 Well, it's just about time to run. We have been through a lot together. We've been to some of the most beautiful places in the world. We've talked to some of the most interesting people. We've seen wonderful things. You have a chance to learn how the world works in a really fundamental way. We have crossed over a whole lot of the earth sciences in a very short period of time, and now you're going to go off and take that knowledge, and I hope you're going to go on a road trip. You're going to go see something really tremendous. Go to some of these national parks, learn some of the things in real life that you've seen in our slides, and have a great time. I hope you know that Trader and I are really excited about this subject, that we really believe it matters to you. You don't have these little things that, you know, occasionally there's a little grading, occasionally there's a little team, and so we thought it would be useful to walk through a little bit of a review with you. And so I'm going to start you off on some reviewing things here. This is actually a picture that I took in Alaska of some stuff that was scraped off of the down going subductions on slab, and then there's been landslides and there's been glacier erosion, and there's a whole bunch of beautiful things in this national park shown right here up at Glacier Bay. And to make it easier, I hope, I'm going to try to sing you the course. I'm going to walk us through a couple of verses. I said in the first half of the course what Schroeder taught and a little of what I did. Then we'll stop and we'll write some overheads. And then I'll sing you through the rest of the course. So it's not like I'm turning a little more than we did in the course. What a song we can do the whole course in a little extra. And then we'll stop and write some more things, and then I will bid you a pleasant good life and hope that we'll meet somewhere in a park down the road. And so we'll walk you through a little singing here. And so I'm going to try desperately to sing this somewhere vaguely in tune and see what we come up with. The chorus is an opinion. I'm giving you science in here, but when we get down to the chorus, this is an opinion, you don't have to parent back what I say, but I really believe this. So let's see if we can get somewhere interesting here and see what we can do. I'm giving you science in here, but when we get down to the chorus, this is an opinion, you don't have to parent back what I say, but I really believe this. So let's see if we can get somewhere interesting here. And so I'm going to try desperately to sing this somewhere vaguely in tune and see what we can do. So let's see if we can get somewhere interesting here. And so I'm giving you science in here, but when we get down to the chorus, this is an opinion, you don't have to parent back what I say, but I really believe this. So let's see if we can get somewhere interesting here. And so I'm giving you science in here, but when we get down to the chorus, this is an opinion, you don't have to parent back what I say, but I really believe this. So let's see if we can get somewhere interesting here. And so I'm giving you science in here, but when we get down to the chorus, this is an opinion, you don't have to parent back what I say, but I really believe this. So let's see if we can get somewhere interesting here. And so I'm giving you science in here, but when we get down to the chorus, this is an opinion, you don't have to parent back what I say, but I really believe this. So let's see if we can get somewhere interesting here. And so I'm giving you science in here, but when we get down to the chorus, this is an opinion, okay, so there is about half of the chorus in a very short order, and I'm going to try to flip over just a little bit, and we're going to change speakers on you. You have this wonderful AV setup from really good work, and I think we actually will have made this work. And so now let's see if we can do a little bit of review on things that we've looked at. So we'll switch over here, and we're going to be more familiar. Okay, in the chorus, we started sort of back at the beginning. We said, hey, the universe is older than the Earth is. There were some stars, they blew up. They made very interesting things that floated around in a solar nebula, and eventually it all fell together to make the Earth. And so the Earth formed by stuff falling down under gravity. Stuff fell together. This is really technical. I hope you're with me on this. So stuff fell in for the Earth, and when stuff falls together it gets hot, and there was a lot of radioactivity then. And so we had stuff got hot. And so it heated, and the heat mostly from radioactivity, and the heat led to melting, and the melting led to separation into layers. And this one, you sort of remember, if you've ever driven in the north, and you've driven in the winter, and you drive along and get snow and ice on the bottom of the car, and there's rocks in it, and there's salt in it, and there's little dense coral parts in it, and all that kind of stuff, and you drive in the garage, and it melts, it separates. And so in the same way as the planet melted, it separated into layers of dense core to the middle, a little scuzz that floats on top that is the crust in the atmosphere, and a big thick mantle in between. Okay, so we looked at the different layers, and we looked at the radioactivity, and that is still making it hot, and so there's some heat left from a long ago, but mostly there's radioactivity, which makes it hot. And when you make things hot, whether it be the Hershey bar in your pocket or whether it