There are more than 200 craters on the flat flanks of Marsabit, a volcano that rises like a green island about 3,200 feet above the Chalbi Desert in northern Kenya. This mighty shield volcano lies on the furthest edge of the East African Rift, and is around five million years old. The small cones on its ridge emerged about 500,000 years ago, when Marsabit began spitting lava and ash again after a long dormant period, allowing molten material to break through the old volcano's slopes in many different places.
The volcano's rock acts like a sponge. It stores the water that falls from the sky during the short rainy season in dry northern Kenya, making agriculture possible on the land.
Photo credit: Bernhard Edmaier