Calderas collapse as magma flows into rifts

Recent caldera collapses show the importance of distant volcanic rift zones Major magma drainage from volcanoes causes the collapse of volcanic edifices, forming calderas that can be both many kilometers wide and hundreds of meters deep. Many calderas form during major explosive eruptions, when magma erupts from fractures on ring faults that bound calderas. However, the most recent caldera-forming events at Kīlauea Volcano, Hawai'ei, in 2018 ( 1 ) and at Bárðarbunga, Iceland, in 2014–2015 ( 2 ) formed by a different mechanism. Both events were gradual caldera collapses that occurred as magma flowed over long distances into rifts far away from volcano summits. The caldera ring faults associated with collapse only began to move after a major magma withdrawal into a rift zone.