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21. What was the primary reason why Alfred Wegener’s theory of continental drift
* He had no mechanism for moving continental crust through strong basaltic oceanic
22. The “Ring of Fire” refers to what and where is it?
* the ring of active volcanoes surrounding the Pacific Ocean.
23. Convergent plate boundaries are especially noted for which two types of natural
* earthquakes and volcanoes +/- tsunami
24. In the line of arc volcanoes, like the Cascades of Washington and Oregon, over an
active subduction zone, a series of events leads to the magmas that erupt at the surface.
What magma forms first and where and how does it form?
* Basalt magma forms at (just above) the subduction zone below the volcano, when water
formed by dehydration of hydrous minerals in the descending slab causes melting of
the mantle peridotite above.
25. How is the magma formed that feeds the volcanoes in Hawaii?
* The lithosphere carrying Hawaii slowly moves over a mantle hotspot causing melting
to form basalt magma..
Multiple Choice Questions
1. What direction is the Pacific Plate currently moving, based on the chain of
Hawaiian islands with only the easternmost island active?
to the northeast
* to the northwest
to the southeast
to the southwest
It is not moving; the chain of islands is not related to the active one.
2. Before people understood plate tectonics, what evidence led some scientists to
believe in continental drift?
Rocks on the ocean floor are oldest in the center, becoming progressively younger
towards each continent.
Rocks on the continents can be traced through the ocean floor to the other side.
Anthropologists have found human carvings in Africa that match those in Brazil.
Glaciers near the mouth of the Amazon River in Brazil carried distinctive rocks
into South Africa, demonstrating that those countries were once connected.
* Ages of bedrock formations match across the Atlantic Ocean