we're going to be talking about the planets one by one which one we're going to start with we're gonna start with earth it makes sense to start with mercury but we're gonna start with earth because we live there and also I'm not gonna say everything about Earth take a geology class if you'd like to learn more about it so let me just pop this up right here and mainly I want to talk about some things about Earth that will help us understand some of the other planets so here's the earth I'd like to look inside I'm gonna go a little bit quick when it comes to earth now in this picture ignore these wiggly lines right here just ignore this I just want to show the layers inside of the earth okay so let me pop over here get this clear [Music] oops just need to change that text size back there we go okay so Earth's interior is divided into four basic layers okay and let me just make sure I'm still not getting any of this okay all right four basic layers and I know most of you have probably already learned about these layers so this should be a review for most of you but if you haven't I'll give you everything you need for this course okay so does any know what we call the very very middle of the of the earth it's pretty simple what do we call that middle part yeah we got it we got it so these two parts together are called the core of the planet but we're going to divide them up into two separate layers for the purposes of this class so what I'm going to do is I'm going to pop over to my text screen and the way this is going to work is that the number one at the top is what we're walking around on and four is the very center of the planet so what we call these two core layers in the end there we go do this the very very middle is called the solid iron inner core so mean but any guesses as to what it's mainly made out of and any guesses they're a good job I'm not gonna look it's mostly made out of iron good job guys but it's not just made out of iron even though we call it the solid iron inner core it has a few other types of metal mixed in it's just mostly iron and other metals like nickel and a few other things but yeah so it's solid it's metal it's the inner core all right when you go out and that's again that's going to be this area right in the center right here that's the solid iron inner core now this part is called so this outer grey part here is called the liquid iron outer core so let me type that in over here so liquid iron outer core and it's basically the same as the solid iron inner core except well the outer core is solid and the inner like the inner core is solid and the outer core is liquid okay so but they're made of the same thing so iron and nickel and it's pretty much all metal in there it's not a lot of what we call rock okay and I'll explain what I mean about that when I get to the next layer okay so solid iron inner core liquid iron outer core does anybody happen to know what this next area is right around here this this big red area around the core what's that called so this one you probably have learned the name of the mantle yes oh so there's a question right here about how the inner core can be solid and the core can be liquid that is let me let me come back to that in in just a second as soon as I'm done with all of the different layers I'll answer that question but I will be getting to that okay so yes the the next layer right there the one that's colored red is called the mantle so let me get that on here so the mantle make sure we spell it right it's the mantle okay so the mantle now notice here in our picture where's my mouse okay in our picture they've colored the solid iron inner core and the liquid iron and outer core are both the same color and then they color the mantle something different now what they're trying to show there is that the mantle is made out of a different type of material it's still got a lot of iron in it but it's also got of like a lot of rocky material mixed in specifically what we call the majority of the rocky material on our earth and then the other terrestrial planets actually is called silicates now silicates are essentially types of rocks that are primarily made of silicon and oxygen and I'll I'll type that up in case you don't know how to spell it one moment let me pop that over so mantle would have metal and silicates maybe I'll put it up in a slash so that isn't metal and silicates of silicates whenever you see silicates just think rock a good example of a silicate is granite it's not gonna be in the form of granite in the mantle that's something we have up here on the surface but it granite and this stuff and sand for example is all made of roughly the same stuff a lot of silicon and oxygen in those rocks so the mantle we start having that mixed in and then finally does anybody know what that last layer is in the picture it's very very thin way up on the outer outer edge just outside of the red area what is that part we're walking around on it right now yes that is the crust so the final layer is the crust and let me pop that over here the rust so there that's the the four layers that are gonna have for the earth the crust is very thin here's my question do we have any silicates up here on the crust yes all right like I said granite sand all of that stuff that's made of silicates okay so when you again when you think of silicates you're thinking regular types of rocks do we have any iron up here on the crust or is it all in those lower layers is there any iron here on the crust yes yes okay obviously there is the iron is in we know there's iron in the crust because you know what iron is and you have things made out of iron like skillets and and all kinds of things so in general what happens to the amount of silicates as you come towards the crust you get more and more and more silicates as you go towards the crust and as you go towards