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Plate Tectonics, Earthquakes, and Landforms
Transcript of Plate Tectonics, Earthquakes, and Landforms
These intense vibrations are what we know as an Earthquake. Oceanic crust is made from basaltic rocks. Because of this, it is much denser and heavier than Continental crust. It is also denser because it not only has air pressure pushing down on it, but water water pressure also. Oceanic crust lies under the ocean and is usually about 5-7 kilometers thick. Along with being denser than Continental crust, it is also thinner. The Theory of Continental Drift The Theory of Continental Drift suggests that movement of Earth's continents are all relative to each other. It is the gradual movement of the continents through Geological Time. Once, all of the continents were joined together into one big "super continent" (as most scientists refer to it as). This was called Pangaea. Earthquakes What is it? Trenches An earthquake is a sudden, violent shaking of the ground as a result of the movement of the Earth's crust. A trench is a long sunken formation along the ocean floor. Remember This? Yes! That's right! It is the trench from Finding Nemo! They are underwater valleys that are located and formed at subduction zones. Trenches are the deepest points on the Earth's surface. Remember back to the Big Idea of Science, (physical and chemical principles are unchanging and drive both the gradual and rapid changes in the Earth System).
Earthquakes are an example of a rapid change
in the Earth system because they happen through an extremely short period of time compared to geological time. Convection in the mantle moves Earth's tectonic plates. This causes the oceanic plate to collide with a continental plate or another oceanic plate. The denser, older plate is forced below the less dense plate and Voila! A trench has been formed! Where do they occur? Earthquakes occur on plate boundaries known as fault lines. The focus of the earthquake is the point where pressure is released and this is directly above the epicenter. Scientists still can't be 100% sure exactly where an earthquake will take place, but almost all fault lines are mapped. Electromagnetic fields surrounding fault lines will emit light just before an earthquake and can be used to predict when it will take place. Cities that are built near fault lines are at a high risk for earthquakes. Because of this high risk, buildings are designed to be strong enough to withstand earthquakes in those areas. How Are They Caused? Volcanoes This type of plate boundary is called a divergent plate boundary because convection in the mantle causes the plates to pull apart and magma to rise up to the surface. Now you must be asking yourself, what's the difference between lava and magma? Lava is magma that has reached the Earth's surface. Over time, magma that flows from the mantle through a crack between a divergent plate boundary cools and forms rocks. These rocks add up and form........VOLCANOES! There are Three Types of Volcanoes... 1) Shield Volcanoes
-have curved slopes that rise upward
-shaped like a shield
-made of liquid lava
-have small eruptions; not as explosive
-eject a steady stream of molten lava How Does a Volcanic Eruption Take Place? Volcanic eruptions occur when pressure forces magma from the chamber to the main vent. Scientists can use seismology to predict when a volcano will erupt, and seismology is the study of vibrations in the Earth. Mount Kilauea is the world's most active volcano, and it is a shield volcano. The Discovery of Continental Drift The theory of Continental Drift was discovered by a scientist named Alfred Wegener in 1912. Back then no one believed his theory, and they all thought that everything had been the same since the creation of continents. However, Alfred Wegener had proof to show his theory accurate. Some continents have the same fossils on them as others continents across the ocean. Also, all the continents match up like a big puzzle. This proves that at one point all the continents had been connected. All these continents fit together Also, the fossils found on them are identical What's Earth Made of? Earth is made up of four layers:
1. The deepest layer, the inner core, is solid and created from earth's denser materials. It mostly consists of iron and nickle, and scientists use a hydrogen gas gun to discover the core reaches 4000 to 7000 degrees centigrade depending on depth.
2. The outer core is made up mainly of the same material as the inner core. However, due to less pressure it's liquid instead of solid. Also, the outer core reaches scorching temperatures just as the inner core.
3. The largest layer would be the mantle. It's mostly made up of solid rock that reaches 3000 kilometers deep, but there's also molten rock that is melted due to the core's heat. Convection occurs in this layer, and causes the movement of tectonic plates.
4. The crust is the smallest layer of earth, and also the layer we live on! The crust is broken into thirteen pieces, which are the tectonic plates. Seven of these are the "main plates" and each one has a name. There is the Eurasion plate, North American plate, South American plate, Pacific Plate, African plate, Australian plate, and the Antarctic plate. Human vs Geological Time As you saw in the Big Idea of Science, chemical and physical properties are unchanging. For example, millions of years ago all the continents were together in one big super continent known as Pangea. Throughout millions of years all the plates moved and shifted until we arrived to today's continents.
