Chapter 14 Earth's Interior

19. As rocks experience increased pressure with depth, P waves in general will _______ as they migrate through them. A. travel faster B. travel slower C. travel at the same velocity D. rapidly die out

A. Seismic wave velocities depend on the elasticity, rigidity, and density of materials. These properties depend on the composition, physical state, and compactness of the atomic structure of the material.

15. The crust is typically thickest beneath A. high mountain ranges and plateaus on the continents. B. ocean-spreading centers. C. continental interiors like the Great Plains in North America. D. passive margins of continents where topography is very flat.

A. The thickest continental crust on Earth lies beneath the Tibetan plateau, Himalayan mountains, and portions of the Andes mountains.

13. Which layer of the Earth experiences the most rapid increase in temperature with increasing depth? A. lithosphere B. asthenosphere C. mantle D. liquid outer core

A. lithosphere

24. The P-wave shadow zone is caused by the way the Earth's core A. refracts the seismic waves. B. reflects the seismic waves. C. absorbs the P waves. D. blocks the P waves.

A. refracts the seismic waves.

5. Continental crust has an overall composition corresponding closely to that of A. ultramafic. B. mafic. C. felsic to intermediate. D. peridotite.

C. Continental crust is very heterogeneous in composition. Nevertheless, its average composition is felsic to intermediate.

1. Earth's core has a radius that is about __________ of the Earth's radius. A. 1/8 B. 1/4 C. 1/2 D. 3/4

C. Earth's core is about one-half the radius of the planet.

14. On which boundary in the Earth's interior does the greatest change in composition occur? A. lithosphere-asthenosphere boundary B. crust-mantle boundary C. mantle-core boundary D. boundary between the outer and inner core

C. The mantle-core boundary is marked by the most significant change in composition.

8. The highest density component of the Earth is A. the mantle. B. continental crust. C. the core. D. the whole Earth

C. The metallic core has the highest density.

3. The likely composition of the upper mantle is A. felsic. B. mafic. C. ultramafic. D. carbon (diamonds).

C. Ultramafic or peridotite.

6. The lithosphere is a __________ layer, as opposed to the asthenosphere. A. plastic B. fluid C. weak D. rigid

D. The lithosphere is thought to be a rigid layer that rests on a plastic, weak asthenosphere.

17. The Earth's core is inferred to be composed of mostly iron because A. iron is naturally very abundant. B. most meteorites representing the interstellar matter from which the planets formed are rich in iron. C. iron is very dense, so its presence in the core would account for the Earth's average density. D. all of the above.

D. all of the above.

26. Earth's tectonic plates are located in the A. core, where their movement is driven by intense heat and pressure. B. mantle, where their movement is driven by convection. C. lithosphere, where their movement is driven by gravity. D. atmosphere, where their movement is driven by the prevailing westerlies.

D. atmosphere, where their movement is driven by the prevailing westerlies.

25. As the lithosphere cools slowly by the conduction of heat, it becomes A. less dense and rises. B. soft and weak. C. denser and rises. D. denser and subsides.

D. denser and subsides.

4. Which of the following constitutes the rigid, outer layer of Earth's tectonic plates? A. asthenosphere B. lithosphere C. crust D. mantle

B. Earth's tectonics plates are large fragments of the lithosphere, a rigid layer consisting of the crust and uppermost mantle.

7. The inference that Earth's outer core is liquid is supported by the observation that A. P waves do not pass through it. B. S waves do not pass through it. C. P waves travel more rapidly through it. D. S waves travel more slowly through it.

B. S waves do not pass through the outer core.

21. The Moho discontinuity between the crust and the mantle, was first detected from A. the abrupt decrease in seismic velocities as they cross the discontinuity. B. the abrupt increase in seismic velocities as they cross the discontinuity. C. the S-wave shadow zone through which S waves do not pass. D. the observation that no earthquakes occur below the Moho.

B. The Moho was first detected by an abrupt increase in seismic wave velocities due to the change from lower-density crustal rocks to the more dense ultramafic rocks within the mantle.

11. As opposed to the lithosphere, the asthenosphere is a ________ layer. A. brittle B. weak C. molten D. rigid

B. The asthenosphere is thought to be a weak, plastic zone within the upper mantle that may be partially melted.

2. The thickness of Earth's tectonic plates is A. the same on the continents as under the oceans. B. at its thinnest under the oceans. C. at its thinnest in the continents. D. completely unknown.

B.The ocean basins exist on Earth because the ocean crust is thinner and denser than the continental crust. Therefore, the ocean crust sits lower.