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01. A \"mystery\" in our understanding of plate tectonics has been, until recent

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Question

01. A "mystery" in our understanding of plate tectonics has been, until recently, the nature of the power source capable of moving the plates and the continents embedded within them. Recent evidence indicates the power source to be

1. the readjustment of the surface to the continual shrinking of the whole Earth.

2. newly triggered by H-bomb tests in the Pacific in the mid-1950s.

3. convection currents within the Earth's mantle, causing movement of the plates.

4. the continual vibration from earthquakes and volcanoes causing slow movement of the continents toward the equator under the influence of centrifugal force.

5. the action of ocean currents dragging along the seafloor, causing movement of the seafloor and the continents.

02. Which of the following statements does NOT correctly describe subduction zones?

1. They are sites where lithosphere plates are diverging or pulling apart.

2. They are belts of deep-focus earthquakes.

3. They are zones where the old seafloor descends into the crust and mantle.

4. They are marked by the presence of deepsea trenches.

03. Plate tectonic theory is considered a unifying theory because it

1. current explanation for such Earth processes as volcanism and earthquakes.

2. a common belief of a broad spectrum of geologists from different disciplines.

3. is the only theory explaining earth dynamics that hasn

Explanation / Answer

01. convection currents within the Earth's mantle, causing movement of the

plates.
02. They are sites where lithosphere plates are diverging or pulling apart.
03. current explanation for such Earth processes as volcanism and

earthquakes.
04. convergent
05. the circum-Pacific belt.
06. hydrothermal alteration and contact metamorphism
07. the object at sea level because the distance to the center of Earth is

least from this elevation.
08. the crust-mantle boundary.
09. is destroyed as fast as it is created.
10. tensional
11. thermal convection cells in the asthenosphere and mantle.
12. convergent
13. divergent
14. Only C is true.
15. A, B, and C are true.
16. midocean rifts.
17. continental and oceanic crust only.
18. Alfred Wegener, 1912
19. continental crust could move through ocean crust.
20.
21. how Earth