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

Monday, August 22, 2011

Beautiful waves over the (formerly beautiful) Aral Sea

Clouds over the (turquoise) Aral Sea
NASA image MODIS on Aqua satellite, March 12, 2009

In the image above a series of waves spreads out over the Aral Sea, with the (left) boundary of the clouds conforming closely to the shape of the western shore of the Aral. As discussed in this NASA Earth Observatory post, clouds usually form when air rises over a mountain or other topographic high.  Air cools as it rises, and moisture can condense out into clouds.  When air flows down the other side of the mountain, it warms up and moisture evaporates, limiting clouds near the high axes of the mountains.

Before and after as labelled. From Wiki.
What could be causing the clouds around a sea? The most likely explanation is related to the fact that the Aral sea has been drying up, so that the water lies now in the deeper parts of the previously much larger basin. The Aral is a classic example of a sea affected by, and affecting, multiple nations: Kazakhastan, Uzbekistan, Turkmenistan, Tajikistan, Afghanistan, and the Soviet Union. At one time, the Aral was one of the four largest lakes in the world, with more than 1500 islands (the name means "Sea of Islands"). In the 1960's the rivers feeding it were diverted by irrigation projects, primarily in the Soviet Union, causing it to decline to 1/10 of its original size by 2010.

Because the lake has been shrinking, it is likely that the now-dry parts of the basin to the west are higher than the lake surface and causing the formation of the clouds.  Changes in wind speed as the wind came across dry land to the west, where it would have been slowed by vegetation, and flowed east over the smoother lake, where it could accelerate may have contributed to formation of the waves over the lake.

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