long narrow fractures in the crust found along ocean floor or on land, from which lava flows out; often associated with spreading centers from which tectonic plates are diverging, such as the mid-Atlantic Ridge.
Elongate tapering ridges radiating from summit calderas and extend down volcano flanks into the sea. Fissures, pit craters, cinder and spatter cones, and small volcanic shield delineate the rift axis. Orientation of rift zones influenced by gravitational stresses and buttressing effects of pre-existing neighboring volcanoes (e.g., Kilauea volcano is buttressed against Mauna Loa). During rift or flank eruptions or intrusions, the summit usually deflates as magma moves into the rift zone accompanied by earthquake swarms map the magma movement.
A rift zone is a feature of some volcanoes, especially the shield volcanoes of Hawaii, in which a linear series of fissures in the volcanic edifice allows lava to be erupted from the volcano's flank instead of from its summit. For example, in the currently ongoing eruption of Kilauea lava is emitted continuously from the PuÊ»u Ê»ÅŒÊ»Å vent located in Kilauea's East Rift Zone roughly 15 km east of Kilauea Crater. Rift zones tend to extend for tens of kilometers radially outward from the volcanic summit; most Hawaiian volcanoes have two or sometimes three of them.