howdy again everyone and thank you for continuing on with module six in this video we're going to focus specifically on explosive eruption landforms what are some of the types of things that are formed by these explosive eruptions now there are three different main types of land forms of explosive eruptions that we're going to focus on in this class and we're going to call them composite volcanoes which are also called strat volcanoes these are conicle volcanoes they're shaped like a cone and they're built up of many layers of hardened lava and tera or ash we're also going to take a look at cinder cones which are also conical in shape but they're made up of loose pyrolastic fragments like ash or cinder that has been built up around a volcanic vent and then we'll look at calderas the large depression that's formed when a volcano erupts and collapses think like you have a full balloon underneath a sandbox volcano and it pops creating a depression in the volcano where the balloon once was same thing has happened with volcanoes except the magma chambers your balloon and the pops and eruption now we're going to take a look at all three of these landforms in greater detail next starting with our composite volcano again these are also called strat volcanoes they're conicle in shape so they're shaped like a cone as you can see here in this figure and they're built up by the many layers of hardened lava and tera tepher is a fancy word for ash so this is kind of the classic volcano that we think of anytime you hear the word volcano that perfect cone-shaped mountain with a vent on top it's shaped that way because it's built up by the layers of previous old eruptions it gets bigger and bigger and bigger the older it gets right so we have many layers of lava and ash that are building up this cone and they're called composite volcanoes or strat volcanoes now where would we see these we see them uh around subduction zones the Ring of Fire um primarily and we have lots of strat volcanoes or composite volcanoes in our own country here's Mount Reneer in Washington um Mount Reneer could be considered one of the most dangerous volcanoes in the continental US and we'll talk a little bit about why that is later on with this module but if you take a look at the background of this photo you're going to see another cone-shaped mountain that is Mount St helens now Mount St helens doesn't look like that today this photo was taken before it erupted in 1980 so these eruptions can change the face of our volcanoes um and we'll look at that when we get to case studies that Mount St helens eruption but these are in our own countries we got our composite volcanoes in our own countries a beautiful example of a composite volcano at least my favorite is Mount Fuji in Japan mount Fuji is so beautiful it even looks peaceful however this is a very dangerous volcano um that is capable of producing some really intense explosive eruptions and will produce an explosive eruption again in the future but Mount Fuji sits on a subduction zone the ring of fire it is a direct consequence of those plate tectonics um and it's producing that explosive landform there now the Cascade Range we don't just have Mount Reneer and Mount St helens it is full of these composite volcanoes it is littered with them because remember we have this subduction zone off the coast of California Oregon and Washington the Cascadia subduction zone creates the Cascade Mountains so that Wandafuka plate subducting underneath the North American plate producing these volcanoes on the continental side that include Mount St helens and Mount Reeneer but we have lots of other active volcanoes here we got Mount Jefferson Mount Hood Mount Adams here's Middle Sister North Sister South and you can see it's just littered with volcanoes and and they're all explosive volcanoes so it's important that we study these kind of processes because these things exist in our own country so here's just showing the last eruptions in the Cascade Range during the past 4,000 years you can see the most recent example being Mount St helens and you can see Mount St helens has erupted many many times in the past and it will continue to erupt in the future as long as our plate tectonics are going in the directions in which they're going today which they probably will continue for quite a while but you can see Mount St helens isn't the only eruption that we've had in the past 4,000 years we've had many eruptions mount Reneer has erupted many times um and you can see just how many eruptions actually exist here in the United States because of these um subduction zone processes and then here it is Mount St helens this is 1980 eruption i don't need to tell you what type of eruption this is is it explosive or eusive hopefully you get that it is definitely explosive um and this picture isn't in black and white but it looks like it because there's so much ash involved that's really just creating a blanket of gray everywhere you look and and we're going to look at Mount St helens more closely at the end of this module all right so some other explosive landforms that exist we have these things called cinder cones um these are smaller than our composite volcanoes uh but they also have steep sides and they're cone- shaped now cinder cones tend to be more explosive than our shield volcanoes which we're going to get into next with our with our eusive eruptions but they can actually be found on the side of some of those shield volcanoes and they exist as kind