Welcome, everyone, to our chapter 5 video lecture for Geology 101. Chapter 5 continues the discussion we began in chapter 4. Chapter 4, we talked about igneous processes, magmas and lavas, and how those molten materials can cool to form igneous rocks. This chapter is going to focus on the processes that allow for that magma to really form and then escape onto earth's surface as lava. If I were to ask you to kind of sketch out what a volcano looks like, I think most of us would come up with a similar feature. We might have kind of steep mountainsides with a little crater at the top. We might draw a little bit of gases coming out, and then lava moving down slope. And it is true, that is our conventional idea of a volcano. Even the emoji for a volcano looks something like this. A little bit better than what I’ve come up with, but as we'll learn, there are several different types of volcanoes. There will be different shapes. They will form in different locations. So, our definition of a volcano must be a little broader than just a mountain with a vent on top. We will see that some volcanoes are more hill shaped. Some are steep sided like the first doodle I had there. But what they all have in common is that they have a vent, and the vent is where lava escapes and erupts onto the surface. It's kind of the pathway between earth's interior and the surface. And we'll see that some of these vents are quite small, maybe have just a small trickle of lava, whereas some of these events can be quite large or explosive. And even though volcanoes often get a deserved bad wrap, right, they're catastrophes. They damage property. They often come with a death toll after an eruption. They can be quite devastating. We do owe them a little bit of gratitude though, because they helped to make our planet habitable. As we have big eruptions, like you see here with mount Pinatubo at the top, volcanic activity releases gases into our atmosphere. And these gases also include water vapor. So, in early earth, when volcanic activity was very common, our planet wasn't super habitable. We didn't really have surface water. We had very little crust. It was just a generally unpleasant place. Repeated volcanic eruptions, however, released the materials and gases that helped form our atmosphere, keeps us nice and insulated, as well as the hydrosphere, surface water that pooled together, together as the water vapor from volcanic eruptions cooled and settled to the surface. Volcanic activity is also responsible for creating new oceanic crust. In chapters two and in chapter four, we talked about the different types of plate boundaries and how they are linked to igneous material. At divergent plate boundaries, that's again where our plates are spreading apart, magma pushes up, pushing the plates apart. And as that magma cools, it forms new oceanic crust. So volcanic activity helps make our planet habitable. And it continues to expand our seafloor. Now, of course, I’m not trying to diminish the more serious implications of volcanic activity. In 2011, there was a massive eruption in Iceland. On the left bottom part of the slide, you can see a map with this kind of dark black cloud. See the north pole at the top and that teeny tiny red dot. That is the location of a volcano in Iceland that erupted. And the ash cloud was so intense from this eruption that it covered much of Europe, going into Asia, disrupting domestic and commercial air travel for up to 10 days. So, while the physical damages were small, right, the economic damages were considerable. Perhaps we are all familiar with Pompeii as well. We'll look at the eruption history of this area, specifically Mount Vesuvius, which in 79 AD erupted explosively, coating the nearby coastal town of Pompeii with a thick ash. This was able to preserve, unfortunately, the bodies of people living in Pompeii, as well as the infrastructure, the architecture, the frescoes painted on the ceilings and walls. So even though the eruption of Mount Vesuvius was catastrophic and devastating, it also allowed us to have insight into what life was like in 79 AD in this region, So, the title of this chapter is volcanoes and volcanism. Volcanism is simply the process by which this activity occurs. How magma rises up, pushing towards the surface. If we recall back in chapter four, we learned that magma is less dense than its surrounding material. It wants out. It wants up and out. Most magma in earth's interior never finds its way to the surface. But when it does, it escapes onto the surface, often bringing with it volcanic gases. And the combination of this hot molten material and gas moves and onto earth's crust, as well as into the atmosphere. We can see here lava is being discharged from a small vent in Kilauea on the big island of Hawaii. Remember that magma is the interior of our planet, whereas lava is once it's on the outside or exterior.