the core you get more and more and more metal more and more iron for example and the reason for that is if you remember when the planets formed they first started as liquids and what's heavier iron or regular rocks like silicates like pure iron or regular rocks like silicates which one's heavier yes it's the iron so in that state when the earth was still liquid what happened to all the heavy iron well it started to sink towards the center of the planet okay and then the lighter rocky material started to rise towards the top and the reason we have these layers with varying amounts as you go towards the top is that while that the heavy stuff was sinking and the light stuff was rising the Earth's solidified or at least mostly solidified locking the material wherever it is excuse me so for example the material in the crust is not gonna sink all the way down like the eye that we still have in the crust is not gonna sink all the way down to the core because the crust is mostly solid all right let me see if we have any questions there okay now and I need to go back and answer that question about the little tricky part of all this and that is if we look at the core here this parts solid this parts liquid and that's weird because we said that the earth gets hotter and hotter and hotter and hotter as you get towards the center so this solid iron is hotter than this liquid iron that's not how things normally work like if you had some cheese and you wanted to make nachos you wouldn't make it colder to melt it you'd make it hotter right so this seems to be weird does anybody know what's keeping the very middle of the planets solid when let me put it this way it should melt but it does not okay the core the inner core of the planet should melt but it does not so the answer there is pressure so if we go towards the center of the planet the deeper you go the more weight there is above you and that's pressing down on you and when something melts what's really happening at the molecular level is it when something solid its molecules are sort of they're not 100% locked in place but they're pretty locked in place and then when when that material gets really really hot those those molecules will jiggle a bunch and eventually break apart and that is the formation of it becoming a liquid so if you can hold them tight you keep them from separating and so something that's hot enough to melt under normal situations like up on the surface of the planet won't melt if it's under a lot of pressure so basically the solid iron air core is is under enough pressure for it to keep from melting but the liquid iron outer core doesn't have enough pressure to keep from melting so it melts so it's a little bit of a weird situation there hopefully that answers the question now what is what am I talking about all of this for well we said the solid solid inner core is solid the liquid iron outer core is liquid the mantle mantle is a little bit iffy it's mostly solid but that solid can flow a little bit very very very slowly sometimes called plastic and the very very very top of the mantle because it's under less pressure than the rest is the most liquid of part of the mantle so the very top of the mantle actually has its own name and it's called the asthenosphere the asthenosphere so if you go over here to my text I'm gonna type that out so the very top of the mantle where it is the most liquid is called the asthenosphere asthenosphere it's not a separate layer it's part of the mantle it's just the top part so basically our and then if you go up to the crust the crust is also mostly solid so our planet actually has two different places inside that are liquid we have the liquid iron outer core and the very top of the mantle that's the asthenosphere okay so here's my next question which one of those two probably drives our geological activity like our volcanoes is the lava that comes out of volcanoes coming from the liquid iron outer core or is it coming from the top of the mantle the asthenosphere which one of those areas sins the law of out and yeah I know it's called magma inside but this isn't a geology class I'm just gonna say lava right it's the asthenosphere and that makes a lot of sense because the asthenosphere is closer to the crust so if any of them is going to send it's going to affect the crust it's gonna be the one right under the crust so the asthenosphere gives us our geological activity but our magnetic field comes from the liquid iron outer core because remember in order for a magnetic field to form you need to be a liquid conductor and liquid iron conducts electricity but liquid silicates liquid rock generally doesn't do that very well so the mantle being much more rocky can't really conduct a magnetic can't conduct electricity so it can't make a magnetic field whereas the liquid iron outer core does so we need both of those to account for the things that happen on earth okay everybody with me okay so here we go here we go what I'm gonna do is we're going to talk about geological activity real quick and then we're gonna talk about the magnetic field a little bit more not much just I want to show one effect of the magnetic field so let's talk about some geological activity I said this was things like earthquakes and volcanoes and clearly we have those but there's one type of geological activity that we have on earth that no other planet has and you probably have heard of it it's called plate tectonics okay plate tectonics who hears heard of a plate tectonics you guys learned about that in school at some point if you have what part of our planet is the plates which of these layers that we were talking about here which one is made out of plates yes plate tectonics can cause earthquakes it's it's not the only thing that causes earthquakes but it's the primary driver of earthquakes on earth okay but yeah it's the crust