Photographer: Marli Miller; Marli's Website
Summary Author: Marli Miller

The hot springs shown above, linked by a shallow overflow channel, reside in the West Thumb Geyser Basin of Yellowstone National Park. Sinter, which is hydrothermally precipitated silica, forms the white crust while heat-tolerant bacteria and algae form the yellows and browns.

Although it's one of the smallest of Yellowstone’s geyser basins, West Thumb is significant because it occupies part of a caldera within the much-larger and somewhat older Yellowstone caldera. West Thumb caldera was formed by an eruption between 150,000 and 200,000 years ago, whereas the main Yellowstone eruption occurred about 600,000 years ago. On a map, the West Thumb caldera appears as the distinct elliptical area that makes up the western part of Yellowstone Lake. With an area of about 30 sq. mi (78 sq. km), it compares in size to Crater Lake, Oregon. By contrast, the Yellowstone caldera exceeds 1,000 sq. mi. (2,590 sq. km) in area. Photo taken in July 2008.

Photo details: Camera Maker: Canon; Camera Model: Canon EOS 5D; Lens: EF24-105mm f/4L IS USM; Image Focal Length: 32.0mm; Aperture: f/9.0; Exposure Time: 0.025 s (1/40); ISO equiv: 100; Exposure Bias: -0.33 EV; Metering Mode: Spot; Exposure: program (Auto); White Balance: Auto; Flash Fired: No (enforced);
Orientation: Normal; Color Space: Adobe RGB (1998).

• West Thumb Hot Springs, Wyoming Coordinates: 44.4154952, -110.5754846
• Related Links
  • Mammoth Hot Springs
  • Geologic Map of Yellowstone
  • The World's Most Memorable Hot Springs
  • Algae Database
• Earth Observatory
  • Grand Prismatic Spring, Yellowstone

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