Great Rift Valley, Ethiopia8.8N 39.9E
The tan terrain dominating this image is part of an Ethiopian section of the Great Rift Valley. There is a green, vegetated stretch on the left side, near the center of the valley, where water is present.
A rift valley is a linear-shaped lowland between highlands or mountain ranges created by the action of a geologic rift or fault. This action is manifest as crustal extension, a spreading apart of the surface which is subsequently further deepened by the forces of erosion.
When the tensional forces are strong enough to cause the plate to split apart it will do so such that a center block will drop down relative to its flanking blocks. This creates the nearly parallel steeply dipping walls.
As this process continues the valley gets wider and wider until it becomes a large basin that fills with sediment (the tan terrain here) from the rift walls and the surrounding area. The area visible here, part of the East African Rift Zone, is still active today.