This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Friday, October 22, 2010

Volcanoes and atom bombs

Photo of Matua volcano, Siberia, taken by NASA astronauts
Detonation of a thermobaric (fuel-air) bomb by the Russians.
Believed to be the largest of its kind ever detonated.
The New York times recently had a photo documentary of development of the atomic bomb. The photo below is of a "fuel-air bomb", often called a "vacuum bomb". This type of explosive uses oxygen from the surrounding air to increase the duration, and destructiveness, of the shock waves/fireball. They were first developed by the Germans during WWII, and are in use by modern military and in guerilla warfare (1993 World Trade Center bombing, 2002 Bali bombings).

Some volcanoes have eruptions that are "explosive" enough to produce shock waves.  These were first recognized by Perret during explosive eruptions of Vesuvius in 1906, and were later observed and analyzed quantitatively at Ngauruhoe, New Zealand (Nairn, I.A., Nature 259 (5540, pp. 190-192, 1976). On June 12, 2010, NASA astronauts were able to capture the photo at the left of an eruption of Matua volcano, Siberia.  You can't see the shock wave directly, but can see the hole that it punched through the cloud deck.  The rising ash plume has also pushed up a layer of moist air forming a pileus "cap cloud".  A pyroclastic flow is visible at the base of the column, descending toward 5 o'clock on the flank of the volcano.  Volcanologists use some of the same basic concepts about shock waves that were developed to analyze shocks from atomic bombs, and although we talk about the energy released in eruptions in terms of "kilotons" or "megatons". For example, I analyzed the energetics of the lateral blast at Mount St. Helens in 1980, and concluded that about 24 megatons of energy was released during the blast (Kieffer, S.W., Nature, 291, 568-570, 1981).

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