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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
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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
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