Back in prehistorical times when dinosaurs still roamed the earth the planet was already shifting. We see major changes in the continent placement through similar fossils on other continents. The creatures who made those fossils couldn't have swam the distance between these continents, meaning they must have been at one point connected. In millions of years, the Atlantic Ocean will be larger. This change in the ocean's sizes are occurring every day, since each plate moves two centimeters a year. Two centimeters, which doesn't seem like a lot to you. However, after millions of years those centimeters add up and create whole new oceans and continents. What About Changes Happening Present Day? Remember back to January 12, 2010. One of the world's most destructive earthquake struck Haiti, measuring a 7.00 on the Richter scale. Haiti lies on the Caribbean Plate and the North American Plate (notice that it is on a transform plate boundary). After a while, these plates built up pressure and suddenly slipped, causing the Haiti earthquake. Volcanoes occur mostly on destructive and constructive plate boundaries where tectonic plates are pulled apart. As you can see, earthquakes can cause so much destruction in just a matter of minutes. In Haiti's case, their earthquake caused millions of lives to be destroyed and 8-12 million dollars of damage. Mid- Ocean Ridges What are Mid ocean Ridges? Mid ocean ridges are a really long chain of volcanic mountains in the ocean that erupt regularly. They erupt because of the fumes from magma rising up from the mantle. They are located along plate boundaries and have average depth of about 2,500 meters. Mid ocean ridges are known as the spreading center because they are on divergent plates. Divergent means the spreading (or dividing) between two plates. Over time, parts of the land form started to drift apart and form the continents that we have today all with the help of Plate Tectonics! How are they formed? Mid ocean ridges are formed from plate boundaries. When two plates collide with each other, it causes a form of magma and underground pressure to create a pool of lava. Some of these pools can grow and be up to 60,000 kilometers long. Because of this, more than 90% of the earths mountains are under the ocean. Some of the tallest mountains are under water too, even taller than Mt. Everest. Each year the plates separate 2 centimeters, making the depth bigger and bigger. Yellow Arrow: Shows how the America's
will shift and then connect with the east
coast of Asia.
Orange Arrow: Shows how the Atlantic Ocean will get bigger until there is no more Pacific ocean and only one huge Atlantic Ocean.
Blue Arrow: Shows how Africa will become connected with southern Europe and connect with Saudi Arabia also. Map of the Earth Millions of Years From now Hot Spots What are Hot Spots? Hot spots are formed when there is a weak part in the lithosphere that allows magma to break through. This is how Shield Volcanoes are formed, from tectonic plates located over hot spots. Hot spots have already been existent for over 100 million years. The state of Hawaii was formed from a line of hot spots in the Pacific ocean. Our Big Idea Of Science Our Big Idea of Science is, "Physical and Chemical Principles are unchanging and drive both gradual and rapid changes in the Earth System". What Does This Mean? The processes occurring ever since the Earth was formed are the same as the processes occurring now. Also, these same processes will occur in the future. "The Present is the Key to the Past" -James Hutton Oceanic Crust An example of one process that has been occurring since Earth was formed is Plate Tectonics... The world is covered in plates. These plates are made up of continental and oceanic crust. There are 13 total plates, but some would argue that there are only seven. These plates shift and move because of the convection that occurs in the mantle. There are many outcomes that occur due to plate tectonics. Some of these outcomes are Continental Drift, different kinds of landforms, and natural disasters. Principle of Uniformitarianism The principle of Uniformitarianism is based on the fact that all of the Earth's landforms are the result of processes that have operated in the past, in the present, and in the future. James Hutton (known as the father of geology in 1785) suggested this theory. Hutton's theory was, "the present is the key to the past". He described that catastrophic processes were not responsible for the landforms that exist on Earth. This idea is called catastrophism, and was very popular at this time. While Hutton claimed his beliefs, others had some of their own. Some thought that the landforms developed over long periods of time through slow geologic and geomorphic processes. Hutton claimed that it is highly unlikely that a sudden disaster would be held responsible for formation of certain landforms. Unlike catastrophism, the principle uniformitarianism is very consistent. Tectonic Plates There are thirteen (and seven main) tectonic plates that cover the Earth. These plates can vary in size and thickness, and float because of their composition. Tectonic plates are made from oceanic and continental crust. Rift Valleys Rift valleys are formed when there is sunken formation on land from a divergent plate boundary. After a while, this sunken piece of land can fill up with water, forming a pond. Each year, it gets bigger and fills up with more water and eventually you have an ocean. This is how the Atlantic ocean was formed. Plate tectonics are responsible for the formation of Rift valleys. The way that plate tectonics cause rift valleys is by two plate boundaries move apart. They will then be pulled by thin extensional forces. Then magma comes up from the mantle, cools, and fills in the gaps. As the plates pull apart the valley deepens and widens. They form over millions of years, this process is called Orogeny. Continents are a part of the tectonic plates that make up the crust of Earth. They move about 2cm a year because of Continental Drift. Fold Mountains The highest fold mountain is Mt. Everest, and it stands at a height of 8,850 meters. Tsunami A tsunami is normally caused by undersea earthquakes. Displacement of water above fault lines create ripples that turn into a wall of water that crosses the ocean extremely fast. This creates a massive wave that can cause massive damage along with it. This diagram shows how rift valleys work. If you look at the arrows you can you can see how the rift valleys form, and how they expand. This model will help show you the size of fold mountains, the materials that make up a fold mountain, and how they compare to other landforms. Three Types of Plate Boundaries There are three types of plate boundaries, convergent, divergent, and transform. Each type of boundary creates a different kind of landform. Some of these landforms are mountains, volcanoes, mid-ocean ridges, rift valleys, and even trenches. Plate boundaries can also cause certain natural disasters also. Fold mountains are formed when convergent plates collide. They buckle up and form mountains. This process formed the Himalayan mountains when India collided with Asia . 2) Cinder Cone Volcanoes
-have a steep hill with straight edges
-if it keeps spewing lava, it may form into a shield volcano
-made of explosive liquid lava
-very explosive 3) Composite Volcanoes (also known as a Stratovolcano)
-curved lower slopes and steep upper slopes
-made of layers of lava
-made of explosive debris As you can see, Plate Tectonics is a very important process that has been around since the beginning of the Earth. It causes rapid and gradual changes in the Earth's system such as the formation of landforms, earthquakes, and continental drift. We Hope You Enjoyed This Presentation! Plate Tectonics Created By: Anna Villamil, Liz Hawkins, Meghan West, Paige Sorentino, and Anthony DiGiamberardino