Monday, September 13, 2010

The ice melts

Image courtesy of Earth Sciences and Image Analysis Laboratory, NASA Johnson Space Center. ISS015-E-7109

This is too gorgeous for words, so I won't waste many. The image here was taken in early May of 2007 and shows Yellowstone Lake in the mid-to-late stages of its spring thaw. Some of these cracks are enormous - the lake is about 20 miles from the tip of the Southeast Arm (bottom center), where the Yellowstone River enters, to the outlet at Fishing Bridge (center top). And as you can judge from the color, it's really more slush than ice. The lake may have been frozen three feet deep in January and the water never does warm up, even in a hot August, so the thaw is a protracted process.

Here's a view just one week earlier, on the last day of April:


Cranberry Necklace said...

In the second image in the very center of the lake is a dark spot. I took it to be an island, but the first image has a much larger spot in the same location. It must be an area of open water that gets larger as the thaw progresses. But it is unusual for a lake to thaw from the center, isn't it? Is there perhaps a hot spot under that part of the lake? There is another spot just a bit to the southwest which seems similar, though it is next to the shore. Knowing of Yellowstone's volcanism, and that lakes often form in craters, I wonder if those two spots are known volcanic vents.

Scott Hanley said...

No, that dark spot is Frank Island. You can see it in this map here. It's heavily forested and there must have been no snow in the trees at the time of the photo, but that's true of most of the shoreline, too, so I'm not sure why it's that much darker.

I was really surprised at the darker "shadow" on the east side of Frank, Dot, and Stevenson Island. It also exists along the western shore (especially Plover Point below the Flat Mountain Arm), but not on the eastern shore. It looks like the slushy ice is being blown eastward and piling up on the east side of the lake.