and with tremendous force (Figure10.49). Scientists believe that air gets trapped under
the falling rocks and acts as a cushion that keeps the rock from slowing down. Landslides
and avalanches can move as fast as 200 to 300 km/hour (Figure10.50).
Figure 10.49: Landslides are called rock slides by geologists. ( 49 )Landslides are exceptionally destructive. They can bury everything in their path, including
entire villages. Some landslides have created lakes when the rocky material dams a river or
stream. Often homes are destroyed as hillsides collapse. If a landslide flows into a lake or
bay, they can trigger a tsunami. In July of 1958, a landslide of 30.6 cubic meters of rock fell
from 914m up on a steep slope at the end of Lituya Bay in Alaska (Figure10.51). As that
large volume of rock suddenly pushed away all the water, a 524m tsunami was formed. The
tsunami produced by the landslide knocked down all the trees and vegetation surrounding
the bay. In the area directly opposite the landslide, trees at elevations higher than the