So, the volcanic processes or volcanism pushes that molten stuff out of the interior and onto the surface. When we categorize our volcanoes based on their eruption activity, we look at what we know about different volcanoes around the world and lump them into one of three categories: active volcanoes are those that have erupted in historic time. We have a clear understanding of its past eruption history. We can predict at least how the volcano will behave if it erupts. We are not really able to predict exactly when it will erupt, again, but we can kind of see, if it erupted a certain way in the past, it might give us some inclination of what might happen in the future. So, our active volcanoes we know that they've erupted before. Dormant volcanoes are those that haven't erupted in historic time but could. They show some activity. There's something still going on underneath that volcano. We just don't have evidence that it has erupted yet. That's the big word there – yet. The final group of volcanoes are those that are extinct or inactive. Those are volcanoes, they have the vent, but they have not erupted. They show no activity. We pretty much don't think that they will erupt in the future. Now, again, science is constantly evolving and so this grouping of these different volcanoes can change. But for now, if a volcano meets these two criteria that it hasn’t erupted and it shows no activity at present, it is considered extinct or inactive. So, traveling back across the Atlantic Ocean to Italy, I’d like to show this map of past eruptions of Mount Vesuvius, again in 79 AD. So long, long time ago this volcano erupted, completely devastating Pompeii. Was trying to find it on this map here. Here it is, down there at the bottom. This map only shows eruptions in the 200-year period between 1631 and 1831 AD. Each of those colored blobs, for lack of a better word, represents a singular eruption event. So, this pink eruption event, for example, which took place in 1631, it's very widespread. It reaches the coast. Some of the smaller eruptions do not travel as far, or they may be very low in terms of volume of lava. This little yellow deposit here, from 1813, is an example of that. Still, Mount Vesuvius is considered active. We know that it has erupted in historic time, it has had activity as recently as the early 90s. This is a very monitored volcano. We do have a good understanding of how Vesuvius can erupt, how it has erupted and that is because we have such a detailed history of this region. And volcanoes are not an earth-only process. We see volcanic activity on other planets, and in some cases, moons. This is a series of images, images of Jupiter’s moon Io. And in 2007, the new horizons space probe took a series of photographs that have been patched together here to show an animation of a volcanic eruption on this moon. It is incredibly large in scope. We can see it kind of rising up, almost like a blemish off the surface of that moon. But this shows that volcanic activity is not limited to just earth, that it can occur in many other places throughout the solar system. Now, earth is the most geologically active body in our solar system by far. Between plate tectonics, volcanic activity, there's a lot going on both in the interior of our planet and on the surface. But that doesn't mean that things like volcanoes are limited to earth only. They can be found elsewhere as we see here. In chapter 4, we talked at length about lava and magma. And we're going to look at different types of lava flows in just a minute. That type of material is not the only stuff that arises from earth's interior during a volcanic eruption. We can see that volcanic gases are also a major part of an eruption. Here is an image, or rather, it's a video of volcanic vents called fumaroles releasing volcanic gases onto the surface. I'll play this video in just a second here. But the key thing to take away from this, is that most of the composition of volcanic gas is water vapor, from about 50 to 80 percent. Again, early volcanic activity helped form our hydrosphere, and that's because of the repeated emissions of these volcanic gases. There are other kind of stinky things that can come out from a volcanic eruption. Sulfur jumps to mind. But really, the bulk of these gases is water vapor. So, let's take a quick look at this kind of animation. Keep an eye on these fumaroles. You'll see that it almost looks like steam coming out of a tea kettle. And this takes place in Yellowstone, sitting over a large magma chamber, that contains several geyser basins. We'll learn more about geysers in chapter 12.
