Rift zone

[2] The accumulated lava of repeated eruptions from rift zones along with the endogenous growth created by magma intrusions causes these volcanoes to have an elongated shape.

[3] Perhaps the best example of this is Mauna Loa, which in Hawaiian means "long mountain",[4] and which features two very well defined rift zones extending tens of kilometers outward from the central vent.

Rift zones are characterized by the close grouping of intrusive dykes and extrusive fissures extending outward along a relatively narrow band from the area of a central vent.

[2][5] Following the path of least resistance, subsequent magmatic dykes form along and within these initial cracks, causing additional stresses to be imparted to the local materials of the edifice, which in turn generate new rifts for the magma to flow towards.

[1] However, where the flanks of a volcano may be supported on one side by the presence of a pre-existing feature, or burdened with various planes of weakness, rift zone formation promulgates according to down-slope pull of gravity.