Rift zones are narrow areas along the oceanic trenches where hot solid mantle rocks rise upward to replace the material that has shifted horizontally.

A rift zone sometimes occurs in some volcanoes, more so in the shield volcanoes. It is made up of a linear series of fissures in the volcanic edifice. Lava can erupt from this, let us call it volcanic flank, instead of it's summit. Rift zones tend to extend for dozens of kilometers. Volcanoes have an elongated shape because of the repeated eruptions from these rift zones.