So, you can see that there are a number of fumaroles in this region, again, all releasing that heated water vapor. Some carbon dioxide, nitrogen, sulfur. These, again, while the bulk of it is water vapor, they do have kind of that stinky stuff as well. Very impressive fumaroles. Some places that are very susceptible to volcanic activity, these fumaroles will just pop up along the side of a road. Now they're likely to be very hot. You should not go up and try to touch a fumarole. Of course not. And especially in Yellowstone, if you ever have the opportunity to visit, do not leave the designated pathways, as the materials both in this basin and in the fumaroles can be quite hot, and in some cases deadly, due to the heat. So volcanic gases are going to be one component of a volcanic eruption. The second component of a volcanic eruption will be lava flows. In general, lava flows tend to move very slowly. Rarely are they linked to fatalities. There can be explosive eruptions that are deadly, of course, but in cases like that of the big island of Hawaii or the recent eruption in Spain on la Palma, while the lava flows can move vast distances over the surface, it's not going to be like a tsunami wave. There's usually enough time to escape, evacuate, protecting human life. Property may be damaged as the lava flow moves across the surface, but saving lives is what's most important. And there are a number of ways that lava flows can cool, forming unique features on earth's surface. The first type of lava flow that we'll see it's called a lava tube. This is almost like a candy bar with an ooey gooey center. The outer edge of the lava flow will cool rapidly. It's exposed to the much cooler earth air compared to what's going on down beneath our feet. So, the outer edge will solidify into this thick kind of lava, igneous rock crust. But the inside of that lava tube is nice and insulated. It's kept nice and warm, so lava can easily flow throughout that kind of solid cavern.
as the lava moves away, it can leave behind these big empty gaps or caves. you can see a geologist on the big island of Hawaii walking over the top of a lava tube here, just to show you how large these features can be. now in some cases, lava tubes are much smaller. but this is pretty impressive, pretty cool to look at. The next two types of lava flows are named for Hawaiian words. We have pahoehoe, and aa, like you would say at the doctor's office. These are lava flows that are common on the big island of Hawaii or in the Hawaiian island chain. And they have distinct characteristics that allows us to differentiate them. Pahoehoe is very ropey, stringy, almost like taffy that is being pulled. So, you kind of yank it out. It's kind of stretchy. Pahoehoe is shown here on the bottom, it's very ropey, very stringy texture. Here on the top, this feature will be very blocky, very angular. It doesn't flow as neatly as pahoehoe does, instead kind of giving us these solid boulder shaped features. To zoom in and look at what a pahoehoe looks like as it's kind of moving here, we have an animation from the USGS, showing a geologist sampling a pahoehoe on the big island. So, let's take a look. So, we can see there's a ropey stringy texture in the background. It's still very hot in molten. The outside is cooling down first, but that hot kind of red interior is still visible in places. Pretty neat. Two more types of lava flow we'll look at: pillow lavas. These are going to be very common at divergent boundaries, where mafic lava or is kind of settling at the bottom of the sea floor. Remember at divergent boundaries, magma pushes up and kind of settles there as it does. So, it kind of takes on this billowy, rounded shape. So just kind of trickling up and settling down. Much of the oceanic crust is made up of features like this pillow lava. And if sea level falls, we can actually see pillow lavas exposed at the surface. Here in Alaska on the right, you can kind of see these rounded, almost blobs of igneous rocks that cooled as pillow lava settled at the sea floor. On the left, you can see an example from Oregon there. The last type of lava flow: columnar joints. These are really cool, because mother nature loves a pattern. We'll see patterns that repeat themselves across nature as we move through this class. As lava flows become stationary or stop moving altogether, we have time for the minerals within that lava flow to cool and set up a 3D atomic structure. And as that occurs, we start to see the lava flow consolidating into these polygon shapes. On the left bottom left, you can see looking up at devil's post pile national monument. You can see those columns kind of extending upward into the sky. If we were to stand on top of the devil's post pile, you would see something, or see a feature like that on the right there, where it is a flat smooth surface, but we have these polygons taking hold. These shapes appearing in that cooled rock. So, our first material with volcanic eruptions are volcanic gases. The second lava flows, we looked at five distinct types. The last type of material that can be ejected during a volcanic eruption are what are called pyroclastic materials. These are the solid stuff. So, it's not exact, but just to review: Gas would be the gases removed, The water vapor emitted during an eruption. If you think of molten lava as a liquid, it's kind of a stretch, but it's more of that liquid-like behaving material. The solid are the pyroclastics. These are the solid rocks, the ash, the things that come out and stay solid as a volcano goes boom. Ash is probably the most familiar to us. This is very fine, less than two millimeters in diameter. No different really in size than the ash you might see in a fireplace. As the material gets bigger, the pebble size, we'll see things like lapilli. And if we get into the centimeters to inches scale, we'll start to see volcanic bombs, which are smooth or rounded.