be the center of the earth, they get soft. And so it makes it hot, and the hot makes it soft, and the soft makes it flow. And in fact, down there, stirring in the mantle, the currents flow, they have convection cells down there. And so we have convection down deep in the mantle moving things around. And you may remember that convection sort of looks like this, and on top of that there are big slabs of rock, and on top of that is your house, big house. Okay, so you can possibly remember going over some of this a little bit back. And so we have soft flowing down below, and we have hard breaking up above. And we live on the hard breaking, so we sort of talk about the hard breaking most of the time rather than the soft flowing, because we're sort of us and cook most of the time. So when we looked at this, we found that the upper layers of the planet are broken into a few big chunks, which we call plates. And so there are plates that are rafting around on the convection cells. And you know that if you're on a raft going down the river, if you sit in the middle of the raft, it's sort of boring. And if you hang your fingers over the edge, they'll get nibbled on by the catfish, or they'll get crushed when you run into another raft. The action is at the edge. That's the bumpering sort of happens. And so we looked at the interactions of these plates at their edges. And we said there's really sort of three things they can do. They can slide past each other. They're not coming towards or away. They're just sliding past. And we said in a slide past sort of world, you don't get a lot of mountain building, but you do get earthquakes. And so slide past, you can get quakes. And the example that we talked about aren't many national parks devoted to sliding past. And the reason is it doesn't make big, pretty valleys and it doesn't make big, pretty mountains. But the San Andreas fault that tries to knock down L.A. in San Francisco is a good slide past boundary. And so we talked about the San Andreas as the big fault that is a slide past in the West. And it serves as a good example of this. We get national parks at the other two kinds of boundaries. We looked at pull apart boundaries. In fact, we started way back when at a pull apart boundary. That was Death Valley. And Death Valley, remember, is sort of unzipping. California moving away from the mainland a little bit. Not as fast as they think they are, but nonetheless they are. And south from there, we went out into the Gulf of California, which was unzipping, and out into the great mid-ocean ridges that are unzipping. And so what we found at pull apart boundaries is if you start one in a continent, you get pull apart faults, you get earthquakes, you get Death Valley. And if it keeps unzipping, the rift valleys of Death Valley will make seafloor. And so eventually you get seafloor. And we saw that a little bit of melted rock leaks up the crack. You get a little basalt coming up the cracks. And so you get basaltic volcanoes that are leaking up from the mantle and they cool and harden and make the seafloor. And then there's seafloor spreading stuff. It's moving away from the center of this as things leak up. And so you may possibly remember diagrams that sort of look something like this, with this going this way and this going this way, and a red volcano. Let's make a red volcano. A red volcano coming up like this from below and the stuff freezing. And so there are very interesting boundaries. There's fun stuff that happens at them and they do give us some national parts. The biggest deal for getting national parts turns out to be at the push-together boundaries. And so we have push-together boundaries. And this one, there's a couple types. And you will possibly recall that when old seafloor gets really cold, it gets dense enough to sink back into the mantle. And so old, cold seafloor will sink into the mantle. And when that happens, you get what we call a subduction zone. So this is at a subduction zone. And in the subduction zone, we had all kinds of national parts. We had stuff scrape off the down-going slab. And when you scrape stuff off, you get the hills of San Francisco, you get the hills that the redwoods are growing on, you get Olympic National Park. So there's a huge number of fun things that happen out there. So we have scrape off and scrape off gives us Olympic. And that was a really fun national park to visit. I hope you remember that one. It was a pretty one. And we also have a little bit of sediment and water go down. So a little of the sediment doesn't get scraped off. It goes down. Sediments goes all the way down and water goes down. And what we found is that when you put water in the system, water lowers the melting point. So you're taking this slab down. There's friction. There's heating. And you do some melting down there. And that melting is a very special melt that has water in it and it has a lot of silica in it. And so this makes melt. And the melt comes up, but the melt has water in it. And when the water gets up to the surface, either it sort of bubbles off nicely and you get really slow gooey lava flows, or it bubbles off not nicely and you get really fast into the stratosphere and change the climate and kill everybody around. And you make stratovolcanoes and you make all sorts of interesting things. So this gave us in the site as the rock. And this was one with more silica than basalt. You sweated the in the site out of the basalt, essentially. And you get stratovolcanoes. And the stratovolcanoes you will remember are things such as Mount St. Helens or Crater Lake. And Crater Lake is a big hole. That mountain is spread out