Friday, January 9, 2009

Day 203: Tracing the Pleistocene

map of Pleistocene Lakes

Early this coming summer I am going to be doing some research in the American west. I have a long list of places to see, but two sites of great interest are the remnants of Lake Lahontan and Lake Bonneville, dating to the Pleistocene. The Pleistocene dates between 10,000 and 1.8 million years ago, but Lake Lahontan formed about 20,000 years ago and Bonneville up to 32,000 years ago. These lakes now have all but now disappeared, but the amazing part is that bits of them remain in the form of smaller lakes and expansive playas where the lake beds use to be. The Great Salt Lake in Utah is a fraction of the size of Lake Bonneville, but was once a part of this lake which covered almost 20,000 square miles and was up to 1,000 feet deep. From the flat white surface of the Bonneville Salt Flats (see our limit case postcards for an image) you can actually see old shorelines on the mountains surrounding the flats.

Lake Lahontan covered 8,000 square miles and was up to 800 feet deep. Today, Pyramid Lake (see Day 107 when I visited this lake last October ) Walker Lake, and occasionally Lake Winnemucca are the only remnants. The immensely flat, dry and harsh environment of the Black Rock Desert (site for Burning Man) happens upon the playa that once was Lake Lahontan. It is one of the flattest places on earth.

I dig these lakes, as they are an incredible reminder that things are and always have been on the move. I love the idea of having a chance to be where they once were.

This timeline of deep time from PBS is an excellent visual way to start to get your head around these spans of time involved, and just how ephemeral we are.

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