Or blocks which will be angular, sharp angles. We'll look at some explosive eruptions in a little bit here. But you can imagine that if an eruption is particularly explosive, the lava is coming out, so the gases are coming out. But we're also, sometimes, basically blowing out the side of a mountain. Those rocks gotta go somewhere. So, we call those our pyroclastic materials, our solid materials that come out with an eruption event. So, we're going to switch gears now and talk about the different types of volcanoes. As I mentioned earlier, if I asked us all to draw one, we'd probably come up with a mountain that, I’m sure yours is much more interesting looking than mine, that's why I went to school for science and not arts. But in general, right, the vent is what's important. We might have more of a rounded hill. We might have a tall mountain like the figure on the right. But in general, there is a vent that allows for that lava to escape. And this vent, depending on its size, can take on two different, can be named one of two things, I guess is what I would say. Smaller vents are called craters. One kilometer in diameter would be very small, right. So, this crater in Death Valley, you can imagine, you could not have a very long walk. These craters are less than, again, going to be smaller than many of the other features we see, but do form by an explosive collapse of the mountain top. So, if we have a massive eruption, as things settle down, it'll leave that kind of curved bowl-like surface. And at first, you might think one kilometer is large. But there are massive features much larger than craters and we call them calderas. These form when we have an enormous eruption. When the entire magma chamber beneath a volcano drains out, leaving a huge empty space. And everything, including the mountaintop, just collapses inward. So, this will be greater than one kilometer in diameter. And we'll see these huge bowl-shaped features, perhaps most recognizable is the caldera that sits in crater lake national park in Oregon. Now the name is a little confusing, but I assure you, that crater lake is a caldera. It is massive in size.
Let's talk about how crater lake formed. We started with mount mazama. Mount mazama was a volcano, high, with an elevation of Over 10,000 feet easily. Probably closer to, sorry I’m doing math in my head right now, probably closer to 12,000 feet give or take. Very impressive in size. And when mount mazama started to erupt, first ash was being ejected out of that magma chamber. You can see this likely took place out of the side of the mountain, and not necessarily the tip or peak. We'll see a little bit later, when we talk about Mount St. Helens, the 1980 eruption kind of behaved in a similar way. As the eruption continues and ash is released, we'll see that the summit or the peak will start to sink down. As that magma is released, the gases are released, the summit will collapse inward. Eventually, after all or most of that magma is released, the ash is gone, it leaves behind a big empty space. So, this feature here that you see in the second image, once it's all gone, gravity does the work, and pulls the summit downward, leaving behind crater lake, a large caldera. Today, the rim of crater lake sits at about 6,000 feet or so, which means that it almost halved in elevation. Now again, this is very rough math. But still it lost a considerable elevation when that peak collapsed inward. There is a small volcanic feature in the center of crater lake called wizard island. It is a small cinder cone. Very teeny, tiny, volcano. And there are, you know, there have been some small eruptions after this massive event. But for the most part, that magma chamber is drained, the explosive activity is behind this region. Here is another image looking out across the caldera of crater lake. Here is wizard island, the small cinder cone sitting in the center of the lake. So again, about 4,000 feet up, this mountain used to rise. Then, as the peak collapsed, it left behind this deep caldera, that again is over one kilometer in diameter. We've made the distinction between craters and calderas, now we will look at the four types of volcanoes. Volcanoes are going to be classified by two characteristics: their shape, and how they form. If we look at the animation or illustration, rather, on the bottom of this slide, you can see the four types of volcanoes are drawn from left to