so you may have seen a picture that looks something like this let me bring up my again so this is a picture of the entire surface of the earth this is the whole crust of the earth here and what they're trying to show on these little yellow lines is that our crust is broken into pieces like big chunks and we call those chunks plates so for example us here in North America our plate is this entire region right here so if let me do there we go so this is one edge of our plate and then it swoops around and then it goes up the middle of the Atlantic Ocean and it kind of goes off the page right here but yeah so the plates are not just the continents there the entire crust so for example again we're the North American plate over here we have the Pacific plate where most of the Pacific Ocean is on then we have the South American plate now we are not entirely sure how these plates formed because our crust in general is actually even though it looks really thin compared to the other layers it's actually pretty thick it's miles deep and it's a very hard to break so we are not sure why it is broken but it is broken okay and what this said what this does is these plates actually move around over time now is it very fast no we actually can track it with GPS these days and we see that they move a few inches every year but they're not all moving the same direction so some plates are moving east some remote north they show the direction of some of those motions with some of these arrows but they're not showing all of them but yeah these plates are moving around now what's making them move around oh yes somebody asked about fault lines faultline these yellow lines right here fault lines are along the edges of the plates yes yes so you probably have heard of the fault lines along the coast of California that's because California is on the edge of plates okay good question there now um what was they say oh yes um so these plates are moving around now why are they moving around well wind is not gonna do it so there's nothing happening above the crust that's getting these things to move around why are these solid plates able to move around well remember what's right underneath the crust what's right underneath the crust what layer when layer we got no it's the mantle but what that what part of the mantle is right underneath the crust it's the asthenosphere okay the asthenosphere which has magma in it so the the molten asthenosphere is right underneath the crust and so essentially because of motion in that magma the plates are able to slide around on that molten material okay and we get a lot of things happening because of this for example the Atlantic Ocean is a plate place where plates are moving apart and what that does is it makes the Atlantic Ocean grow over time okay but in other places much more important for us when we talk about other planets some of the plates are running into each other for example the Pacific plate right here is sorry right here let's do this the Pacific plate right here is ramming into the North American plate right here right along the coast of California and does anybody know what that causes all along the coast of California this one should be pretty pretty easy what are we getting all along the coast of California there we go we get some people saying it we got earthquakes happening so one of the things that can happen where plates are running together is earthquakes so what are some other places where in the world they get a lot of earthquakes there's a lot of places to get them all the time just think about them so another place that has a lot of earthquakes is right here along the coast of South America and if you look right here look at the motion what are these two plates doing right here they're coming together right here you probably have heard of a lot of earthquakes in Japan if we look over here Japan is right on the edge of some plates they haven't drawn the edge of all the plates there's another plate edge right here in the Himalayas and there's a lot of earthquakes there too so a lot of earthquakes there additionally it's a little bit easier for volcanoes to spring up on the edges of plates so because the crust is a little bit weaker right there and a lot of other more complicated things and that take a geology class but there didn't I know what we call the ring of volcanoes that's all around the edge of the Pacific Ocean it's called the Ring of Fire and basically all along this yellow line right here around the Pacific Ocean you get lots of volcanoes and so it rings all the way around the Pacific because the Pacific Ocean is all on a plate so yeah this makes it so that we are more geologically active than any other terrestrial planet and this plate tectonics actually increases our level of geological activity beyond what we would have had if our crust wasn't broken and moving like this so I want you to point I want to point out some one last thing about that that's very very important if we look over here if we look right here all along the places we said that there were earthquakes check out right here check out right here check out the Himalayas check out Japan a little bit harder to see here what do we have in all of those regions so notice all those regions are colored kind of on this this map and this is an elevation map that brownish red is red color is saying that those places are high so what what are we getting along those fault lines where plates are coming together yeah mountain ranges high evolution are high elevation mountain ranges so essentially what's happening is whenever plates ram into each other specifically if you have two plates where at least on those plates where at least one of the edges has land like continent on it it doesn't happen nearly as much if you've got two ocean plates coming together but if you have two plates coming together it's