Paoha Island is a volcanic island in Mono Lake, an endorheic lake in the U.S. state of California. Formed by a series of eruptions in the 17th century, Paoha is composed of lakebed sediments deposited above volcanic domes. It is one of two major islands in the lake, the other being the smaller Negit Island. Its name comes from a Native American word, Pa-o-ha, describing the abundant hot springs and fumaroles on its surface.
As described in Wikipedia, only about 350 years ago, before the mid-17th century, the present-day Paoha Island did not exist. Volcanic eruptions on the lakebed gave rise to the island, which eventually rose to 6,670 feet (2,030 m) above sea level, 290 feet (88 m) above the present-day elevation of Mono Lake. The pale color of the island is attributed to lakebed sediments rising above the lake surface along with the volcanic material.
The volcanic origin of the island gave rise to many vents, hot springs, fumaroles and mudpots on the surface of the island. An eruption sometime before the twentieth century created a crater lake that is said to be shaped like a heart. Paoha Island is the younger of the two Mono Lake islands; Negit rose about 1,350 years before Paoha. Paoha Island was named by Israel Cook Russell, a well-known American geologist, in the late 19th century. It supposedly received its name from the Paiute word, pa-o-ha, for spirits they believed to exist in Paoha Island's hot springs. In naming the islands, Russell (1888) "preferred to record some of the poetic words from the language of the original inhabitants of the valley … There is a story about diminutive spirits, having long, wavy hair, that are sometimes seen in the vapor wreaths ascending from hot springs. The word pa-o-ha, by which these spirits are known, is also used at times to designate hot springs in general. We may therefore name the larger island Paoha Island, in remembrance, perhaps, of the children of the mist that held their revels there on moonlit nights in times long past."
The surface sediments of Paoha Island consist primarily of clay and marl, which are responsible for the pale surface. Volcanic ash is scattered all around the island and basalt is exposed at some of the lower elevations. There are also river-deposited sediments and granite rocks.
The Mono Lake volcanic field, east of Yosemite National Park and north of the Mono Craters, consists of vents within Mono Lake and on its north shore. The most topographically prominent feature, Black Point, is an initially sublacustral (below lake level) basaltic cone that rises above the northwest shore and was formed about 13,300 years ago when Mono Lake was higher. Lava domes and flows form Negit and parts of Paoha islands within Mono Lake. More information can be found through the USGS Volcano Hazards program describing the Mono Lake Volcanic Field. An article from NASA describes, the shoreline of Pahoa Island in hypersaline Mono Lake in California is characterized by numerous volcanogenic hot springs that display a wide range of temperatures between 30 and 85 degrees C. A variety of distinctive photosynthetic microbial mats are evident in these hot springs and their spatial distribution appears to be a function of water temperature. The suboxic hydrothermal waters of these seeps typically contain ~100 uM dissolved arsenic, which is rapidly oxidized from arsenite [As(III)] to arsenate [As(V)] as the springs flow over these microbial communities. NASA conducted experiments with anaerobic cultures of red or green photosynthetic bacteria from these hot springs, which NASA amended with radio-labeled 73As(III) or 73As(V) and incubated at 42 degrees C to measure arsenite oxidation and arsenate reduction activity. In order to assess the potential for As(III) to serve as an electron donor during anoxygenic photosynthesis, As(III) oxidation incubations were conducted under both light and dark conditions. Both light and dark incubations of these thermophiles rapidly oxidized amendments of 100 uM As(III) within 7 hours of incubation, however no significant difference was observed in the rate of As(III) oxidation for light compared to dark samples. Arsenate reduction was also observed in both light and dark anaerobic cultures after 48 hours incubation. In all cases, As oxidation or reduction activity was eliminated by autoclaving. These results suggest that biological As(III) oxidation by these bacteria is primarily a mechanism of detoxification or chemoautotrophy, however the potential significance of As(III) as a photosynthetic electron acceptor will be discussed.
To claim this cache as a find:
- Describe the geologic feature at the posted coordinates.
- Climb to the top of the western ridge and describe the land surface on the western shore of the island.
- Which island is older, Negit or Paoha?
- Describe your experience.
- Send your responses to me prior to logging this EarthCache as a find.
Thank you, enjoy and be safe.
Congratulations to Plazmo and Pirates2+2 for being FTF, sharing their pictures, and describing their findings!