 Alright, let's talk the ring of fire. What is the ring of fire? Where is the ring of fire located? And what causes the ring of fire? First step in our journey is to take a look at what the inside of the earth looks like. So here's the earth and I'm cutting it in half. So now I can see the earth and all of its layers. It actually looks sorta like this. I mean this is a fantastic rendition. So the earth is comprised of a series of layers. The first layer that we find inside of the planet is called the inner core. And the inner core itself is right at around 720 miles or so in thickness. Surrounding the inner core is the outer core. And the outer core is also metallic, but it's so hot that it's liquefied. So what we actually get is a liquid outer core and the liquid outer core is right at around 1300 miles or so thick. Now we're getting a little bit thicker. And again, this image is not to scale. As we continue outward, we next hit the lower mantle. So we'll call this LM for lower mantle. And the lower mantle is about the same thickness as the outer core, right around 1300 miles or so. As we proceed upward, we now hit the upper mantle or UM. And the upper mantle is relatively thin, only at about 400 miles or so of thickness. So when you add up all these numbers, we get right around 3,900 miles, which would be the radius of planet earth. So we're a relatively small planet. The very top layer of the earth is called the crust. And the crust ranges anywhere from eight miles, perhaps up to something like 40 miles or so. You might find some places of crust, which is thinner like the oceanic crust, which is that layer of rock beneath the ocean. That could range actually anywhere from three to eight miles. And that's gonna be more of an iron rich, basaltic type rock. And then you have your continental crust, which is what we live on. And that can range anywhere from 20 to 43 miles of thickness or so. And the primary ingredients of the continental crust are gonna be iron and silicon and aluminum, which makes up more of a granitic type rock. Okay, so we've got the crust, the upper mantle, the lower mantle, the outer core and the inner core. But we still haven't talked about the lithosphere. Well, what the lithosphere is, is the crust plus the uppermost part of the upper mantle. That is lithosphere. Now, why is lithosphere so important? Well, lithosphere resides on top of another layer, also found in the upper mantle. And this layer is called the ethenosphere. So let's put that down. Now, here's the thing. Lithosphere is thin. It's 63 to 400 miles or so in thickness. And again, comparatively speaking to the radius of the earth, that's not much. So the lithosphere is thin and brittle. The ethenosphere is a solid, but it actually can flow like a liquid. So the ethenosphere is a solid, but flows like a liquid. And it does. So as the ethenosphere moves, the lithosphere, which resides on top of the ethenosphere, has to move as well. But because the lithosphere is so thin, relatively speaking and so brittle, over time the lithosphere has broken up into a series of individual lithospheric plates. And these individual lithospheric plates all move with the movement of the ethenosphere. And there's about 26 or so major lithospheric plates. So let's take a look at this idea a little bit further. What we wanna do, again, is draw our cross section, but we're gonna draw it a little bit differently now. So here is our crust plus our upper mantle, and we're just gonna draw the core as well. So here's our core, and here is crust plus the uppermost part of the upper mantle, which we'll call lithosphere. So I'll just put a bunch of Ls here. And then beneath the lithosphere is the ethenosphere. And if you're wondering how thick the ethenosphere is, that's also relatively thin. We're talking maybe about 300 miles or so in thickness. So it's a little bit thicker in some places than what the lithosphere is, but it can also be a little bit thinner too in some places than what the lithosphere is. Now the next question is what promotes this ethenosphere to move? And the answer is energy with inside the Earth. And the energy within the Earth is really gonna come from three different areas. One is gonna be radioactive decay. So inside of the Earth, we have elements that are decaying radioactively. And when they do that, they release mass and this mass turns into heat energy. So radioactive decay is one source of energy. Another source of energy is just pure pressure. There's a lot of pressure pushing down on any of the molecules and atoms down here toward the core and that pressure itself is gonna generate heat. And then finally three, we have molecular collision. So down here in the depths, molecules and atoms collide and when they do, that too is going to promote a heat exchange. And we can talk specifically in the outer core. Remember the outer core is that metallic liquid. So we have a fair amount of movement in that outer core that promotes the collision of particles and those particles colliding create heat as well. So we are generating heat inside the planet and where does this heat go? The heat's going to go up. And when it gets up, there's gonna be a movement. There's gonna be a convection of material. So anything that's up here is going to be moved and displaced and get pushed down here. And what we're really talking about is the movement of energy, our convection of energy inside of the planet. Well, you'll notice that if I've got convection going this way, right here, I can have convection going the opposite way. So let's suppose that this convection of energy promotes the movement of the ethiosphere. The ethiosphere over here is gonna move in this general direction and the ethiosphere over here is gonna move in this general direction. And again, as the ethiosphere moves, this lithosphere is going to move as well. But remember, the lithosphere has been broken up into a series of plates. So over here, this lithosphere is broken up and it's gonna move in this general direction with the movement of the ethiosphere. And over here, this lithospheric plate is gonna move in the opposite direction. We would call this a divergent plate boundary. So this whole lithospheric plate moves, this whole