right: a lava dome, a shield volcano, composite, and cinder cone. The shapes are pretty different. Looking at these four, even though they're just illustrations, and as we move through this material, we will see how their formation varies. We're going to start with the shield volcanoes. Shield volcanoes are low and rounded. If you take captain America’s shield, and lay it on its side, you will see just a very shallow kind of bump. Not very dramatic. Very shallow slopes. These form due to the eruption of mafic lava flows. In chapter four, we learned that mafic material is lower viscosity, which means it flows more like water than honey. I'll say water, like, it's not exactly the same. So that mafic lava flow can reach kind of far out away from the vent, creating this shallow profile. We can see a famous example of the shield volcano here: Mauna loa in Hawaii. It is tall like a mountain, but it's still not as distinct or dramatic as the doodle I had been making earlier. It's very low, kind of rounded edge. The next type of volcano is called cinder cones. I often refer to these as baby volcanoes. As we saw with crater lake, after that massive eruption left behind that caldera, wizard island did pop up due to some kind of remnant eruption behavior. So, these will be very small compared to larger volcanoes, things like mount mazama for example. This is a tiny, tiny bit compared to the larger mount mazama. So, wizard island, as we saw in that image before, a small part of the caldera, is an example of a cinder cone. It will be steep sided, but often isn't the center of volcanic activity. This can form on the edge of a larger volcano, or in the caldera after a massive eruption. That is what we saw with crater lake. Next, we go to stratovolcanoes. This is likely what you imagine when you think of a volcanic eruption or a volcano. Stratovolcanoes are very steep. They're mountainous. They have these steep sides; they often erupt very explosively. They're very dangerous. We call them stratovolcanoes or composite volcanoes, because they have strata or layers. They are composed of different volcanic eruption events that kind of stack the different layers up top. So repeated eruptions, each time it erupts, it deposits new material, creating this massive steep stratovolcano feature. These will often occur at convergent boundaries. So, we'll see intermediate and felsic materials as one plate is subducted beneath another. We'll often see that material rising up, creating these stratovolcanoes. And most famously, over the last 50 years, Mount St. Helens. Excellent example of a stratovolcano and the explosive eruptions that we see in these locations. This image is from 1978 looking up at Mount St. Helens. This is a series of images actually illustrating the eruption itself. So again, we see that the primary eruption direction is from the side of the mountain, not necessarily the top. And it is so catastrophic, it is causing a massive landslide. We can see - wait for it - some volcanic blocks there coming out, because the pressure from this slow moving, high viscosity felsic or intermediate material, it builds up, and builds up, and builds up, eventually exploding. So, if we go back to our chapter four analogy of honey jar or a little plastic bear of honey, we squeeze the bear and the honey kind of dribbles out the top. So that's the kind of slow-moving eruption we would see in a stratovolcano. But if this continues, and we start to plug up the top of that little honey bear, eventually if enough pressure is applied, boom! All of that honey that was blocking up the tube is released at once, creating this massive eruption. And as I mentioned in chapter one, mount saint Helens, we did a pretty good job of closing off the area. Geologists worked with the governments to make sure people were safe. But even still, there was a loss of life, including a geologist who was surveying this region from over a mile away. Parts of his vehicle have been found. But Daniel Johnston and his remains have never been found. His last words were radioing into the United States geological survey with “Vancouver! Vancouver! This is it!” Meaning the eruption is coming. And today one of our volcano monitoring stations is named for David Johnston. It's a dangerous, dangerous job, and I have a lot of respect for the geologists who choose to study volcanoes. I, myself, am a bit of a fraidy cat. I'm comfortable behind