Africa

Africa, like other continents, "floats" on a plastic layer of the earth's upper mantle called the asthenosphere. The overlying rigid crust or lithosphere, as it is known, can be as thick as 150 mi (240 km) or under 10 mi (16 km), depending on location. The continent of Africa sits on the African plate, a section of the earth's crust bounded by mid-oceanic ridges in the Atlantic and Indian Oceans. The entire plate is creeping slowly toward the northwest at a rate of about 0.75 in (2 cm) per year.

The African plate is also spreading or moving outward in all directions, and therefore Africa is growing in size. Geologists say that sometime in the next 50 million years, East Africa will split off from the rest of the continent along the East African rift which stretches 4,000 miles (6,400 km) from the Red Sea in the north to Mozambique in the south.