Yellowstone Lake

Yellowstone Lake is the largest body of water in Yellowstone National Park. The forest and valleys surrounding Yellowstone Lake had been populated with Native Americans since pre-historic times. The first human of European descent to see the lake was trapper John Colter in the early 19th century. During the fur trading era of 1820 - 1840, the lake was probably visited by many trapping parties moving through the park region. In the southwest area of the lake the West Thumb geothermal area is easily accessible to visitors. Geysers, fumaroles and hot springs are found alongside and even in the lake.  In recent years (as of 2004), the ground under the lake has started to rise significantly, indicating increased geological activity, and limited areas of the national park have been closed to the public. As of 2005, no areas are currently off limits aside from those normally allowing limited access such as around the West Thumb Geyser Basin. There is a 'bulge' about 2,000 feet long and 100 feet  high under a section of Yellowstone Lake, where there are a variety of faults, hot springs and small craters. Seismic imaging has recently shown that sediment layers are tilted, but how old this feature is has not yet been established.