Bermuda consists of a group of over 120 rocky islands covered by sandy soils. The exposed parts of the islands consist mostly of limestone. In this respect they are totally different from the original hard-rock volcanic islands that first formed Bermuda. This change is a result of the activities of marine organisms that colonized the original volcanic rock. This group of oceanic islands has always been far from any continental landmass. It arose about 110 million years ago due to volcanic activity along the Atlantic mid-oceanic ridge. Because Bermuda rides on the North American plate, it has been moved by plate tectonics 1,800 kilometers (1,118 miles) to the west, to lie in the western Atlantic Ocean.
The living sea turtles are air-breathing reptiles that evolved from freshwater turtles during the age of dinosaurs. They represent a single evolutionary radiation that is adapted for life in the ocean. Their fossil record extends back at least one hundred and ten million years, but today all sea turtle species are threatened with extinction.
Nearly all sea turtles found in Bermuda waters are immature. Bermuda appears to be a place where young sea turtles grow up separate from adult animals. Nearly all that grow up here will return to the Caribbean Sea before they mature.