An anomalous magma chamber has been observed at 8–11 km depth beneath the upper east rift zone of one of the world’s most active volcanoes – Kilauea, Hawaii.

Using seismic data, a group of volcanologists led by Paul Okubo of U.S. Geological Survey developed a 3D model to determine the size, depth and composition of the reservoir.

The crustal magma reservoir is several kilometers in diameter and located at a depth of 8-11 km. It is composed of so-called magma mush – a mixture of 90-percent rock and 10-percent magma.

“This reservoir could have supplied the magma that intruded into the deep section of the east rift zone and caused its rapid expansion following the 1975 M7.2 Kalapana earthquake,” Mr Okubo and his co-authors said in a paper published in the journal Geology.

The reservoir below Kilauea is similar to those widely observed beneath volcanoes located at mid-ocean ridges.

“Understanding these magma bodies are a high priority because of the hazard posed by the volcano,” said co-author Prof Falk Amelung of the University of Miami.

“This study is the first geophysical observation that large magma chambers exist in the deep oceanic crust below,” said first author Dr Guoqing Lin, also from the University of Miami.

______

Guoqing Lin et al. Seismic evidence for a crustal magma reservoir beneath the upper east rift zone of Kilauea volcano, Hawaii. Geology, published online January 10, 2014; doi: 10.1130/G35001.1