Lake Mead near Hoover Dam

Vertical

View of Lake Mead in the vicinity of Hoover Dam (mostly hidden, far left): A fall in water level is revealed by the white “bathtub ring,” where the surface layers of previously inundated sandstone have been altered by the action of cyanobacteria, or blue-green algae.

NPS Photo by Susann a Pershern, Submerged Resources Center

Horizontal

View of Lake Mead in the vicinity of Hoover Dam (mostly hidden, far left): A fall in water level is revealed by the white “bathtub ring,” where the surface layers of previously inundated sandstone have been altered by the action of cyanobacteria, or blue-green algae.

NPS Photo by Susann a Pershern, Submerged Resources Center

Thumb

View of Lake Mead in the vicinity of Hoover Dam (mostly hidden, far left): A fall in water level is revealed by the white “bathtub ring,” where the surface layers of previously inundated sandstone have been altered by the action of cyanobacteria, or blue-green algae.

NPS Photo by Susann a Pershern, Submerged Resources Center