just like when any two things ram into each other like imagine two cars coming together when two cars Ram each other head-on do they keep their shape no what happens is they they wrinkle all up so like two cars come together like your cars get totaled yeah you get you get all wrinkled up the same thing is happening to these plates everywhere the plates are ramming into each other is a head-on collision of plates and so what's happening is those plates are buckling up like the front of a car that's wrecking so mountain ranges are the wreckage on the plates and so we can actually track and figure out where old plate edges are by looking for mountain ranges but here's something important if our planet is the only planet that has widespread plate tectonics what does that mean we do not expect to find on the surface of the other three terrestrial planets see if you can pay the piece that one together okay so it looks like you guys are basically getting this so you can still have individual volcanoes and mountains those can actually melt their volcanoes can melt their way through pretty much anywhere on the planet even at it's just easier to have volcanoes on the edges but mountain ranges so like a bunch of mountains in a line like that are not gonna form without plate tectonics so in general on the other planets we do get sometimes have mountains they just tend to be individual mountains or maybe a group of volcanoes that all formed in the same spot but it's just not a range okay everybody good okay all right all right here we go now we're almost done with Earth I just got a little bit more I want to say let me skip a few slides ahead I mentioned the magnetic field and somebody actually brought this up earlier with a question our magnetic field protects us from the Sun so if we look in this picture over here you can see the basic pumpkin shape of the magnetic field coming out of the North Pole and going into the South Pole that I was talking about earlier okay it's a little bit distorted here on this side and I'll explain why that is but basically what this does for us is it protects us from the solar wind remember we talked about the solar wind when we were talking about comets and we also when if you read the notes on how the form the the solar system formed it gets mentioned in there also but yeah the Sun is constantly blowing a stream of charged particles out in all directions now luckily for us remember our magnetic field forms because of electricity so elec electronic fields are related specifically our magnetic field came from electric charge and then things that are electric charged follow magnetic fields so the Sun is trying to blast us with this stream of solar wind is trying to get to just hit the earth here but because of our magnetic field when that stream of particles hits the the magnetic field it tends to turn and try to follow it and luckily it for us because it moves so quickly most of it ends up sliding around the outer edges so our magnetic field essentially kind of works like an umbrella and this over here the place where it's distorted is actually where the charged particles from the solar wind that are that are flying past the planet are actually distorting our magnetic field and trying to drag it along with it they really like magnetic fields okay so we're protected from the solar wind in that way but where is our magnetic field gonna be weakest where's it gonna be the weakest there's two places on our planet which don't protect from the solar wind nearly as well see if you can figure out where they are yeah there we go it's the poles it's the poles you can see where the magnetic field dips in there they even are showing some of the solar wind kind of sneaking its way into those poles but luckily for us that want the solar wind doesn't have a direct hit path at the poles because our poles are perpendicular meaning it almost it they're not exactly perpendicular because of the tilt of the earth and but the poles aren't pointing straight at the Sun is what I'm trying to say so we're not getting a direct dose of solar wind right down that that pole and what happens is that the charged particles lose a lot of their energy when they have to turn around this area right here and so by the time they hit the earth they don't even really have enough energy to get through the atmosphere okay and so all the end up doing is they hit the atmosphere give their energy to the gas in the atmosphere and does anybody know what we see in that situation ah if somebody actually already mentioned it this is called an Aurora when the solar wind makes contact with our atmosphere it causes the atmosphere to light up in a pattern that sort of looks like this and it's not always it's not always this exact color on earth it's usually a mixture of green and red and that's because the Earth's atmosphere is primarily made of oxygen and nitrogen one of those lights up green and one of those lights up red when it gets energized by the solar wind like this so other planets that have atmospheres made out of different stuff could have Aurora's but it's not going to be the same color for example on Jupiter Jupiter has Aurora's and they are more of a bright blue color and oh and if you don't know how to spell Aurora it's it's right here au r o ra so an Aurora is gonna be found at the polls so that's why we can't see Aurora's in Florida because we're just not close enough to the polls to get that effect oh and if you're if you're wondering if you've ever heard the term aurora borealis aurora borealis is what we call the aurora that happens near the North Pole and the one down at the South Pole is called aurora australis because one place you can see it from is Australia but you can see them from anywhere close enough to the South Pole don't worry about borealis or Australis as long as you know Aurora you're good