Llao's bath, Crater Lake's hydrothermal vent.

Crater Lake

Discoveries at the bottom of Crater Lake are fascinating to scientists. Hydrothermal, biological, and geological studies of the lake bottom were conducted with the Deep Rover Submersible. Deep Rover is a highly technical submarine that the National Park Service, National Geographic Society, and U.S. Geological Survey leased from Can-Dive, Inc., a company based in Vancouver, British Columbia. Deep Rover provides a rare opportunity for scientists to study and explore the hidden secrets of Crater Lake.

Hydrothermal studies include the discovery of blue hydrothermal pools, stream-like channels, and spires on the lake floor. Hydrothermal pools are highly saline; salt content in these pools is as much as 10 times higher than the surrounding lake water. The presence of the salts makes the liquid in the pool heavier than lake water. The pools appear blue because of the optical properties of the chemically enriched fluids. Llao's Bath is a discrete blue-colored pool of saline water found on the lake floor. Small stream-like features found along the base of the northeast caldera wall were 5-8 cm (2-3 in) wide and deep, and exhibited erosional flow patterns. The channels were lined with brilliant gold bacteria and often terminated down slope in a series of blue pools. Spire remnants found along the east caldera wall provide a record of past hydrothermal activity. The spires form when chemically rich hydrothermal fluids come in contact with cold ambient water and the chemicals precipitate out of solution to form chimneys around the vents. The spires had a chemistry indicative of a hydrothermal origin and a morphology consistent with underwater formation.

Biological studies include the discovery of bacteria colonies associated with hydrothermal fluids. These yellow-orange mats consist of thousands of Gallionella and Leptothrix bacteria. Golden-colored bacteria were found surrounding Llao's Bath. A thick band of moss, Drepanocladus aduncus, encircles the lake at depths from 26-140 m (85-460 ft). It hangs like icicles on vertical cliffs and forms thick, lush fields on the gentler slopes around Wizard Island. A fascinating discovery is the animals living in the deepest basin of Crater Lake (589 m, or 1,932 ft). These animals which withstand such high water pressure include flatworms, nematodes, earthworms, copepods, ostracods, and the midge fly Heterotrissocladius.

Geologic studies have expanded our knowledge of the eruptive history of Mount Mazama and the bathymetry of Crater Lake. Rock samples from the caldera walls are from lava flows of Mount Mazama, but rock samples from the lake floor predate Mount Mazama. Scientists were able to further analyze the postcaldera volcanism to determine whether it erupted beneath lake water or before the lake was filled. Lava flows that formed the central platform (located east of Wizard Island) are aerial formations; that is, they were deposited before the lake was filled. Merriam Cone and most of the submerged portion of Wizard Island are subaerial formations; that is, they formed beneath the water surface.

Crater Lake color bar.

For more information on Crater Lake ecology, please see: footer image. Why enter a sleeping volcano in a submarine? Image of Llao's Bath was acquired from this site.