Building up and breaking down

Transcription

1 Building up and breaking down

2 There is one major explanation for how Earth s surface is built up, this is explained by the idea of continental drift. Continental drift causes a few things like volcanoes, earthquakes, and hot spots on Earth s crust.

3 Next year in sixth grade you will learn all about convection, but I will teach you a little bit about it right now. Convection is a process where heat moves up to the top of something, spreads out across the top of that object, cools down and falls back towards the heat source. Imagine a fire built in the middle of our classroom. How would the heat make the air in the room move?

4 The continents sit on top of a half-liquid melted rock goo that moves in giant convection circles. This causes the crust to snap into huge pieces called plates, and these plates are what we are actually riding on. Sometimes these plates behave while moving most of the time they do not.

5 Spreading Mid-Ocean ridge Rifting Coming Together -- Subduction -- Collision Transform -- Strike / Slip -- Dip-Slip From these different kinds of movements you get volcanoes and earthquakes.

6 At the bottom of the Atlantic Ocean about ½ way between the continents the sea floor is a huge mountain chain. This is because the ground on both sides of these mountains is moving away from the ground on the other side. Each time it moves magma (melted rocks) shoots up out of the crack and is cooled almost instantly by the water, this makes an undersea mountain.

7 Some underwater mountains get so high that they break through the surface. Iceland is a good example. Iceland is splitting apart and growing. Iceland s volcanoes are little more than cracks in the ground that magma comes out of.

8 Sometimes plates spread on the land s surface. When this happens it takes many thousands of years for the cracks to get deep enough for magma to come out, but you do get some very deep valleys. Often times these rifts are hard to see because they will fill up with water. Lake Baikal in Russia is a good example, it is the world s deepest lake, and it holds more water than any other.

9 In subduction two plates are crashing together. Ocean crust is thin and heavy like chocolate. Land crust is thick and light like marshmallows. The light crust rides on top, and forces the ocean crust down into the hot mantle of the Earth.

10 Subduction zones have the world s most powerful earthquakes. Also when the Ocean crust melts it starts to rise to the surface and it makes volcanoes. A great example of this can be found right here in America. The Cascade Mountain Range is a chain of volcanoes. These mountains start in Northern California, run through Oregon, and Washington, and on into Canada.

11 When two chunks of Continental Crust (marshmallow vs. marshmallow) slam together they both want to float on top. So as they crash together they push each other up. This causes very high mountains like the Himalayas.

12 Strike slip faults simply slide past each other, but rocks never slide easily. They are rough and don t like to slide past each other. Every once in a while the rocks hold on until they break then the energy is released in an Earthquake The San Andreas Fault in California is a good example

13 Other than a funny name a dip slip fault is actually the kind of land you live on. In a dip slip area the faults run parallel to each other. Some faults push up, some push down, and you get high areas called horsts and low areas called grabens. In Utah the mountains were built by faults that lift up. They are a high place or horst, and the valleys get left behind, this is the graben.

14 There are a few different kinds of volcanoes. Cinder Cones Shield Volcanoes Stratovolcanoes Super Volcanoes

15 A cinder cone is a small volcano that erupts only once (usually). They usually don t spit out any magma, but just heave up really hot rocks into a cone shaped hill with a little crater on top.

16 Shield Volcanoes are huge mountains. These mountains are not steep at all. In fact most shield volcancoes have such gentle slopes that you barely even notice that you are on a mountain at all. The Hawaiian Volcanoes are all shield volcanoes. They get their name from the fact that from a distance they look like a shield laying on the ground.

17 Strato volcanoes are some of the prettiest mountains in the world. These are usually very steep and are easy to spot because they are beautifully cone shaped and have smooth sides.

18 Super volcanoes are strato volcanoes that get very large. These volcanoes are hard to spot after they explode because they usually leave such a big hole (caldera) that you can not tell that a mountain was ever there. Yellowstone is an example of this. The Caldera is nearly 20 miles wide. Crater Lake in Oregon is another example it is about 5-7 miles wide.

19 A Shield volcano has lava that is very thin. The lava simply oozes out of the hole at the top of the volcano and leaks down the side. Any gasses in the lava can get out easily. There is very little pressure and the volcano just does its thing. You could even walk up to the edge and look at the lava (if you don t mind the heat) Imagine blowing air through a straw into a glass of water. The air gets out easily. Strato Volcanoes have thick heavy lava. The lava does not flow very well and gasses get trapped in the melted rock. The pressure builds up on an enormous scale and the mountain explodes. Imagine blowing air through a straw into a glass of honey. The air would not get out very easily. You do not want to walk up to the edge of a stratovolcano when it is about to erupt because it would be the last thing you ever do, and they would never find the body.

20 Kilauea is the name of the active volcano in Hawaii. Kilauea has been erupting since If you are careful you can walk right up to the edge of the volcano, or even fly in a helicopter inside and be just fine.

