What could possibly cause there to be patterns in these lakes?

	Lake Manasarowar looks like this along the shoreline. Photo courtesy of http://www.goldenbridge.net/Tibet-LakeManasarovar.htm.

Well, we know from the Detailed Information page in the Datasystem for this image that it was taken on January 13, 1997 at about 6:54 am Greenwich Mean Time.

	The shoreline of Raksas Tal, like Manasarowar, has naturally occurring ridges and hummocks. Photo courtesy of August Gansser from Throne of the Gods.

Since Tibet is in the Northern Hemisphere, it is winter in January; so it could be ice or snow. When we saw the ground photographs (we don't know what time of year these were taken), we thought that it could be that the lakes were very shallow and we were seeing sediments that made up an uneven bottom showing through.

Since the lakes are fed by glaciers and they don’t drain out to any rivers, their volumes and depths would vary from year to year. They would depend upon the amount of snow that fell and melted, the amount of water that evaporated during the dry season and the amount of sediment that was delivered with the runoff of snowmelt. The whole area has been marked by the activity of alpine glaciers. One of the signs that glaciers leave behind when they melt is piles of unsorted rocky debris called glacial till. The photo below shows hummocks of galcial till in the area between the lakes.

		Hummocks of glacial till in the region between Manasarowar and Lake Raksas; the mounds are made of material that has been scraped up by a glacier and deposited where the glacier melted. Photo courtesy of August Gansser from Throne of the Gods.

One of the atlas maps we looked at even showed the lakes joined as one but we read that the Hindu and Buddhist traditions have recognized two distinct lakes for centuries. So, as you can see we had conflicting data to work with.

We came across the picture below while looking for possible explanations for the patterns in the lakes. The formations are called "patterned ground". Patterned ground occurs in places where the ground goes through repeated cycles of freezing and thawing. Searching the web turned up many similar photographs and the names of a couple of specialists in patterned ground. Since we were at a dead end with our resources, we decided to try asking an expert if they would help us out.

	These sorted circles of gravel and stones occur naturally on an island north of Norway. Just how the circles were produced is still debated though their appearance is associated with recurrent freeze and thaw cycles. Photo courtesy of Professor Bernard Hallet, Quarternary Research Center, University of Washington, Seattle.

We e-mailed our request to an expert who was kind enough to look at our images. The response we got teaches a few things about how to come up with a hypothesis (or how to make an educated guess) and what makes an expert an expert.

What we might have figured out on our own, but didn't:

The white color of the patterns is similar to the color of the snow on the surrounding mountains and (probably frozen) rivers and lakes.

The patterns are built up on the eastern ends of the lakes; like something blown to the side by wind. In fact, the winter winds here are very strong and they are out of the west, which could cause just exactly what we can see here.

What only an expert would know:

The patterns look very much like jumbled sea or lake ice. A cracked pattern forms when slabs of ice, pushed by wind, jam up against one another then drifting snow can accumulate at the junctions. The accumulation of drifting snow at cracks and junctions in the lake ice is something you can see in early winter in parts of Alaska in years when there is only a little snow. The patternless ice on the eastern margin is probably that way because it froze massively after the evacuation of all its slabs of mobile ice.

It was suggested that we could verify the hypothesis that the patterns are caused by ice and snow by looking at ground photos taken in the winter or satellite images taken in the summer. We'll have to go looking for some.

Our thanks to Professor Brad Werner of Scripps Institute of Oceanography and his graduate student Lawrence Plug.

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