An observatory set up underwater 300 miles off the Oregon coast in the Northwest Pacific has captured for the first time the process of sea-floor spreading in amazing detail. Axial Volcano rises 0.7 miles from the sea floor and its peak lies only 0.85 miles below the ocean’s surface making it within easier reach than some other underwater volcanoes. It also erupts approximately once every ten years. Observing volcanoes underwater is actually easier in some respects, as the earth’s oceanic crust is thinner (around 4 miles compared to around 20 miles in continental crust) so the magma chamber is closer to the surface and can be more easily monitored. Luckily the observation site was completed just months before the volcano erupted and began recording information in those months. Up to 1000 earthquake tremors a day were measured in the precise area in the months leading up to the eruption which itself lasted over a month. This has now settled down to only about 20 per day. Volcanologists were extremely interested in observing the direction of the lava flow and how the rock formed. The two previous eruptions had shown the lava flow travelling south of the volcano but the latest one sent the lava flow north. This had been predicted by the area where the seismic activity had been observed. They were also interested in the formation of the Caldera. This is caused by the magma chamber emptying creating a void which can no longer support the weight of the rock above and so collapses creating the ring structure often seen in volcanic structures.
Scientists are hopeful that these observations can be used to better predict volcanic eruptions and the structure of the rocks formed afterwards not just underwater but also on land.