 Occasionally, fissure eruptions associated with rift zones can actually evolve into new vents along the volcanic edifice, generating lava flows lasting for months or longer.These lava flows add surface materials to the slopes of the volcano, extending the slopes outward in a general flattening of the morphology of the flank.The extensional character of these events can contribute to flank instability and mass wasting events where whole sections of the volcanic edifice can collapse along rift zone boundaries.