of parasitic cones and we'll see some pictures of that later but these cinder cones have eruptions that are characterized usually by a lot of ash and cinders cinders are gravel- sized ash gravel sized terra and that's exactly what's shown here so those lava rocks those those um landscape rocks that's actually what ash looks like when it gets to that size so ash is those things just at a more microscopic scale so you can see why hazardous how hazardous ash actually is it's very sharp very rough but gravelized ash called cinders cinder cones are made up of layers of these cinders so here we have our cinder cone again cone- shaped conicle shaped just like those composite volcanoes but at a much much smaller scale and instead of being made up of hardened lava and ash these are made up of loose pyrolastic fragments like those cinders that I just showed that have been built up around a volcanic vent over time so here are some perfect examples of cinder cone volcanoes this is Paracutin in Mexico you can see here that it it looks like it's built up of loose pyrolastic materials um it is much smaller than our composite volcanoes but yes they do indeed um produce explosive eruptions as you can see one in the photograph on the left but cinder cones can also be found on the slopes of Shield and even composite volcanoes um they're kind of like smaller parasites that exist on other side vents of a volcanic system this is um these are some examples of cinder cones that exist on the side of a much larger volcano Monaloa in Hawaii and Monaloa is a shield volcano a fusive volcano that we'll talk about in the next video but we have these cinder cones that exist off the side of Monaloa as well now this is a cinder cone volcano in Arizona yes Arizona might not have active volcanoes but it definitely had volcanoes in the geological past this is a perfect example of one again these cinder cones um there are these piles of cinders piles of those um ash that kind of form this angle of repose just that loose material that's just built up over time and what's really interesting about this photograph you can see here clearly the cinder cone this is a volcano but if you look at this dark stuff out in the distance this is actually an old lava flow so you can see it also produced lava that flowed in this direction now this is a cinder cone in a volcanic field near Mary's Utah so this is Utah utah also had volcanic activity around the same time as Arizona and this is my own photograph i was able to climb to the top of this volcano and I can tell you with firstirhand experience that these cinder cones are indeed made up of very sharp loose pyrolastic material and those cinders those lava rocks are actually very hazardous and it cut up the soles of my boots that's how sharp these rocks can get um they literally cut up the the bottoms of my boots as I was climbing up this thing and then there's me um I hiked up there we did some geologic work up there um if you do decide to become a geology major you really do get to see awesome parts of of our own country and maybe even sometimes the world this is me when I was an undergraduate student um at Ohio State so we did do field camp which is just a highlight of a geology degree and um we got to have lunch up on the top of this volcano it was actually really cool not that I'm trying to convince you to switch your majors but I'm kind of trying to convince you okay so we got composite volcanoes we got cynic cone volcanoes we also have calderas now calderas are formed from the collapse of a composite volcano and this diagram really nicely shows how that happens so we have a composite volcano it starts to erupt it's explosive we get lots of explosions and sometimes if that whole magma chamber empties itself up or the explosion just ends up being large enough it can blow the top of your volcano away um and we're going to create a crater especially if that magma chamber is completely empty it'll also sink into that chamber that creates that caldera um and if this volcano remains active we are going to continue to get magma being fed back into the system and that's going to create a new volcanic cone to begin growing to begin the life cycle all over again it's actually pretty cool stuff but these are a direct result of a very explosive very dangerous process and this is exactly what happened with the formation of Crater Lake in Oregon i don't know if anyone's been to Crater Lake i definitely want to go to Crater Lake but Crater Lake um is the result of a caldera formation it formed from a huge violent eruption an explosion of Mount Mazama 7,700 years ago and you could see even a new little baby volcano starting to form and just another picture of our crater lake again this is the new little baby volcanic cone that's forming in the middle of that caldera but Crater Lake isn't the only caldera volcano that we have here in the United States we have a giant one sitting right where Yellowstone National Park is you probably heard about this there's probably some movies about this that try to scare you into its explosion well this this actually is kind of scary guys um but we don't anticipate it erupting anytime in our lifetime however Yellowstone National Park is sitting in a major caldera of a past explosive volcanic eruption now I'm just introducing it here we'll talk more about Yellowstone and and what makes it so dangerous later on in this module but first we need to get to our other eruption type with ausive eruptions i'll see you there