary rock and then our third type of rocks that we had our we had magma come out from inside of the earth come out harden igneous rock it gets broken down gets smooshed back together compressed back together into our sedimentary rock all of it comes from minerals over here and then without sedimentary rock it's very deep deep often like when you have plate boundaries together you have a ragini mountain building happening what we have is metamorphic rock so metamorphic rock is your sedimentary rock and you can see like a lines of sediments but those lines of sediment have been pressurized and heated so that they are a lot I know they don't look smooth right there but so there are a lot more a lot more what's the word I'm looking for a lot more like uniform in the rock it would be good if I had a better piece of nice or something like that a metamorphic rock or nice depending on how you pronounce it anyway so our metamorphic rock is basically like like if you ever did clay like if you ever were in school or anything and you'd like made something out of clay and then they took it away and they put it in the kiln and it came back and it was all like smooth so you you took this thing and you like pinched it into a pot and then you painted it and it looked all kind of kind of rough and then they take it away and they put it in the kiln it comes back and it's like all smooth and glassy looking that's like a metamorphic rock it's like take its you take all the sediment you smoosh it together and then you heat it and it gets all like smooth and nice I have different videos that will show you pictures better pictures of metamorphic rocks so don't you worry okay so those are our three classes igneous sedimentary metamorphic great and thinking about what was inside beer at the composition of inside the earth what's gonna come out of inside the earth is somebody knocking on my door so what's inside the earth it would make sense that what's inside the earth when it comes out in form of magma all of the different the composition of inside of the earth is gonna come out as well so oxygen silicon remember we said that there were silicates inside the earth we said there was iron inside of the earth all of these parts of the crust are parts of the asthenosphere essentially gonna come out and they're going to affect what the igneous rock is if that makes sense so what kind of igneous rock you might have so basically the minerals that's the crystalline chemical compounds that come from the chemicals that are inside the earth the chemical composition of the inside of the earth when it comes out and hardens its igneous rock but those minerals might be different so that's why we have different types of igneous rock okay igneous rock is straight-up magma there we go there's magma coming out of the earth and then we have rock that breaks down and it gets pushed back together squished back together and what we call sedimentary rock or second rock type and biomass can be part of that because like I said you have little pieces of rock that they get mixed in with different organic material that organic material has its own chemical composition they mix together they might have a reaction that forms a completely different type of sedimentary rock so you might have new minerals introduced they might they might react with the chemicals that are part of the organic material you get it we can have intrusive igneous rocks and we're gonna have extrusive igneous rocks so just like we talked about exogenic and endo genic processes processes inside the earth and processes outside of the earth some igneous rock is formed like this like if we were on the Big Island of Hawaii right now there is a volcanic eruption that is happening currently right now on the Big Island of Hawaii remember it's over a hot spot so it's not like a Vesuvius volcanic eruption it's more like a gradual volcanic eruption but that's forming new igneous rock right now right now as we speak but there's also rock igneous rock that is intrusive that is inside the earth so you have two tongs you have you have magma that makes its way out of the asthenosphere but doesn't make its way all the way out to where we are so you have magma that might like make its way out into already formed rock which is how you can come across like if you're ever hiking and you're on like Sam stone or some sort of some sort of you know uniform rock whatever it is and then you might come across like a strip of totally different rock like you're walking along Sam stone and then suddenly there's just like a strip of granite that's an intrusive dike that's not a slur that's what it's called it's an intrusive dike so an intrusive dike I'll show you on a slide later is when you have an intrusive Rock you have intrusive magma so you haven't already solidified rock and then you have more magma come in to that solidified Rock and now you have an intrusive igneous rock a rock that basically formed inside a new rock that formed inside an already established rock so our sedimentary rock is going to be layered in strata because basically its material and more material and then more material that all gets compressed on top so it can you can have real variations of the chemicals and the minerals in your sedimentary rock major classes of sedimentary rocks that remember sedimentary rock is we've got our three different formations around igneous sedimentary and metamorphic inside each one of those there's many different variations of them so sedimentary rock can be further broken