What is PLATE TECTONICS?

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1 What is PLATE TECTONICS? It s the theory that states: The surface of the Earth is not fixed and eternal, but it is in constant everchanging motion. If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle. 1

2 Alfred Wegener and the Continental Drift hypothesis.. A German meteorologist, Alfred Wegener, believed that the continents were once connected as one large super continent called. PANGAEA What does this word mean? ALL LAND And then there were two Pangaea originally broke into two large land masses connected by the Tethys Sea. Pangaea 200 million yrs ago.. These two land masses were known as: Laurasia Gondwana 2

3 Continental Drifting!! Is that possible?? Because of continental drifting, the continents broke apart and moved slowly to their present day location. How did this occur? This was caused possibly by the continents plowing through the ocean floor as the Earth spins on its axis. Watch as the continents moved throughout history to the present 3

4 What evidence did Wegener have to support his hypothesis? A) Fit of the continents - Scholars and cartographers as early as the 1500s saw that Africa appeared to tuck in neatly against the coasts of North and South America - In fact, all of the continents can be arranged to join with nearly no overlap or gaps. - Coincidence? Wegener thought not. What proof do we have of the continents were connected? B) Fossils of animals found in both Africa and S. America such as the mesosaurus Fossils of the same ancient plants found on different continents 4

5 More proof.. C) climate clues fossils of warmweather plants on islands of the Arctic ocean (even glacial deposits in S. America, Africa, and Australia!!) More proof.. D) rock clues- similar rock structures found on different continents 5

6 More proof.. The opossum is the only Marsupial" found on the continent of North America! He didn t swim here!! How is this picture proof the continents were once connected? Other proof..parts of the Appalachian Mt. chain resemble those found in Greenland 6

7 Continental Drift Video How Stuff Works: Continental Drift Love on the ROCKS 7

8 What s on your plate? Remember, the Earth s lithosphere is broken into sections called plates. Plates move around on top of the mantle like rafts There are two types of plates: Ocean plates - plates that are below the oceans Continental plates plates that are below the continents How many plates can you count!!! Which plates include only ocean floor? There are 15 plates!!!! 8

9 Study the map of Earth s plates in Figure 26. Notice the arrows that show the direction of plate movement. Now find the Nazca plate on the map. What direction is it moving? The Nazca plate is moving east Which direction is the S. American plate moving? What will happen as the plates continue to move? Pangaea Activity Directions - Use the evidences/clues on your handout (legend is at the bottom right of the page) to solve the puzzle to predict what PANGAEA looked liked over 200 million yrs ago. (in color!!) - CUT IT OUT NEATLY OR IT WILL BE HARD TO PUT ALL OF THE PIECES TOGETHER!!! 9

10 2 Types of Plates Ocean plates - plates below the oceans Continental plates - plates below the continents 10

11 Close-up of a tectonic plate Copy: Bellwork pg. 52 ISN (left side) Learning Target: I can explain the theory of seafloor spreading. Grab a notes guide on the blue cart and glue to pg. 65 ISN Questions are on the next slide. You have 5 minutes to answer them! 11

12 Bellwork pg. 64 ISN Write the answers only in complete sentences. 1. What does the theory of plate tectonics state? 2. What is the lithosphere? 3. What is the asthenosphere? 4. What is the connection between the two? 5. What are the two types of plates? 6. (True?/False?) As we go deeper down into the Earth, the temperature and pressure increases. Check your answers!!! (PANGAEA puzzle) 12

13 Pangaea Questions 1. What is the idea of Continental Drift? The idea of continental drift is that the continents were once joined together forming one big supercontinent called Pangaea, meaning all land and have since drifted to their present positions. 2. Which 2 continents have the most obvious fit of the coastlines? The eastern coastline of South America appears to fit like a puzzle with the western coast of Africa. 13

14 3. How were the fossil symbols and mountain belts helpful in deciding where to place the continents? Fossils of the same animal species were found on neighboring continents. Based on this evidence that supports continental drift, the fossil symbols and mountain belts (desert) were used to join the continents together like a puzzle. 4. Look where the fossil remains have been found. Why does this evidence support Wegener s theory about the existence of Pangaea the supercontinent? Fossils of the same animal species have been found on different continents. We know that animals can t swim across long spans of ocean, indicating the continents were once joined together. 14

15 5. Would a fossil of a fish be good evidence for continental drift? Why or why not? A fossil of a fish would NOT be good evidence for continental drift. A fish can swim, so if the continents were indeed once together, a fossil of a fish would not be relevant; only fossils of land animals would be. 6. Glossopteris was a fern that existed in a warm tropical environment 200 million years ago. Fossils of this plant have been found in what are now India, Antarctica, Australia, and Madagascar. What does that tell you about the climate and environment of what was then Gondwana? The climate of then Gondwana was warm if fossils of a warm weather plant was found in those existing areas. 15