Rift
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In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems.
Volcano-tectonic landforms connected to rifting on Reykjanes Peninsula, Iceland: faults, fissures, elongated volcanoes of subglacial origin, postglacial lava fields
Graben
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In geology, a graben is a depressed block of the crust of a planet or moon, bordered by parallel normal faults.
Infrared-enhanced satellite image of a graben in the Afar Depression
The Newark Basin, an early Mesozoic half-graben
Rima Ariadaeus on the Moon is thought to be a graben. The lack of erosion on the Moon makes its structure with two parallel faults and the sunken block in between particularly obvious.