Kilauea erupts when magma (molten rock) rises from deep inside the earth and accumulates inside a reservoir approximately four kilometers underneath the summit. Sensitive instruments can actually detect the mountain swelling as pressure inside the reservoir builds. Eventually the pressure forces the magma to the surface and there is an eruption.
Although people usually think of lava spewing from the tops of volcanoes, many of Kilauea's eruptions, including the current one, have taken place along its flanks. Before an eruption on Kilauea's flanks, magma travels underground laterally (sideways) from the reservoir rather than straight up. These protrusions of magma extending from the reservoir are called dikes. Scientists theorize that as the magma pushes through the ground, pressure causes the surrounding rocks to crack. Magma rushes in to fill these cracks, and the dike becomes longer. When the magma reaches the surface, fissures open up, and lava pours out.
The system of cracks created by the underground movement of magma is called a rift zone. Kilauea has two major rift zones the Southwest Rift Zone and the East Rift Zone. The East Rift Zone is by far the longer of the two and is currently the most active. It extends 55 kilometers from the summit to the shore then continues another 75 kilometers underwater.
Kilauea is currently erupting from the Pu'u O'o vent on the East Rift Zone about 20 kilometers from the summit. The Pu'u O'O vent is shown in the picture on the left. Lava is spewing from the summit and moving away in a lava channel.
In the past, eruptions have occurred all along the rift zone, including the submarine portion. Puna Ridge is built from these underwater eruptions.
|Contour map of the Puna Ridge. The last part of the subaerial rift zone is seen on the left in white and the Puna Ridge continues underwater. Blues represent the deepest water.|
The primary goal of our cruise is to get a better understanding of the Puna Ridge. This information will help us to understand how magma moves within Kilauea volcano, where eruptions are likely to occur, and how the eruptions will act. It will also help us to understand the formation of other oceanic islands, submarine volcanoes and mid-ocean ridges.