across the Badlands and out across Yellowstone and spread around the world. And so we had Mount St. Helens and we had Crater Lake and other sorts of interesting things that were sitting there like that. We also noted that there are earthquakes at subduction zones. Most of them are the same as other kinds of earthquakes. It sticks and it slips and it sticks and it slips. And there may be some really deep ones that squeeze the down-going rock. It just sort of collapses or implodes. And so we saw there are earthquakes and at subduction zones the earthquakes include normal or stick-slip sort of motion, elastic rebound. We talked about there where they get stuck, they're like a rubber band, and then boom, they let go. And then there were special implosion earthquakes as the stuff was going way down the great depth and it could squeeze and squeeze and squeeze and finally it just caves in. So we'll call those implosion quakes. So there is all kinds of activity going on at subduction zones. There are trenches offshore and there's volcanic arcs. And so we have trenches and we have arcs, volcanic arcs, the cascades are a wonderful example. The ring of fire, the whole ring of fire is basically this. And so if you're a Johnny Cash fan and they remember the ring of fire, ring of fire. Anyway, okay. So that was subduction pushed together with one side going under the other. We also noted that there is a different kind of push together as long as one side says, yeah, I'll go under, you go over, it's fine, they come together and one goes under. And what happens when two of them come together and no one will go down? They're both too buoyant, they stay on top and then you get a big collision. And so we noted that there is push together abduction. Abduction is against, obdurate. Obstinence is running up against. And so push together abduction and this is the big collision. Neither side goes down. So neither side down and so things run into each other and they get squeezed and squozed and folded and bent and you know, you get this kind of stuff going on. It's a real mess. The appellations are in abduction. The Himalaya today, the biggest mountain ranges are this. And so the Great Smokies are a wonderful example of what happens in abduction and the Himalaya today are the same thing and there are many other examples around the Urals are another example and so on. And so you get pushed together, folds, you get folds. So you end up with push together, folding and folding, you get earthquakes, all sorts of things happening, folds, folds, quakes, lots of activity. A thing that often happens, if you take something that's long and skinny and you squeeze it, it gets short and fat. And the mountains go up but the root goes down and so we talked about how as you squeeze things in abduction it makes a big root and the bottom of that root gets really hot and then erosion takes the top off and the bottom of the root bobs up and it brings very interesting metamorphic rocks and it brings ores and gems and all sorts of stuff out there. And so the collision thickens the rock and the mountains get a root. And so you might look at it as something like this. If one side is coming in and the other side is coming in and they're headed towards each other and then you have a giant collision. What do you end up with? This is at some time, this is early and then when you see this later what do you end up with? You end up with the top has been pushed up and the bottom has been pushed way down and in fact it goes farther down than it comes up and so you thicken it and you get a mountain and you get a root and then when you come in and erode the top the bottom bobs up and that brings hot stuff up to the surface and so erosion brings rocks from way down allows the root to bob up the way an iceberg bobs up if you cut the top off and it brings very interesting things from depth to the surface and so you can find rocks that are right at the surface that have been way the heck down earlier and that was sort of our complete texture of the big stuff. Now there's volcanoes and there's earthquakes and there's tsunamis and all kinds of dangerous things that go with this and we talked about those a little bit. We also talked about one other thing that was floating around here which is this was the interactions of the place but the mantle is still down there turning away deeper and occasionally there are these things called hotspots and the hotspots are coming from below the place they're coming from way down they're giant thunderstorms or giant atom bomb explosions that are coming from below and they're pushing off and they will poke through the place so we also noted that there are hotspots hotspots and they come from below the place they may come from the core mantle boundary probably some of them are deep and some of them are not quite so deep normally they're sort of like sea floor rocks they're basalts, they erupt quietly at volcanoes so they usually make quiet basaltic volcanoes and quiet means that it'll throw a rock a mile but it won't throw it a hundred miles because quiet basaltic volcanoes you still don't want to go have your picnic right next to one unless you're fairly careful the best example of this is the hotspot of Hawaii the giant island of Hawaii, the volcanoes there have all come from a hotspot feeding up from below it makes a mountain the mountain drifts away on the moving plate it makes a new mountain it drifts away and so on and so Hawaii is the best example of this occasionally a hotspot comes up below a continent and in trying to wiggle its way through the continent made of all that andesite with all that silica