The crust sections move very slowly. The ocean floor plates may slide under continental plates, sinking deep into the earth causing crustal deformation. The crust of the earth, including both the continents and the ocean basins, consist of separate plates that ride on a denser layer of the earth. The slow movement of material within this dense layer results from heat flowing from the deep interior and the action of gravitational forces. Volcanoes form over unusually hot centers in the interior of the earth, along separating plate boundaries, or near descending plates.
Earthquakes also occur along plate boundaries.
Both of these can have a significant impact upon human activities. Explore the Alaskan economy before and after the 1964 earthquake. Reshaping the Earth's Surface 1. Rocks formed by internal processes are unstable at the earth's surface and are susceptible to processes of weathering and erosion. The net effects of the weathering and erosion processes are soil formation, and a general leveling of the land forms.