down to clastic that's rock and mineral fragments to chemically precipitated so if you imagine there's a lot of different chemical processes that are happening when chemicals meet each other but then also if you take something like sea water for example ocean water has salt in it so when it heats up it it gets bigger salts you know it's like an air mass it gets larger when it's warmer and and more dense when it's colder and that can have that can do some mechanical weathering but then also the composition of salts can chemically change or alter a rock so you can have something called chemical precipitation so chemical precipitation and it's um and it's kind of short form is when you have two liquids two soluble materials that come together and form a solid if that makes sense but I don't want to go too into this because it's not necessary for the depth of this class but you have essentially chemical reactions where you have two solvent that come to solvent chemicals that come together and and form a solid if that makes sense and that's all it is are sedimentary rock and then organic material or sorry organic sedimentary rock is formed from organic material so if you imagine what kind of organic material would create sedimentary rock and that's when you look at something that might be fossilized or the organic compounds the chemical compounds that break down from organic material but then gets what's it called compressed together and are plastic sediment there is remember back here plastic rock and mineral fragments or clastic sediments and stone well I just mentioned sandstone shale chemical precipitations chalk next to clips for example what we're going to see from coming from from ocean water salty water and then metamorphic rock that's our rock that is pressurized heated usually next to a fault or where there's there's a whole lot of like plate boundaries or next to a fault or there's something like really really creating pressure and one thing to note is that different colors can tell you about what the minerals are in the rock so felsic rock for example is light-colored it's less dense it's lighter mafic rock is darker colored ultramafic rock is very heavy and dark colored the way that remember being a scientist is is not knowing anything in particular it is asking questions so asking questions and knowing certain rules and certain ideas and remember taking like this mixed bag you don't know what's inside it but you have certain rules and certain measures you know you can apply and taking out the puzzle pieces in that mixed bag and using different ideas that you have different information you have to kind of fit those puzzle pieces together and create a story so when we look at a rock we don't necessarily know what this rock is or this is an ax rock this is a mineral but we don't necessarily know what this is so we use different identifiers we know that chemical compounds form different types of structures so if we know that a certain structure is going to result from a chemical compound we can look at that structure and be like Oh cubes we know that different colors are going to reflect mineral contents so if we have a lighter Rock if we have a darker Rock it will tell us what mineral content the mineral component might be in that rock we also what are some other ways Oh other ways would be color color is gonna tell us a whole lot about Rock Sheen is gonna tell us a whole lot about rocky but shiny if it's not shiny and you can taste it so remember rocks are made of different minerals and a lot of people who study rocks or study the surface of the earth or the Earth's history will just lick a rock to try to figure out what it is because you know if you have chemically precipitated Rock like chopped you probably not gonna lick chalk but don't think about it if you have something that that that one of the main minerals is salts it's gonna taste pretty salty and so by looking at that can tell you a lot more than just looking at it and trying to break it apart so we lick things we look at their shape we look at their color we look at how shiny they are all of those are different ways that we put together on what kind of rocks this it's gold what is this this is Yosemite so this is Half Dome in Yosemite and Half Dome and Yosemite is a batholith so batholith I have it written on the next page don't worry about the lip is a type of igneous formation so remember we're talking about igneous rocks it's a type of igneous formation it's a large intrusive igneous rock it's formed deep in the Earth's surface so the Sierra Nevada are young mountains and remember you can tell that for one there's a lot of different ways that you can tell that before one is they're really really steep and they're majestic and they're tall and if they had been around for as long as the Appalachians they'd be a lot shorter and then have a lot like smoother kind of edges to them because that's what the earth does builds everything up and then it breaks it back down again so when we look at let's say the Sierra Nevada we know that the mountains are pretty young the mountains are maybe ten million years old maybe five million years old but the rocks are older the rocks are 350 million four hundred million years old and what happened essentially as we had this intrusive igneous rock that was created or formed I should say I always knew the Lord created created and I should use the word formed more but we have this igneous intrusion granite rock that was formed underneath the earth and then eventually we