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

Wednesday, October 20, 2010

Hail, hail, the ?'s all here!

Hail damage to a windshield.

Hail causes nearly $1 billion damage in the US each year, mainly to crops, but buildings, vehicles, and people are not immune to hail damage.  On April 30, 1988, a hailstorm in India is believed to have killed 246 people and 1600 animals. More intriguingly, it is believed that a huge hail storm may have killed at least 200 nomads in the Himalayas during the 9th century. The nomads are believed to have been Hindu pilgrims, and more than 600 bodies may remain buried in the ice.  Their skeletal remains are being disgorged from ice high in the mountains.  The skulls of these people showed short, deep cracks caused by round objects about the size of cricket balls.  This event may have inspired a traditional song of the Himalayan women that describes a goddess "so enraged at outsiders who defiled her mountain sanctuary that she rained death upon them by flinging hailstones 'hard as iron.' " A hailstone the size of a baseball falls at something like 100 mph, about the velocity of the throw of a major league pitcher. Hail can damage airplanes because they fly at speeds of 200-300 mph, and on April 4, 1977 a DC-9 crashed in Georgia when both engines of the plane ingested hail.  The plane crashed an burned, killing two crew members, 60 of 81 passengers, and 8 on the ground. Hail does not reach even higher speeds because of several factors: the turbulence of the atmosphere prevents a straight-line path from cloud to ground, and hailstones also bump each other and raindrops.  Hailstones deform during their descent because of friction with the atmosphere, and cannot be modeled as perfect spheres.  Small hailstones are commonly nearly spherical, but large hailstones are almost never spherical.

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