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Warm-Up • Grab your mastery folder and the papers from the back table. • Begin figuring out your level of mastery from the pre-test using your test answer sheet and the mastery paper (on the back table). • Some students received partial credit on a question. You will just turn the percentage into a decimal. So if you earned a 70% on a question, that is a .7 that you will use to divide by the total number of questions. • There are calculators on the small group table if you need a calculator. • SWBAT explain the physical processes associated with tectonic plate movement Continental Drift & Plate Tectonics Geology Rocks! NAME___________________________ Alfred Wegener (Weg-en-er) was a meteorologist and explorer. In 1912, he came up with the idea that the continents did not always look like they do today. 1 Rocks Climate Fossils Wegener’s idea came from studying ____________ , _______________ , and the ___________________ of all of today’s continents. He found that the fossils and mountains in South Africa matched the fossils and mountains in Argentina. How could that be? There is an ocean between South Africa and Argentina! He also found fossils of tropical plants in places like Greenland. How could a tropical plant live in snowy Greenland!? 2 Pangaea – 200 Million Years Ago Seven Continents - Today The mystery was puzzling. That’s when Wegener came up with the theory that the continents did not always look like they look today. He said that they used to be one big supercontinent. He named this large continent Pangaea. Pangaea is a Greek word that means “all lands.” 3 Wegener said that it took millions of years for the seven continents we know today to drift to where they are now. But, he did not know how the continents drifted. Continents are huge! How could a big, heavy continent move that far? Because Wegener could not prove his theory, other scientists did not believe him. He had some evidence, but he needed to figure out how the continents moved if he was going to get others to believe his theory. 4 Wegener never figured out how the continents moved, but his work led the way for other scientists. These scientists used new technology to collect information. They measured the ocean floor, recorded earthquakes, and studied the Earth’s magnetic fields. They used the things they learned to form a theory on how continents could move. This new theory was called plate tectonics. The theory of plate tectonics explains how the Earth’s plates move and change. The Earth is made of layers, very much like an egg. The top layer of the Earth is called the crust. The theory of plate tectonics says that the top layer of the Earth is broken up into many plates, or thin sections, that move and change. 5 plates super-heated rock Under the plates, there is another layer of rock called the mantle. The mantle has two parts. The first part is a rock layer. The second part is made of super-heated rock. The plates float on this super-heated rock, but they don’t float like rafts float in a swimming pool. The melted rock is very thick like silly putty. So, the plates drift very slowly. 6 In 50 to 100 million years, the Earth could look like this! Scientists believe the Earth’s continents have divided and drifted back together many times in Earth’s history. Although you cannot see it with your eyes, the plates are still moving today. It can take a whole year for a plate to move just a few centimeters. That means that in your whole lifetime, our continent will only move about 2 feet. However, in millions of years, the Earth will look very different than it does today. 7 What is Plate Tectonics? • Plate tectonics is the theory that explains the formation, movement and subduction of Earth’s plates What happens when the plates move? • No plate can budge without affecting the other plates surrounding it. • As the plates move, they collide pull apart, or grind past each other producing changes in the Earth’s surface. What kind of Changes? Volcanoes! Mountain ranges! Earthquakes! Sea-trenches! Plate Boundaries • The edges of the different plates meet at lines called Plate Boundaries • At the border of plate boundaries are FAULTS—cracks in the Earth’s crust • There are three different types of boundaries that occur because of their different movement Types of Boundaries • Transform Boundaries • Divergent Boundaries • Convergent Boundaries Transform Boundaries • Along transform boundaries crust isn’t created or destroyed • At a transform boundary the two plates slip past each other Transform Boundaries • Why do earthquakes shake California? • The state straddles two plates that are moving past each other like trains on opposite tracks. The plate boundary is marked by a zone of active faults—breaks in the rock and ground surface caused by plate movements. Transform Boundaries • The most famous of these is the 1200-km (750-mi) long San Andreas Fault. The San Andreas fault is a transform fault, a kind common on the sea floor but rarely found on land. Divergent Boundaries • The place where two plates move apart—or diverge—is called a divergent boundary • Most divergent boundaries occur at the mid-ocean ridge—so crust is forming • When divergent boundaries occur on land, a rift valley is formed Rift valley Convergent Boundaries • The place where two plate boundaries come together or converge is called a convergent boundary • A collision is when two continental plates hit each other—the density of the crust determines which plate goes under the other one • Ex. – The Himalayan Mountains Convergent Boundaries - Subduction • One tectonic plate sinks under the other • Basalt is what oceanic crust is made out of. It is more dense than continental crust. Use this fact to explain the movement of these plates around the convergent boundary. • Ex: Japan