my computer. Right. The last type of volcanoes that we will see lava domes. Lava domes form just like our honey jar. As we squeeze out that high viscosity material, it doesn't really flow. It just kind of sits right on top of the vent. So, these felsic or intermediate magmas just kind of rise up and sit there. They're so resistant to flow, they block up the larger volcanic vent. That's why they're often called plug domes. If the pressure beneath gets too great, these plug domes will erupt in a very violent and destructive eruption, because the pressure has to be great enough to basically push loose that plug of volcanic material that's blocking the vent. So, often, we'll see that these lava domes get to be quite large in size. An example would be Lassen peak here in California. Again, it is felsic or intermediate, giving it that light color that you see there. When we have these massive lava dome eruptions, they're often accompanied by nuee ardente. Nuee ardente are these pyroclastics, remember that's the explosive solids, that come with an eruption. And when these pressures are so great the nuee ardente is a massive cloud of volcanic bombs, blocks, ashes, gases, that can be quite devastating in their own right. So, it's not always just the lava flow itself that people need to be afraid of, although our disaster movies might tell us otherwise. The nuee ardente can be quite, quite devastating in its own right. And we saw that with Mount Pelee in Martinique. Nuee ardente took the lives of 28,000 people after this eruption. There were only two survivors in the region. One was in a prison cell contained beneath the ground. One person was found severely injured on the edge of town. There was a small child, a little girl, who was found after the eruption afloat in a boat. It is believed that she may be a survivor of this event as well. But still, of 28,000 people two or three survivors. That's just a catastrophic event. And this took place in, I believe it was the 1920s. I don't have these; I should put the year on there. So now that we've introduced the four types of volcanoes, we looked at how they differ in their shape, their size, and how they form, I’m tying our types of volcanoes back to the four groupings of magma, lava, or igneous rocks. Recall, on the left side ultramafic and mafic are called low silica, whereas intermediate and felsic are the high silica examples. High or low silica. Ultramafic is found in the mantle, very deep in earth's interior. So, we're not going to really see that with our types of volcanoes. Cinder cones and shield volcanoes will often be composed of or erupt mafic material. Stratovolcanoes usually sit right over the intermediate category, whereas lava domes can kind of straddle that intermediate or felsic zone. This is just to summarize what we just learned and then tie it back to chapter four. When we talk about volcanic eruptions, at least us here in south Louisiana, we're pretty secure, as we saw with the earthquake distribution. These volcanic eruptions are often limited to well-defined zones, matching plate boundaries. The circum-pacific belt, as we learned in our chapter 8 on earthquakes, is home to about 80 percent of all earthquake events. We also have a good number of volcanoes that dot the edge of this circum-pacific belt. We call that the ring of fire. If you look at this map here, you can see those little red triangles represent individual volcanoes. So quite extensive throughout the region. The Mediterranean belt, again for earthquakes, this was home to approximately 15 percent of all earthquake events. We can see that in this area, in this purple kind of rectangle, there's not nearly as many volcanoes as we see in the ring of fire. But they're still present. For example, we can see in Italy things like Vesuvius located there. So as with earthquakes, most volcanoes fall within these defined zones, aligning with our plate boundaries. And as promised, it's going to keep coming up. How does igneous activity differ at our different plate boundaries? You know I’m going to tell you! At divergent plate boundaries, we're largely going to see mafic magmas as the ocean is ocean floor is pushed or spread apart by rising magma. This material that is mafic in composition will cool naturally giving us this dark black basalt or gabbro or pillow lavas. So divergent plate boundaries things like our oceanic ridges. Seafloor spreading zones.