it gains silica and as it gains silica it may get water and then it becomes explosive and so Yellowstone is also a hotspot but Yellowstone when it blows up blows up really big and so occasionally a hotspot will get wet and silica rich coming through a continent gets water and silica from a continent and silica as it's trying to come through usually you're out in the ocean because there's mostly ocean but if you're coming through the continent when you get the silica in the water then you blow up Yellowstone is the best example of such a hotspot that we have today it may not come from as deep but there's this long trail the crater of the moon is out along the trail and the pot is still under there sort of under the northeast part of the park and it's still simmering under there getting ready to have the next big one so that is sort of how you make mountains that's all the big stuff drifting around that's sort of a whole story of what we did so far the next thing we did is to say ok mountains are not forever you put one up and something is going to beat up on it eventually and so we said hey what beats up on it we have the sun the earth's heat comes mostly from radioactivity the climate's heat comes mostly from the sun and so we said sun drives climate and climate makes rain and snow and we talked a little bit about how lifting air cools it and makes rain so that you can have the redwoods so lifting cools air because it expands and it's doing work and that cooling makes rain and that rain can give you things such as the redwoods which we enjoyed or I hope you enjoyed I love going to the redwoods so that was very nice but rain also beats up on rocks you put water in the cracks it freezes and expands you put water through the air and it picks up a little bit of acid you put acid on the rock and it changes it chemically and so the rain and snow and temperature and all the stuff of weather changing temperature and what have you ends up giving us beat up rocks it changes rocks and we called those changes weathering because they're done by weather this is really not rocket science so there's changes in rocks there's physical and chemical changes and what they do is they make little pieces where they make stuff that dissolves and washes away and so we looked at this as to give little pieces the little pieces give you soil you can grow crops because things get broken up like this and they give you things that dissolve and wash away and the little pieces sit around for a while and that soil and it's good but then they sort of slide down hill and that's mass movement and if your house is on top of that when it happens or if your house gets buried by that then that's bad and so eventually you get gravity pulls the little pieces down and so we call this mass wasting because it's mass and then you're sort of wasting it you're not keeping it on your hill or your farm and so mass wasting is moving things down and more or less naturally new little pieces are made about as fast as the old ones slide off and the sliding off may be very slow soil creep, you know, rock at a time go for a hill at a time or something like that it can be really fast the whole mountainside falls off and it buries the town and it kills everybody and it's not good and you call it a landslide or something like that but this goes from, you know, a fraction of an inch a year to 100 miles, 200, 300 miles an hour or more so there's this great, great range of things and eventually you get to the bottom of the hill but there's a stream there or glacier and so eventually the mass wasting feeds rivers and we look a lot at the very clear thing that a river is not a water pipe it is a water and sediment pipe it has to move the water it receives but it also has to move the rocks that are sliding into it or falling into it or creeping into it and if you tweak with a river it makes a difference you put a dam across the river and make a lake the lake fills with rocks and the river below the dam comes out clean and it picks up more rocks so it arose and so you go down the Grand Canyon and the fan bars are washing away because the dam is trapping the sediment the clean water comes out it picks up more rocks and so the rivers move rocks as well as water and you forget that at your peril some people have forgotten that on occasion and then they've ended up being very unhappy about that and so if you build a dam to make a reservoir the lake fills with rocks it may take a while it may be very fast some of them in one landslide it comes in a boom it's full already and it's not good with much and the clean water that comes out tends to wash away sand below and so clean water coming out will pick up more rocks and so there is a lot of effort going on in the Grand Canyon now how do we get sandbars back because the sandbars are where the cottonwoods root that grow up that the birds live and you know you need these for the ecosystem it's really hard if you're a deer to stand on the rock wall and get a drink you sort of want a sandbar there and so because the dam is trapping the sand the river comes out below the dam it washes the sandbars out of the Grand Canyon and so that's a big deal now if you get cold you don't get rivers you get glaciers and they pretty much do the same job they move rocks and they move water from high to low and so the river is taking the rocks and the water downhill and the glacier is taking the rocks and the water downhill too there are some differences glaciers do get to the ocean in Antarctica they do get to the ocean in Greenland they don't get to the ocean in many other places let me back up for just a second sorry I