Half-graben

In the rift basin, warm mantle material wells up, melting the crust and frequently triggering the eruption of volcanoes.

Rift border faults with lengths over 10 kilometres (6.2 mi) are separated by relay ramp structures.

The first is "escarpment margin" sedimentation, found along the major border faults bounding the half graben, where the deepest part of the basin meets the highest rift-shoulder mountains.

Other material is transported across or along the basin to the deep water parts of a rift lake along the escarpment margin.

The "axial margins" at the ends of basins often include low-gradient ramps where major rivers enter the basin, building deltas and form currents within a rift lake that can carry sediment from one end to the other.

Between adjacent half grabens there will be "accommodation zones" that may include local extension, compression or strike-slip faulting.

[6] Although sediments arrive primarily from the unfaulted side of the half-graben, some erosion takes place on the fault escarpment of the main border fault, and this produces characteristic alluvial fans where confined channels emerge from the escarpment.

As the rift valley aged, extensive deformation developed on both sides of the lake, converting them into asymmetric full grabens.