Geotimes
Geophenomena

Glacial valley avalanche in Russia
China's air needs a chimney sweep

Glacial valley avalanche in Russia

An avalanche of mud, trees, rocks and boulders of ice washed through the Caucasus Mountains on Sept. 20 at 9 p.m., following a partial collapse of the Kolka Glacier in the southern Russian Republic of North Ossetia-Alania near the Georgia border. The Russian Federation estimated that the glacier dropped 22 million tons of ice down the mountainside. The fall destroyed a village and killed at least 17 people.

The outflow of mud and debris measured 200 meters wide and 10 to 100 meters thick. The flow traveled 11 kilometers down the alpine valley, destroying the village of Karmadon, blocking the Karmadon Gorge and damming some of the rivers that feed into it. Two villages along the gorge were under surveillance as flood waters backed up along the choked rivers. On Sept. 25, a first round of explosives intended to break up the avalanche flow was unsuccessful in reducing flood waters lapping through the village of Gornaya Saniba. But officials planned to continue using explosives.

As of Oct. 4, rescue workers had found 17 bodies and knew of 124 people still missing, including Russian actor Sergei Bodrov, members of his film crew and 20 employees of the North Ossetia parliament’s staff and administration.

Speculation varies on why the glacier suddenly failed. After evaluating the site on Sept. 24, the Minister of Emergencies, Sergei Shoigu, reported to the United Nations that the glacier’s slide might have resulted from volcanic activity. However, glaciologist Dmitry Petrakov of Moscow State University told U.S. News and World Report that the disaster may have started when a small, overhanging glacier at the peak of Mount Dzhimarai-Khokh fell into the Kolka Glacier. Adding to the theories, Bruce Molnia of the U.S. Geological Survey suggests that increased precipitation in recent months may have triggered an outburst flood from a glacial lake. “For a fluidized debris flow like this you need a huge volume of water,” he says. Increased precipitation could have raised the volume of such a lake until the lake walls burst, mobilizing the glacial ice, he adds.

Christina Reed


back to top


China's air needs a chimney sweep

Soot provides a cooling counter to the heat-trapping effect of greenhouse gases, but its polluting effects make the air a danger to health. Now, a study shows that the cooling effects also take their toll. The study, published in the Sept. 27 Science, shows that large amounts of black carbon particles, or soot, are contributing to significant changes in precipitation and temperature in China and soot is at least partially responsible for increased flooding in southern China and droughts in northern China over recent decades.

A typical hazy day near Lin An, China. Black carbon emanates from a small brick factory. Photo courtesy of Science magazine.

Indeed, scientists have observed what they deem the largest change in precipitation trends since A.D. 950. Black carbon particles act like a giant shaded window, absorbing sunlight that heats the surrounding air but blocking sunlight from reaching the ground and thus cooling the surface. The heated air makes the atmosphere unstable, creating convection, which forms clouds and brings rainfall. The increase in rising air and rainfall in southern China is countered by an increase in sinking air and drought in northern China. When air sinks, clouds and rain cannot form, creating dry conditions. This pattern alters atmospheric circulation and the hydrologic cycle as far away as Canada and Afghanistan.

Surabi Menon and Larissa Nazarenko of the NASA Goddard Institute for Space Studies and Columbia University, along with Goddard scientist James Hansen and Yunfeng Luo of the National Science Foundation of China, used aerosol data from 46 ground stations in China and Goddard’s climate computer model to investigate possible aerosol contributions to precipitation and temperature. They conducted four sets of computer simulations to monitor the effects of soot on the hydrologic cycle over India and China. The team observed a direct correlation between the effects of increased soot over southern China and recent floods and drought.

“If our interpretation is correct, then reducing the amount of black carbon or soot may help diminish the intensity of floods in the south and droughts in the northern areas of China, in addition to having human health benefits,” Hansen says.

In China, sources of soot include industrial pollution, diesel traffic, outdoor fires and household burning. Soot is largely generated by cooking and heating, which, unlike in many developed nations, are done with wood, field residue, cow dung and coal (Geotimes, November 2001).

In a companion “Perspectives” article in the same issue of Science, Michael Bergin and William Chameides of the Georgia Institute of Technology’s School of Earth and Atmospheric Sciences explore policy implications of this climate study. Because black carbon particles have relatively short atmospheric lifetimes, they write, successful control efforts could curb the effects of soot in a matter of months or years. Efforts to control soot may also bring immediate human health benefits, because the small soot particles cause respiratory distress when trapped in the lungs.

“These health impacts could make it politically much easier for policy-makers to enact the kinds of controls needed,” Bergin says. “The control strategy could provide a double-whammy by increasing the health of both human beings and the environment.”


Meg Rudolph
Geotimes contributing writer


back to top

Geotimes Home | AGI Home | Information Services | Geoscience Education | Public Policy | Programs | Publications | Careers

© 2014 American Geological Institute. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the express written consent of the American Geological Institute is expressly prohibited. For all electronic copyright requests, visit: http://www.copyright.com/ccc/do/showConfigurator?WT.mc_id=PubLink