These systems of fissures that make up a rift zone allow this to happen more easily.

This volcanic activity has been along two rift zones, the southwest and east.

Due to stretching forces, the development of two or more rift zones is common.

Caldera development stops, and the rift zones become more inactive.

Lateral eruptions are typical at rift zones where a volcano is breaking apart.

It also coincides with a marked southward widening of the rift zone.

A prominent rift zone extends to the west.

A second rift zone probably extended to the east but has been buried by younger volcanoes.

The basins also display evidence of crustal thinning below the rift zone.

Observations show that both the north and south rift zones lack sediment cover, indicating recent activity.