The Great Rift Valley cuts a swath down the eastern side of the African continent. Slicing across 4,500 miles from the Dead Sea in the north to Mozambique in the south, it forms the largest visible rift on earth, although a few larger rifts lie under the waters of the Atlantic, Pacific and Indian oceans. Shifting tectonic plates formed the Great Rift about 30 million years ago when the plates of Africa and Eurasia crashed together, then pulled apart and caused huge landslides to empty rock from the earth's surface deep inside its crust.

Volcanos have rearranged strata of various minerals into new forms and deep craters all along the Great Rift. Wind, rain, and sun have shaped the faces of 6,600-foot cliffs. Water has collected in the valley to form bodies of water like Lake Natron, which hosts hundreds of thousands of flamingos, and Lake Eyasi, which forms the eastern boundary of land occupied by the Eastern Hadza people. The rift also contains one of the world's largest Volcanos, Mt. Kilimanjaro, and the only active volcano in Tanzania, Mt. Lengai. Millions of years of erosion have made the surrounding volcanic soil oddly fertile.

The valley supports a profusion of animal life unequaled anywhere else in the world. Huge herds of migrating wildebeest, up to a million strong, roam and stampede along with hundreds of thousands of zebra, Thomson's and Grant's gazelle, and other hoofed animals. Predators eat well when migration brings these animals nearby, but wild cats and scavengers must otherwise work hard to subsist on small mammals and birds.

The Great Rift still lives. Many of its Volcanos smolder, and some are still erupting. Earthquakes occasionally shake the savannas; the Dead Sea widens a few feet each year. Eventually, in the next few million years, the rift could deepen further, fill with sea water, and cut off the eastern section of Africa to make it a separate landmass. Until then, the Great Rift Valley should continue to offer excellent wildlife viewing and a close look at the inner workings of the planet.