 The addition of these magmatic materials usually contributes to the further rifting of the slope, in addition to generating fissure eruptions from those dykes that reach the surface.It is the grouping of these fissures, and the dykes that feed them, that serves to delineate where and whether a rift zone is to be defined.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.