21 The lava from Kilauea flows down the side of the volcano into the sea. Here it hardens into rock adding more land to Hawaii. Each of the Hawaiian islands was built this same way. Currently the big island of Hawaii is the only one that is still an active volcano, but there are many more. As the Pacific Plate moves the islands move away from the magma, are worn down by the sea, and eventually disappear.

22 As long as you don t get in the way of the Lava you will be just fine while visiting the volcanoes in Hawaii. When the eruption first started in the 1980s some people were hurt, and a few houses were burned by the lava, but most people were just fine.

23 A strato volcano has thick lava and lots of gas inside trying to get out. This causes huge amounts of pressure. When the volcano finally pops, thousands or even millions can be killed in many different ways. This is why you don t want to be anywhere near a strato volcano when it goes off.

24 In the spring of 1980 people in Washington started to notice that one of the mountains was growing and bulging out on the side. Scientists began to warn people that the volcano might be about to erupt. Sure enough, in May, 1980 the mountain exploded,

25 The first way Mt. St. Helens could have killed you was the shock wave. A shock wave is given off by any explosion, you usually hear it as a pop, but really powerful ones can hit your body like an enormous baseball bat. This shock wave and the shaking of the ground from the explosion would make things fall down, so you might be crushed by your falling house.

26 Of course the lava could burn you to death, but ash from a volcano can kill you too. It can be very hot, and it can bury you like a snowstorm from #(!!. Volcanic ash is actually very similar to tiny glass chips, so breathing it can do serious damage to your throat and lungs. The longest word in the English language is the name for a sickness that comes from breathing volcanic dust, the word is pneumonoultramicroscopicsilic ovolcanoconiosis

27 Many strato volcanoes are very tall and have snow on their peaks When the volcano erupts and suddenly lava comes out the snow melts almost instantly. The water mixes with dirt and you get a huge river of mud that can destroy towns, wreck bridges, and foul up lakes, rivers, and streams, as well as kill people. Sometimes the water has been heated by the lava, and can be very hot.

28 A volcano shoots hot ash and rock into the sky. Eventually it falls back down to earth Every once in a while it falls down along the mountain and races down at speeds of mph. The hot rock, gas, and ash is usually degrees. This flow buries towns and no one caught in the flow survives.

29 In the next few slides I will show you some famous volcanoes and explain what kind they are and whether or not you should be scared of them.

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37 As we have seen already Earthquakes happen when something stops the plates from moving. Eventually whatever stopped it from moving breaks, or lets go, and the plate moves to where it wants to be and the ground shakes like crazy. In the amount of time I have been up here talking there have been thousands of Earthquakes around the world. There have even been a few within a few miles of us. Why didn t we feel them?

38 The Richter scale is used to judge how strong earthquakes are. 1-3 on the Richter scale are called Microquakes, there are thousands everyday all over the world. A human would never feel them, but sensitive equipment can measure them. An earthquake that gets a 3 on the Richter scale is just about to the point where you can feel it, if you are sitting very still in a quiet room. Earthquakes are recorded using a seismograph.

39 A 4 pointer is strong enough that people will feel it and take notice. If you are out playing, you probably wouldn t feel it, and it probably wouldn t wake you up in the middle of the night. A 5 point earthquake is strong enough to start making pictures fall off of walls, crack plaster, maybe tip over unstable piles of junk. Very poorly built structures might be damaged. A 6 point Earthquake is strong enough to start causing damage to any structure. Most newer buildings will show cracks, but stay intact. Brick and masonry buildings might have some parts fall down. Poorly built buildings might collapse.

40 A seven point Earthquake (like the one in Earthquake Terror). Will cause damage to all buildings. Well built buildings will not collapse, but will be cracked and damaged. Poorly built buildings will collapse, people will probably die. Bridges might collapse, and roads will be impassible. Many fires will be caused by broken gas lines. An eight pointer will destroy most structures. The ground may actually rift open in huge cracks. Land might be heaved up or pushed down permanently. Damage to roads, highways, and other infrastructure will be major. Many people will be killed.

41 Only a few nine point earthquakes have ever been recorded. The damage would be catastrophic. Every building would be demolished. People hundreds or even thousands of miles away would experience damage. Thousands, or even millions of people could die. If near the ocean, killer tsunamis would radiate out around the world, and things would be really really bad!

42 Many scientists claim that Utah is at risk for a 6-7 point earthquake. If that happened there would be plenty of damage and many people would be hurt. You don t really need to worry too much though. As long as you know some basic Earthquake safety tips you will be just fine, scared yes, but just fine.

43 There are currently no active volcanoes in the state of Utah. We are not really close enough to a subduction zone or a hot spot. However there are a few semi-active volcanoes in Southern Idaho, that (if they ever erupted) would probably make life interesting, but not kill anyone around here. Scientists do worry about the Yellowstone Super Volcano though. If that went off, anywhere in Utah would not be a very safe place, but don t worry, scientists would be able to warn us months or even years ahead if Yellowstone once again became dangerous.

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