Geology 12 Name:______
Ms. Pushie Date:______
Plate Tectonics ~ Chapter 19 Assignment
1. What two theories combined to form the theory of plate tectonics? Continental Drift and Seafloor Spreading.
2. What is tectonics? The study of the origin and arrangement of the broad structural features of the Earth’s surface.
3. Give some examples of tectonics. Folds, faults, mountain belts, continents, earthquake belts etc
4. What is the basic idea behind plate tectonics? The Earth’s surface is divided into a few large, thick plates that move slowly and change in size.
5. What occurs at plate boundaries? Intense geologic activity occurs at plate boundaries, where plates move away rom one another, past one another or toward one another.
6. How many large plates are there? How many small plates are there? 8 large plates, 12 small plates.
7. When was the concept of plate tectonics born? Who initially proposed the theory? 1960, Alfred Wegener
Continental Drift
8. How long has the theory of continental drift been around? 130 years
9. What are some pieces of evidence for continental drift?
- Puzzle pieces
- Paleozoic rock fossils including plant glossopteris, reptile fossils, climate zones and rocks and glaciation pattern
10. What is Pangea? When Pangea divided into two main pieces, what were they called? The giant super-continent when all landmasses were together. Laurasia – North and Gondwanaland – South
11. Please draw the diagrams in figure19.2
12. Explain 4 reasons why Wegeners theory was not initially accepted.
- Reptiles could have crossed land bridges
- Plants could have spread by wind or ocean currents,
- Pole wandering could have caused climate zones and
- Force required to move the continents was too great to be explained
Paleomagnetism
13. Hows is the Earth’s magnetic field recorded? Magnetite in cooling basaltic flows act like tiny compass needles, preserving a record of Earth’s magnetic field when it cools below the Curie Point.
14. What is the Curie Point? What is Paleomagnetism?
15. Recent evidence supporting Continental Drift?
- Puzzle pieces of continental slopes of the continents
- Ice age spill-over pushing boulders from one continent to the other Ex: Africa onto South America
Seafloor Spreading
16. Who proposed the theory of seafloor spreading? Harry Hess
17. What does the seafloor spread away from? What is the mechanism behind seafloor spreading? Mid Oceanic Ridges and the deep mantle convection (movement of the magma coming form the core.)
18. Explain subduction.
19. Explain convection
20. The interaction between the moving seafloor rock and the stationary rock can cause Benioff zones of Earthquakes associated with trenches. It can also produce andesitic volcanoes, which forms volcanoes either on the edge of a continent or in an island arc.
21. Sea floor age – Where do we find the youngest seafloor? Where do we find the oldest sea-floor? The youngest is at the mid ocean ridges and the oldest at the edges of the trenches.
Plate and Plate Motion
22. Define a plate in the geologic context. What three different plate compositions are possible? A large mobile slab of rock that is part of the Earth’s surface. Plates can be composed of oceanic rock, oceanic and continental rock or continental rock (small plates only).
23. What is the lithosphere and what two layers is it composed of? The lithosphere is located under the crust and it is composed of the crust and the upper mantle.
24. Where is the asthenosphere located and what layer is it composed of? How does the asthenosphere help the plates move? The asthenosphere is part of the mantle and it lubricates the lithosphere, thus allowing it to move.
25. Describe plate movement. Plates move as a unit. The interior of a plate is inactive and the plate boundaries are highly active.
26. How are plates defined and located? Plates are defined and located by mapping narrow belts of earthquakes, volcanoes and mountain belts.
27. There are three general types of plate boundaries, please name and explain them.
Divergent
Convergent
Transform boundaries
How do we know that plates move? Pg 471-484 (skipping this section)
The attractiveness of Plate Tectonics
-In a full double spaced page, summarize this information using your own words.
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