Saturday, August 31, 2013

Japan's rumbling super volcano

Fun fact: The Sakurajima volcano that had a blowup a few weeks back, and the cities it dusted with ash, all sit within the Aira "super volcano" caldera, which covered much of Japan's southern half with immense pyroclastic flows and ashfalls around 22,000 years ago.

Photo courtesy of NASA, Public Domain
The caldera encompasses the rounded top of the bay, the Sakurajima island and mountain edifice, and the cities adjacent to the bay.

So, time to panic? Not by a long shot. We still simply do not understand what drives the behavior of the large caldera volcanoes. We don't know if Sakurajima's eruptions reduce pressure, or if they in some way help contribute to the stockpiling of the gas rich, crystallized magma that drive massive VEI-7 and 8 scale ash eruptions. Yellowstone has its unpredictable rises and falls, as does the Long Valley Caldera in California, and the smaller, but more vigorously active Campi Filigrei in Italy. That's to say nothing of a mysterious large area of swelling in South America under the region that has the highest known concentration of super volcanoes, as well as the rise of  the island of Iwo Jima, which has been lifted several hundred feet during the three-hundred year inflation of the submarine caldera it sits within.

But we are learning.

There are various sources of knowledge. We're learning to read the continual outgassing of these large and complex volcanic systems to get a better idea of what's happening chemically in the vast magma chambers and saturated rock that are the hearts of these monsters. We're using earthquakes and the differences in densities that affect their propagation through the Earth's crust to create ultrasound-like images of the deep, subterranean interiors. And the discovery of an exposed and neatly cross-sectioned fossil chamber in the Alps promises to give us a snapshot of the dynamic center of a dead giant, and the processes that shaped its life.

No comments: