Plate Tectonics

1. a boundary in which two plates move apart, resulting in upwelling of material from the mantle to create new seafloor.
4. deep canyonlike structure
6. a hypothesis, first proposed in the 1960s by Harry Hess, which suggested that new oceanic crust is produced at the crests of mid-ocean ridges, which are the sites of divergence.
9. a chain of volcanic islands generally located a few hundred km from a trench where there is active subduction of one oceanic plate beneath another.
11. were formed when India “rammed” into Asia.
13. an elongated depression
15. a hypothesis which suggested that all present continents once existed as a single supercontinent.
18. is the primary driving force for movement of tectonic plates.
19. supercontinent containing all of the existing continents.
20. older, denser portion of oceanic lithosphere descend into mantle at a rate equal to seafloor production.

2. wrote a book titled The Origin of Continents and Oceans that outline his continental drift hypothesis.
3. processes that deform Earth’s crust to create major structural features, such as mountains, continents, and ocean basins.
5. a well-tested theory proposing that Earth’s outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself.
7. linear zone of irregular topography on the deep-ocean floor that follows transform faults and their inactive extensions.
8. elevated areas of the seafloor characterized by high heat flow and volcanism.
10. occurs when igneous rocks melt over a temp range.
12. a boundary in which two plates move together resulting in oceanic lithosphere being thrust beneath an overriding plate, eventually to be reabsorbed into the mantle; could also create a mountain system.
14. a boundary in which two plates slide past one another without creating or destroying lithosphere.
16. a narrow, elongated depression of the seafloor
17. a continuous elevated zone on the floor of all the major ocean basins and varying in width from 500 to 5,000km 300-3,000 miles.