Aerial view of Black Opal Pool, Black Diamond Pool, and part of Wall Pool, all in Biscuit Basin, Yellowstone National Park, taken in 1959

Aerial view of Black Opal Pool, Black Diamond Pool, and part of Wall Pool, all in Biscuit Basin, Yellowstone National Park, taken in 1959 sometime after the Hebgen Lake earthquake (which occurred on August 17 of that year). The division between Black Diamond Pool and Wall Pool was less prominent at this time, which might be why park geologist George Marler used a single name to encompass both features. Note the many boulders strewn about in the bottom half of the image. YELL photo #35736, courtesy of the Yellowstone National Park archives.