b. c. d. e. Earthâs crust is thicker than the mantle. Earthâs crust is part of the asthenosphere and equivalent to it in composition. Earthâs crust is part of the mantle and forms the upper part of it. * Earthâs crust is less dense than the mantle 15. Roughly how many tectonic plates move around on the surface of the Earth? a. none; they donât mover around on the surface, they mostly move up and down. b. 4 or 5, depending on size c. * 10 or 12 d. about 50 e. more than 300 16. What characteristics of lithospheric plates distinguish them from deeper Earth materials? a. They are partly molten b. They behave in a more plastic manner c. * They are rigid. d. They consist entirely of basalt e. They are generally overlain by continental crust. 17. What keeps the Appalachians standing as a mountain range even though they have been continuously eroding since they formed hundreds of millions of years ago? a. They are actually becoming lower by the amount that material is eroded off the top. b. They are again being pushed up by collision between the Atlantic Ocean floor and the continent. c. The subduction zone at the Atlantic continental margin is now pushing ocean floor under them to keep them up. d. * As material is eroded off the range, it floats higher on the mantle rocks below. e. The continents below a depth of 5 to 10 kilometers are molten basalt and they float on that. 18. What is the basis for the âscientific method?â a. Scientists come up with a theory and then seek out data to prove that it is correct. b. Scientists experiment with data to observe the data that they like best. c. Scientists try to discredit ideas proposed by others. d. Scientists prove their hypotheses with data that demonstrates their correctness. e. * Scientists test their hypotheses with new observations and experiments 19. Why do many oceanic volcanoes occur as long lines of volcanoes that are active at only one end? a. * The lithosphere moves over a stable hotspot in the mantle.