Thursday, March 10, 2011

The Incredible Crater Collapse

(The collapse of the Puʻu ʻŌʻō Crater in Hawaii. Courtesy of the USGS)

Last night, I attended the 1449th Meeting of the Geological Society of Washington , which meets at the Cosmos Club- the intellectual society founded by John Wesley Powell, one-armed Civil War vet and geologist extraordinaire. Preceding the evening's lectures, Dr. Roz Helz of the USGS (ret.) and the (The Hawaiian Volcano Observatory) brought forth an "informal communication" before the group. Her presentation highlighted the video above, which was recorded on March 5th by the HVO's extensive video monitoring system on several major volcanoes and vents, from Mauna Loa (the most voluminos mountain in the world) to Kilauea (one of the most active volcanoes in the world.) This particular video shows the latter, specifically an outlet called the Puʻu ʻŌʻō Crater. The time-lapse video shows from 4 AM to 11 PM, where runny basaltic lava poured out and hardened on the crater floor, only to collapse 377 feet into a hellish looking pit. I would have loved to hear a bit more explanation about how this happened, but my guess is that the magma plume that was rising underneath the crater subsided quickly, either because of changing pressure and temperature in the Earth's crust, or because the magma was diverted elsewhere. The crust of dried lava on top appears to keep accumulating puddles of lava from smaller side vents until the weight is too great. It is impressive how much steam and gas escapes from the crater once the top is broken.

It is a great illustration of the liquidy, syrup-like lava of basaltic volcanoes with their low viscosity. (Hawaii's volcanoes are fed by basaltic magma, which is low in thickening silica, unlike a stratovolcano like Mt. St. Helens.) According to Hawaiian tradition, the name for the Puʻu ʻŌʻō crater derives from the word for "digging stick." It was apparently, Pele, the goddess of volcanoes, who created these structures using the tip of her giant staff. I think all of us in tectonically stable areas can be glad that she didn't walk over our homes.


mountainbeltway said...

Hi James,
Good to meet you last night -- and thanks for posting this video. FYI, it was Roz Helz of the USGS was the one who delivered the informal communication.

James Anderson said...

Thanks for the tip Callan! I'll update the post accordingly.

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