lithospheric plate moves as well. Well, what about here? We're not gonna get an empty void. Rather, what we will get is molten material coming from below, seeping upward and filling in the gap created by this movement of the lithosphere. And as a matter of fact, this is how we create oceanic rock or our oceanic crust is formed via this process here. So we're not gonna have gaping holes on the planet, but rather as the lithosphere moves, molten material from this movement of energy and materials below is going to fill in these empty voids. So the interesting thing to note, if we take a look at this movement of energy with inside the earth system, we can have energy that's moving like this. And again, this is going to lead to divergent plate boundaries. But what if we have energy colliding like this? And so this is the appearance of our convectants, or of our convective cells. Well, if that's the case, then the lithosphere over here is going to move this way. So now you'll notice I've got two lithospheric plates that are actually coming together. So here we have convergence as two plates are converging together. And here we have divergence as two plates are diverging apart. Here we know we're gonna get this nice movement of molten material creating sea floor. And this oftentimes leads to what we call volcanic action or sea floor spreading. So the earthquakes here are gonna be, so over here we're gonna have this movement of molten material create rather subdued or oftentimes what we, so right here this movement of energy is going to create some nice volcanic activity, but more akin to the what we call shield volcanoes where shield volcanoes are relatively quiescent and not particularly explosive, but they're just a seeping of molten material coming upward. Very much like Hawaii for example. We'll see this type of divergent processes in places like Iceland. So what's created Iceland has been the mid-Atlantic rift system. So Iceland itself is actually a volcanic either created from this divergent process. But when we talk about convergence, a variety of different things can happen. For example, if we have two converging continental plates, so here is continental crust and here is continental crust. If these two continental plates collide, then what's going to happen is we'll get this incredible collision and potentially a bunch of uplift. So we will create some really interesting convergent mountains. The Himalayas are a great example of this. As the Indian subcontinent collided with the Eurasian plate millions and millions of years ago. The Himalayan mountains, by the way, are still growing today. The highest point is Mount Everest at 29,000 feet, but that mountainous range is still growing from one to three centimeters annually due to that continual collision of the Indian subcontinental plate and the Eurasian plate. This is one example of two plates colliding, but there's another example of plates colliding. What if we had a continental plate colliding with an oceanic plate? And an oceanic plate would be a plate that's literally above the ocean, or excuse me. And an oceanic plate is a plate which literally has oceanic crust as its primary layer, whereas the continental plate predominantly has that continental material or that granitic rock. If these two plates collide, then there's gonna be something called subduction, and there's gonna be subduction because one plate will be heavier than the other plate. Well, as it turns out, oceanic crust is heavier than continental crust. The oceanic crust is basaltic rock. It's very much iron-rich. The continental crust is granitic rock, which means there's some iron in it, but there's a lot of silica as well, which is lighter in weight. So when these two plates collide, the oceanic plate will be subducted beneath the continental plate. And as that occurs down here on what we call the Benioff zone, we're gonna get a lot of melted rock. And as this rock begins to melt, it'll create what's called magma chambers, which are chambers of molten rock. And these magma chambers will begin to lift upward and seep upward. So it'll move up through the continental crust. It'll eventually break through and create volcanoes. We would call this a volcanic arc. A nice example of this would be the collision of the Nazca plate in the South Pacific colliding with the South American plate. And this whole process has created the Peru Chile Trench, which is right here, because you'll get a nice trench system as well. So this is the Peru Chile Trench. And you also have the Andes Mountains. So this mountain range was created from this type of oceanic continental collision. But there's another type of collision as well, not just the one where we've got a continental, continental collision creating something like the Himalayas, for example, or an oceanic continental collision creating something like the Andes Mountains will also have an oceanic, oceanic collision. So for example, if we take a look at the Japanese sea, we've got the Pacific plate colliding with the Eurasian plate. So here is the Eurasian plate and here is the Pacific plate. The Eurasian plate actually has a fair amount of material that is underwater. And the Pacific plate, of course, is Pacific plate and most of it is oceanic. So when we talk about the Eurasian plate's ocean water, but the Eurasian plate itself extends out into the sea, this is not, excuse me, this is not the basaltic rock that we know of when we talk about oceanic crust. Rather here, we've got some granitic rock whereas here along the Pacific plate, it is that basaltic rock, the heavier stuff. So when these two plates collide, when these two oceanic plates collide, the Pacific plate is going to get subducted beneath the Eurasian plate. Here along the Benioff zone, we'll have our multi-material, it'll seep up and it'll create volcanic islands. So here again, we are at sea, which means we're gonna create volcanic islands versus the Andes Mountains, which is created on the continental crust itself. This is a fantastic example of a place like Japan. So Japan was formed in this process with the collision of the Eurasian plate and the Pacific plate, but there's actually something else missing in this picture and that's the Philippine plate. And the Philippine plate collides here as well, which is gonna be really important in our discussion in just a second. Now, I haven't showed you any maps yet, so let me show you a really nice map. Here is what we were just talking about. Here is the convergence of the two continental plates, the Indian plate and the Eurasian plate, leading to the creation of the Himalayan Mountains. Here's a divergent plate, the South American plate diverging from the African plate. And this line here is called the Mid-Atlantic Rift System. So the whole divergence along here actually created the Atlantic Ocean and here's Iceland. So again, Iceland is the divergence of the North American plate with the Eurasian plate and here we have that nice volcanic island and you might be saying, well, why do we have volcanoes and volcanic islands all along this Mid-Atlantic Rift Zone? And the answer is there is, they're just underwater. Here with Iceland, Iceland is in a shallow part of the North Atlantic. It's seeped above the water line and that's why we see an island there. And then finally we can take a look here and here's Japan. And here's the collision of the Pacific plate with the Philippine plate with the Eurasian plate. Okay. Oh, by the way, there's one other thing that we have to look at and that third type of plate boundary because there's three types of plate boundaries. There's convergence, there's divergence and there's also something called transform. So here's a transform plate boundary where two plates are moving adjacent to one another and you'll see transform plate boundaries in this type of picture. So here in the Aleutians, this is convergence and down here, this is divergence where we've got the Nazca plate diverging from the Pacific plate. So if you have divergence and if you have convergence then there has to be a transform there. And let me show you here in a clearer picture. So here is convergence, here is divergence. Well, what about here? And what about here? This plate is moving this way relative to this plate which is moving that way and this is called a transform boundary. We'll just label with T. Okay, now why did we spend all this time talking about convergence and divergence and transform? Well, remember the whole gist of our conversation was we wanted to talk about the ring of fire. We wanted to talk about earthquakes and volcanoes. Well, we already know from our discussion that right here when we have convergence we can get volcanic activity. If we have divergence we can get some volcanic activity as well. So divergence, convergence leads to volcanic activity because molten material from below is going to come up. But anytime you have the movement of the earth, the movement of earth's crust, in this case the movement of the lithosphere you're going to have friction. And so here if we draw this picture of our subduction notice we have one plate subducting beneath another. So right along this zone, the Benioff zone we have friction. One plate is moving this way, one plate is moving that way. They're colliding with one another. There's a frictional energy buildup. The frictional energy buildup will get to a point where it has to be released. The release of that frictional energy buildup is the earthquake. So the earthquake itself is gonna be this movement of energy due to the friction creating that buildup. And just in terms of nomenclature the point of release of energy is called the focus and the point right above the focus on the surface is called the epicenter. So we already know that if we have a convergent zone we're gonna have potential earthquakes because there's frictional energy buildup. If we have divergence we can have the same thing though because again we've got multi-material seeping upward there's a movement of earth's material and anytime you get a movement of earth's material you can have frictional energy buildup which could inevitably lead to an earthquake. If we have a transform boundary it's the same. We can get a frictional energy buildup once again with one of the most famous transform boundaries on earth being the San Andreas fault line that's going across California. So again anywhere where there is earth's movement along these plate boundaries there can be frictional energy buildup that frictional energy buildup can lead to earthquakes. Okay so with all that said let's take a look at the Ring of Fire. Here it is. The Ring of Fire is the entire Pacific Rim. So all around this Pacific plate it's called the Ring of Fire. It's called the Ring of Fire because we have both earthquakes and volcanoes all around this rim. Well why do we have earthquakes and volcanoes here around the Ring of Fire? You can answer that question because you'll notice here these are all convergent zones. So this is convergent and this is convergent but right here we have divergent and right here we have divergent. So convergent, convergent, divergent and right here transform. So this whole area around the Pacific Rim the Pacific Plate is the Ring of Fire where we find earthquake and volcanic activity. Curiously too let's go back and take a look at Japan. We can see it on this map but we'll take a look on this map even better. Again here is Japan and Japan is literally the result of the collision of the Pacific Plate with the Eurasian Plate with the Philippine Plate. So you have three plates colliding. The amount of energy buildup along that region is substantial. So there are many earthquakes that occur in Japan. There is big volcanic activity that occurs in Japan as well i.e. Mount Fuji. And with this earthquake activity and with this volcanic activity you can have other forms of destruction like tsunamis which we'll talk about at a later date. But that's it. That my friends is the Ring of Fire right here along the Pacific Rim. And so again we talk about Japan. It's on the Ring of Fire. We talk about the West Coast of North America. It's on the Ring of Fire. We talk about the Aleutians in Alaska. Ring of Fire. Indonesia. Ring of Fire. South Pacific Islands. Ring of Fire as well. Anywhere along this ring we're gonna find a fair amount of geologic activity. Okay that is it. Thank you very much for watching and until the next time I will see you later.