Okefenokee is a 396,000 acre bog inside a huge, saucer-shaped depression that was once part of the ocean floor. Peat deposits, up to 15 feet thick, cover much of the swamp floor. These deposits are so unstable in spots that one can cause trees and surrounding bushes to tremble by stomping the surface. In fact, Okefenokee is a European rendition of the Indian words meaning "land of the trembling earth."