Monday, July 16, 2007

Lake Bonneville

Back when Puget Sound was covered with ice - the last time, at least - it was much wetter in Utah's Great Basin. The Great Basin was still a great basin, however, with no place for the water to get out. Lake Bonneville reached over 1000 feet in depth before spilling out it's north end into the Snake River valley. The Great Salt Lake is but a small remnant of this once much greater, and much fresher, body of water. The lake left several distinct shorelines and beaches at its margins - as seen in the benches on the hillslope in this picture (hazy due to brush fires).


Six weeks ago I was in New Orleans, not far from where the Mississippi enters the Gulf of Mexico. Almost 3900 miles upstream, in Yellowstone Park, the Firehole and Gibbon Rivers join to form the Madison River. The Madison joins the Jefferson and Gallatin Rivers in Three Forks, Montana, to form the Missouri River, which in turn joins the Mississippi at St. Louis. It's a long way from the hot springs of Yellowstone to the French Quarter.

Sunday, July 08, 2007

Yellowstone Lake

Some of my favorite gravel beaches are these barriers on Yellowstone Lake. I saw them first by accident about a dozen years ago - although my recollection is that the lake level was considerably higher. I believe on that trip, the beaches at the north end were almost submerged, whereas they seemed just the opposite this year. I'll have to see if I have some pictures from back then.

Although the lake is ultimately volcanic in origin - it fills a large part of the Yellowstone Caldera - these beaches are built of glacial sediments. The pictures include the north end near Sedge's Creek, a beach south of Bridge Bay, and a site on the western shore north of West Thumb. Maps and online aerial imagery show many more elegant barriers around the lake, each probably jealously guarded by its own grizzly bear.