had uplift so we have all these rocks forming underneath the earth earth these intrusive rocks and then eventually the Farallon plate subducts under north america and it pushes up those rocks those rocks that had already formed inside the earth 400 million years ago 350 million years ago ten million years ago get pushed up so that's how you can have a mountain range that has a different age from the rocks that make up that mountain range anyway so a baffle is is I'm gonna show you on the next slide but you know somebody has a good example of a baffle lift in order to be a baffle if it means that you are an igneous intrusion formed inside the earth and then this was uplifted you have to have an exposed area of the Earth's surface it should it has to be about a hundred square kilometres right 100 square kilometers 100 kilometers squared how do I say that it has to be we have to be able to see about a hundred square kilometers in order for it to be considered a pacifist this here was formed in the Nevada orogeny so orogeny means Mountain building a raagh means mountain right orogeny is mountain building and something else I want to tell you guys you all is different types of rocks that form so before I get into batholith more into battle with in just a second one thing I forgot to tell you is if we have metamorphic rocks that are basically sedimentary rocks that have been heated and pressurized inside the earth for a long time I wanted to tell you different rocks that form into different rocks so granite becomes shoot nice that's right so granite becomes nice or nice depending on how to you so granite when it is heated and pressurized becomes nice one of our metamorphic rocks limestone so limestone when it's heated and pressurized becomes marble and let's the other one I wanted to tell you all I forgot there's another one that's cool but yeah just to give you an idea those are two rocks that you might know granite you might know you know cuz like granite countertops or something like that you might have heard of limestone you might have heard of marble so marble is limestone limestone is a sedimentary version and then marble is the metamorphic version okay last thing we have our baffle is so here a batholith is a collection of plutons so in order to be about the lift you have to be a coupe a batholith is a collection of plutons futons are again igneous rocks intrusive igneous rocks that are formed our igneous rocks are our Sierra Nevada are comprised mostly there's a logic from rocks in the Sierra Nevada but there's a lot of granite and the Sierra Nevada in fact that is what this is right here so granite is an igneous rock and you can often see granite on it you can often see that granite has a lot of like pieces kind of significant sort of chunks to it if that makes sense so there's so it often looks like you can see little little flecks that's one of the reasons that it might be used for kitchen countertops or something like that because it has like a very interesting sort of pretty natural design where you'll see like little flecks of like white little flecks of black little flecks of like kind of different colors some of them might be shiny and that has to do with how slowly granite forms so bran it is so granite in particular is a very slow forming igneous rock and that's why we can like see almost the different pieces and it's slow formation you can like see the different pieces come to they become more present so our pluton igneous rock intrusive igneous rock when you have a collection of plutons we call that a baffle off' and that baffle if then contributes to all of these different new intrusive pieces of an already established rock or an already established mountain an already established series of mountains volcanic arc so let's say here we have all of our layers of sediment we have our already established rock or already established mountain and now we have this new intrusive igneous rock with soot on then we have a collection of plutons that we call a batholith and that baffle if that collection of pluton some magma might make its way up like right in the middle of already layered sediment so you have sediment that has already been layered over millions of years you have igneous rock that might have been created ten million years ago and now you have this new pluton that comes up and when you have just a little like kind of fissure like right here we call that a dike so that that and it's called an intrusive type because it intrudes upon these already established layers of strata okay so sometimes that dike makes its way up and now you have these layers of strata and magma gets like wedged right in the middle so instead of being like instead of splitting the strata into which is what a dike does it comes along and it gets like kind of wedged in between two layers of strata so when you have new magma that comes in between these two layers of strata we call it a sill and then when not kind of like when that sill gets more and more material in it more and more magma in it and starts to create like a little lump which can look like a hill up here what's called a lack of lift so laccolith dike so batholith collection of plutons and then Xena lifts as a rock that might have been surrounded by that new intrusive Teuton or intrusive batholith okay that's it I have several videos on the rock cycle that should help you with this that show different pictures and has different people talking about it and that's it next time we will talk about volcanoes and earthquakes