What is a Rift Valley?
A rift valley is a geographic feature caused when one arm of a triple junction between tectonic plates “fails” (i.e., stops spreading) and leaves a remnant canyon-like structure. Unlike canyons, which are formed by river erosion, rift valleys, formed through plate tectonics, are much larger. The largest rift valley in the world is the Great Rift Valley in East Africa, 6,000 km (3,700 mi) in length, extending from Syria in the north to Mozambique in the far south. There are rift valleys on other planets, too: Valles Marineris, on Mars, at 4,000 km (2,5000 mi) long, 200 km (125 mi) wide and up to 7 km (4.3 mi) deep, is the largest known crevice in the solar system. All of the world’s largest freshwater lakes are in rift valleys, including Lake Baikal in Russia (the world’s largest lake by volume, holding 20% of the world’s fresh water), Lake Tanganyika in Africa (second largest lake), Lake Superior in the United States (third largest), and a number of others. The world’s largest subglaci