should have made a point about New Orleans so back up for a moment if you go back to rivers when you make a pile of rocks and mud it's sort of squishy and so when the river when the Mississippi gets down to the ocean it makes a big pile of mud and so New Orleans is sitting on some miles of mud the deepest piece of the Mississippi Delta is about seven miles thick and so when the river reaches the ocean it may make a big pile of mud called the Delta unless it all washes away if the river is really weak and the ocean is really strong it washes it all away to the beaches but if the river is strong and the ocean is weak you get a big pile of mud so it makes a mud pile and we call that mud pile a delta and the delta of the Mississippi is very deep and it's very long and it sinks under its own weight you make mud and watch it so it goes squish and so the mud squishes and if you put a city on top of that this is a technical term too mud squishes you put a city on that it squishes too and for years we taught students about what was going to happen in New Orleans everybody knew it it was getting lower and lower and lower as the mud squished and everybody knew that eventually the hurricane was going to get and it did and now they're taking your tax dollars and they're rebuilding it so it can happen all over again and then you can pay for it again and so New Orleans has been sinking and it will sink more and if they raise it up that will buy time it's only sinking sort of that much per year but eventually it gets there as the mud squishes there's some other things going on down there as well you pump oil and gas out from underneath and it squishes some more and you load it up and so there's all sorts of things there so that was back to rivers now let's go around and go back to glaciers glaciers are the cold rivers they put it down to go from where there's snow to where there's melt and there are lots of places across a third of the world that had glaciers fairly recently and so when we go looking at glaciers what we find is that they have been a lot bigger and a lot smaller we have ice ages so we see the history of ice ages and the ice ages were paced by the Earth's orbit the Earth's orbit has wiggles the spin axis if this is the north pole the spin axis has tilted over a little bit and it wiggles it goes a little farther over and a little less over and if you can think of my bald spot up here as being the north pole if it sucks straight up and the sun was shining in on my nose the north pole would never get a sunburn because it's kept over and gets a sunburn and if it tips over more and gets more of a sunburn it doesn't change the amount of sun reaching the planet but it changes whether it's on my nose it's getting sunburned or it's on my bald spot and so this and a couple of other wobbles this one and this one end up changing the sunshine and those have paced ice ages and so changes in the orbit paced ice ages these things take tens of thousands of years they don't matter for next year they don't matter for next century they do matter for a hundred thousand years from now and so this is slow over tens of thousands of years it was a very interesting thing though that if if my bald spot is getting more sun my nose isn't and there's some wiggles that mean when my bald spot is getting more sun that this out pole is not getting more sun but what's happened is the whole world has an ice age together and the whole world comes out of an ice age together and the remarkable remarkable result has been that as the sun changes in the north it changes dust fluxes to the ocean and some other things and that has affected CO2 and so what we have actually been able to see and this is a very interesting very useful result is that the north where most of the land is has controlled has controlled the world when it comes to ice ages so the world has bond with northern sun has followed the sun in the north the south is cold as when it gets the most sun and the reason is that northern sun controls CO2 and CO2 controlled the world's climate now how did that work we told you a story in the textbook which isn't complete the ocean is blue and it's not green because there aren't a lot of plants in some places and there aren't a lot of plants because there isn't a fertilizer and sometimes the fertilizer is iron and dust supplies iron and when there's an ice age in the north there's lots of dust supplying iron to fertilize the ocean to grow plants which pay CO2 and make plant which get eaten by animals get pooped into the deep ocean and that lowers CO2 in the atmosphere and that's part of the story but that's not the whole story don't get too excited about that particular one that controls the world's climate and this is one of many indications as we look at history to say CO2 matters if you tweak CO2 you're going to know about it something so we looked about that far and at that point Shridhar bid you a cheerful good day and he passed things over to me to chat with you and so at that point I'm going to stop for a moment I'm going to try to switch from microphone to another I'm going to try to switch to our words here and give you the rest of the story the rest of the song this will include some things that we haven't talked about in class but just give me a moment here the magic of technology the guys that set this up are really good in case you're curious wonderful people working for Penn State the education institute and other places here and so if we can get back on tone, I'm terrible on tone music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music music 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