Plate Tectonics

Mesosaurus

Mesosaurus

CHAPTER 10: PLATE TECTONICS VOCABULARY & QUESTIONS

Vocabulary
1. Continental Drift- Wegener’s hypothesis that all continents were once in a single large landmass that broke apart about 200 million years ago and drifted slowly to their current positions.
2. Pangaea- a large ancient landmass that was composed of all the continents joined together
3. Seafloor Spreading- Hess’s theory that new seafloor is formed when magma is forced upward toward the surface at a mid-ocean ridge
4. Plate Tectonics- theory that Earth’s crust and upper mantle are broken into plates that float and move around on a plastic-like layer of mantle
5. Plate- a large section of Earth’s oceanic or continental crust and rigid upper mantle that moves around on the astenosphere
6. Lithosphere- rigid layer of earth about 100 km thick, made of the crust and a part of the upper mantle.
7. Asthenosphere- plastic-like layer of earth on which the lithospheric plates float and move around.

Diagrahm of Sea Floor Spreading

Diagrahm of Sea Floor Spreading

8. Convection Current- current in Earth’s mantle that transfers heat in Earth’s interior and is the driving force for plate tectonics.

Questions
1.

Earth's Plates

Earth's Plates

Who came up with the concept of continental drift?
Alfred Weneger
2. How do Mesosaurus fossils support the past existence of Pangaea?
Because they have been found on more than one continent which means they lived on both continents when they were joined.
3. How do Glossopteris fossils support the idea of continental drift?
Because they have been found on five continents.
4. How were climate clues used to support continental drift?
Because fossils of plants found in warmer climates were found on islands in the Arctic Ocean, proving that those lands must have been somewhere with a warmer climate at one time. He also found glacial deposits in Africa, India, South America, and Australia, proving that those lands had once been frozen.
5. How were rock clues used to support continental drift?
Rocks on the eastern coast of South America were similar to those of the west African coast, which supports the idea that the continents were connected in the past.
6. Why wasn’t the hypothesis of continental drift accepted by scientists?
It could not be proven.
7. What is a mid-ocean ridge?

Glossopteris Fossil

Glossopteris Fossil

An area where new ocean floor is formed when lava erupts through the cracks in Earth’s crust.
8. Who suggested the idea of seafloor spreading?
Harry Hess.
9. How does new seafloor form at mid-ocean ridges?
When lava rises to the surface and cools and forms new rock.
10. What happens to the age of the seafloor rock as you move further away from the ridges?
It increases.
11. What is significant about the magnetism of the rock found on the seafloor?
Because iron-bearing rocks can record Earth’s magnetic field direction. If Earth’s magnetic field reverses, so will the direction of the movement of rocks
12. What happens at a divergent boundary?

The Glomar Challenger

The Glomar Challenger

The Earth’s plates move apart.
13. What happens at a convergent boundary?
The Earth’s plates move toward each other and collide.
14. What is subduction?
When a denser plate collides with a less dense plate and sinks under it into the mantle.
15. What happens when to continental landmasses collide?
Mountain ranges form.
16. What happens at a transform boundary?
Earthquakes.
17. How can convection currents be used to explain how the tectonic plates move?
Because the hotter magma deeper underground is forced up, moving the crust upward but then cools and sinks back down.
18. What 3 features are caused by plate tectonics?
Mountains, valleys, and volcanoes.

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