Britannica Sources used in this answer

How do rift volcanoes form between diverging tectonic plates?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

tectonic basins and rift valleys Escarpments of the Great Rift Valley rising above the plain north of Samburu Game Preserve, central Kenya. Beisa oryxes graze in the foreground.

Rift volcanoes form as a direct result of the divergence of tectonic plates. As these plates move apart, the Earth's crust is thinned and stretched, causing it to fracture along steeply dipping cracks.12

This process creates a gap that allows hot material from the asthenosphere to rise to shallow depths. As this magma ascends through the fractures, it can erupt at the surface, forming volcanoes. In oceanic settings, such as the Mid-Atlantic Ridge, this activity is typically effusive and produces basaltic eruptions that build shield volcanoes.2134

In continental settings, such as the East African Rift System, the formation of rift volcanoes can be more complex. The upwelling of hot material often creates large domes, causing the lithosphere to bulge and stretch. Because the rising magma may assimilate continental crust during its ascent, these volcanoes can exhibit a wider range of rock types and more explosive characteristics than those found along oceanic ridges.21