 Perhaps the best example of this is Mauna Loa, which in Hawaiian means "long mountain", 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.The internal extensional forces and isostatic loading generated by intruding magma volumes (either associated with the magma chamber or subsequent dyke and sill formation extending outward from that chamber), in conjunction with accumulation of erupted materials, contribute to the mass and slope of the forming edifice.