In Case You Haven't Seen It: Shock-wave from Volcanic Blast at Papua New Guinea's Tavurvur Volcano

This has been making the rounds on Facebook and Google+, but just in case you missed it, have a look at the shock wave from an eruption at Papua New Guinea's Tavurvur (or Rabaul) volcano. The footage was captured by an Australian couple, Phil and Linda McNamara. The shock wave is astounding.

Tavurvur is a small stratovolcano on the island of New Britain that has been highly active and dangerous. It nearly destroyed the town of Rabaul in 1994 and killed more than 500 people during an eruption in 1937. It is part of a larger (8x14 km) caldera that formed about 7,000 years ago.

Shock waves are nothing new, but good video images are. The cable television show Mythbusters has gotten a lot of mileage showing the effects of shock waves. In geology, I've been showing a satellite photograph from the eruption of Mt. St. Helens in 1980 to my classes for years that shows the shock-wave from that eruption. But a static shot doesn't capture the dynamic nature of such explosions. Closer to home, an explosive shock-wave from a 1996 rock fall in Yosemite Valley destroyed hundreds of trees in the area around Happy Isles.

It's astounding stuff.

Geologic Change in Yosemite: Remembering the Happy Isles Slide of 1996

I was looking for something else in the massive pile of old slides and photographs at the department today, and ran across a pair of photographs of taken a few weeks after the Happy Isles Rockfall of 1996, one of the more damaging historical mass wasting events in Yosemite Valley. The pictures recall a flurry of posts last spring about the Ahwiyah Rock slide near Half Dome. The 1996 event killed one person and severely injured another, destroyed a food stand, and damaged the Happy Isles Nature Center.

The rock involved in the event was a slab of exfoliated granitic rock roughly the size of a football field that broke off from the top of the cliff near Glacier Point, slid for several hundred feet and then fell 1,800 feet, hitting the floor of the valley at a speed of something over 200 mph. The rocks exploded on impact generating an airblast that toppled 1000+ trees. U.C. Berkeley has an excellent analysis of the slide here, and formal article from the GSA Bulletin can be found here.

Regrowth of trees and shrubs has obscured much of the damage, but the Happy Isles Nature Center has a nice exhibit and viewpoint; walk out the back door of the museum to find it. The slide was not the first in the area. Huge talus piles cling to slopes below the breakaway point, and a much larger prehistoric slide has been mapped beneath the thick forest. It forced the Merced River into a new channel, and contributed to the formation of the marshy area west of the campground.