The figure on the right is a schematic representation of the initial phase of continental breakup under the conditions of homogenous tension. Coarse, immature alluvial and fluvial deposits accumulate on its flanks. A rift system can be seen as a string of connected triple junctions or connected hot spots. The rifting process continues on two of the three arms.
Third arm becomes a failed rift called an aulacogen.
As the crust breaks due to the uplift and extension, blocks fall down along the normal faults creating a rift valley. Progressive spreading forms a wide, rift graben. Typical sediments are coarse immature alluvial debris and fluvial deposits. Small lakes with lacustrine shales, limestones and evaporites may form in the middle of the structure. Vulcanism is alkaline and peralkaline.