We're going to see a lot of mafic material. And that is why our new oceanic crust is going to fall in that mafic category. It's not all beneath the sea, though. I include this picture here of Iceland to show that we can see some divergent plate boundaries on land. Most are going to be found in the ocean, but there are exceptions to the rule. At convergent plate boundaries, we will have one plate subducting down and another plate sitting atop. When we have that plate being pushed or subducted down, it will kind of melt, causing intermediate or felsic magma to want to push up and rise creating volcanoes along these convergent plate boundaries. So, the volcanoes of the pacific northwest, also along the western edge of south America, these convergent plate boundaries are characterized by extensive composite volcanoes or lava domes. Very slow moving, high viscosity stuff. Lighter in color, found throughout the circum-pacific ring of fire and the Mediterranean zone. We learned in chapter four, transform boundaries, we're not gonna see volcanoes there. So, we're gonna skip over that, and instead go back to a topic we covered in chapter two. Hot spots. There are places in the center of tectonic plates where, as they move over a stationary mantle plume, new volcanoes pop up and form. These hot spots can build from mafic lava, building those shield volcanoes, those kind of slow rounded, low slope profiles. Hot spot volcanism is how the island chain of Hawaii was formed. The pacific plate slid over that mantle plume, and as that took place, these volcanic islands started to pop up. To summarize just as we did with the types of volcanoes, again, ultramafic is going to be really constricted to our mantle. We will see at divergent boundaries and hot spots mafic material. So again, that's kind of the lower silica. At convergent boundaries, we're going to range from intermediate to felsic or high silica features. So, this is a good review slide to kind of keep these features straight as you're preparing for your exam. The last topic I want to cover is how we characterize volcanic hazards. We talked about a number of pretty devastating events throughout this class, ranging from Mount Pelee uh Mount Vesuvius, Mount St. Helens, the eruption of mount mazama. And as scientists, we want to be able to compare these events to each other. And we do so using what is called the volcanic explosivity index or VEI. The VEI does not take into consideration how many homes were damaged, how many lives were lost, not even the speed of lava. What the VEI is interested in is the volume of material ejected upward and how high that plume goes. The higher the plume goes, the more material ejected upward, right, the more explosive you would imagine that eruption to be. So, this ranges from gentle to explosive to cataclysmic. You can see at the bottom here, gentle eruption, that volcanic plume does not necessarily go so high. Whereas the VEI of four to seven falls in the cataclysmic range because the volume of material ejected upward, as well as the height of the material, gives us a very explosive event. To put into perspective how some of these events, what they might look like, the mount Pinatubo eruption in 1991 had a volcanic explosivity of six. So, this falls in that cataclysmic range. Now this took place, again, in the Philippines not far from a U.S. military installation. So, there was a good amount of forecasting that was done in this region, so the fatalities were low. due to the forecasting, you know, evacuation orders, now many people were left without a home, given refugee status because of this event. It was still quite devastating, because again, it is a really just explosive massive event. On canvas, I have a short video, it's less than 10 minutes. I want to say it's like seven minutes long from pbs talking about how U.S. Scientists forecast mount Pinatubo, the different pieces of evidence that they used to at least say something was going to happen. Now prediction is not black and white. They weren't able to say the eruption will occur on Tuesday morning at 9:22 am until, you know, 2:53 pm. That's not what forecasting is about. It's about removing people from unsafe situations. So, as you watch this video about forecasting mount Pinatubo, you'll see a number of these different forecast methods used to predict when or if a volcano may erupt. May being the operative word. There so definitely check out that video, it is fair game because it ties in what you see on this slide here. So, this is it for our chapter 5 lecture on volcanoes. Hopefully, you see now how it ties in so nicely to our chapter 4 lecture on igneous rocks. Take what you've learned here and chip away at the chapter 5 MindTap homework. And as always, if you do have specific questions for me, there's the discussion board or my office hours, where I’d be delighted to talk with you about specific events, questions you may have, anything of that nature. All right. Happy studying, everyone!