UWM researchers uncover secrets below the surface of the calm waters of Yellowstone Lake.
Kelly Kizer Whitt
Photos from the UWM WATER Institute, unless noted. Click on photos for larger images.
n the northwest corner of Wyoming, high in the Rocky Mountains, lies the majestic Yellowstone National Park. Visitors from around the globe flock here by the thousands every summer to gape in wonder at the steaming geysers, boiling hot springs, bubbling mud pots, and accompanying wildlife. Out on peaceful Yellowstone Lake a handful of UWM researchers are exploring these same types of featuresbut under the water. This aqueous world of geothermal formations and its resident creatures may even provide insight into the beginnings of life on Earth and other planets.
Americas first national park and the lake that bears its name rest partly upon the caldera of the largest volcanic eruption known. About 1.2 million years ago and again 650,000 years ago a giant volcano exploded, forming a crater from the collapsed magma chamber. The northern half of Yellowstone Lake sits within the boundary of this volcanic depression, and its cold, quiet waters belie the seething activity of what lies beneath.
Aguilars forages into the wilds of Yellowstone are a long way from her home country of Mexico, but the setting is not far from her heart. I had a great biology teacher in high school who allowed me to ask questions and search for answers in different topics; she even took me one day to her classes at the university and I loved it, she says. I was always interested in water and organisms that live in different lakes and the ocean. Aguilar has been to Yellowstone Lake for experiments about 10 times now, and three to four undergraduate summer students usually assist the lead investigators on the excursions. Being a role model is important to Aguilar, who says that it is uncommon to see many women in these fields of science, and women of Hispanic backgrounds are particularly scarce.
UWM researchers and student interns began their annual summer pilgrimages to Yellowstone Lake in 1983 and quickly uncovered evidence that the lake floor is not that much different from the topography of the parks dry land. Underwater fissures, or faults, are a result of much of the geologic activity. Craters were found clustered along these faults, with some of the depressions as large as a football field. Scientists believe that hydrothermal explosions are responsible for these circular, steep-walled formations.
Some of the underwater features show evidence of volatility. The resurgent domes on the outlet of the lake at LeHardy Rapids have probably shown the greatest change over a large area, says Aguilars colleague Val Klump, a UWM senior scientist and one of the original researchers at Yellowstone Lake. The individual springs, gas fumaroles, et cetera, within the lake may wax and wane. Klump has even seen changes on the lake floor from one visit to the next. There was a period of a couple years following some rather large seismic activity in the lake basin in which we could not find a deep, yet very small canyon near Stevenson Island. Did it temporarily fill in via slumping? he wonders. We do not really know, but it certainly seemed to disappear.
Another curious feature the researchers have revealed are clusters of spirestall columns of extinct hydrothermal vent conduits consisting primarily of silica, protruding from the floor. In 1997, the UWM team explored a whole crop of the trunk-like features in the Bridge Bay area of the lake, some of them standing in only 45 feet of water. In 1996, these structures were found through acoustic surveys made by National Park Service archaeologists. Many of them are arrayed in long rows, such as the Avenue of Spires, and can reach about 10 feet in height.
The discovery of these amazing underwater features has been due in large part to the use of a Remotely Operated Vehicle, or ROV, which allows scientists to delve into previously inaccessible locations. At more than 7,000 feet above sea level, Yellowstone Lake is the largest high-altitude lake in North America, and is extremely hazardous to work on because of the extreme cold water and the very sudden, violent storms and winds that can come over the mountains, Klump says. Some of the on-site research was originally done through scuba diving, which has its own dangers. The pressure change from going underwater to a high altitude puts a diver at increased risk of decompression sickness. Even though the average lake temperature is perilously cold, some of the underwater vents are much hotter than those on the land, so divers must also be careful to avoid associated hot-water blasts. A few of the more shallow vents are still visited by scientists in scuba gear, but the ROV has been essential in exploring deeper regions.
Through X-ray and electron microscopic observation and analysis, UWM researchers have found the spires to consist mainly of amorphous silica, with diatoms present on the outside of the structures. The diatoms are tiny planktonic organisms with exoskeletons of silica. The hydrothermal waters in the park are often near saturation in dissolved silica, says Klump, and therefore are excellent breeding grounds for the formation of the spires. A dried spire sample appears similar to a sponge made of sandstone. The outer surface is dark brown with bacteria, algae, sponges, and other life forms growing on it, but its interior is white. The spire sample consists of a network of interconnecting tunnels for funneling vent water. All the spires collected so far seem to have been formed up to 12,000 years ago and are no longer considered active.
The minerals drive everything, says Senior Scientist Russell Cuhel as he loads another sample into an analyzer at the WATER Institute facility in Milwaukee. The sulfur and iron that both feed the bacteria and form part of the physical structure of developing spires are particularly elusive. We have to take a significant component of our laboratory to Yellowstone, and that allows us to sample, measure, and analyze our samples hours after they were collected.
The ROV has captured freshwater creatures swirling around the vents like little whirlpools. The bacteria embedded in the formations attract hungry water fleas and snails, which in turn bring the next step up on the food chain: leeches. One vent, dubbed the Trout Jacuzzi, has brought in native cutthroat trout, which normally prefer cooler waters near the surface of the lake. The vents seem to release an unusually high amount of arsenic and mercury into the water, which has been shown in large concentrations in the trout and even in the bears and other animals that eat the trout.
The interaction of biology with geothermal and geochemical energy may be more ancient than any other ecology, Aguilar says, and it therefore provides insight into the evolution of life on Earth and possibly other planets. Bacteria and other life that thrives at high temperatures can be a link to ancient organisms and can be a key to the earthly evolution and development of life, Aguilar explains. One of the theories is that life arose under reducing conditions with high temperatures, similar to the hydrothermal vent systems that are currently found on Earth. These high-temperature systems are relevant to understanding extreme environments on Earth, as well as other planets and moons in our solar system.
The young Earths hydrothermal systems would have started to be present after the surface of the planet had cooled enough to sustain liquid water, Aguilar says. Evidence of hydrothermal systems also existed early in the history of Mars. Continued explorations at Yellowstone have Aguilar and her colleagues excited about how their research contributes to a broader understanding of life in the universe.
The UWM researchers are just beginning to find the pieces of the puzzle that make up Yellowstone Lakes shadowy floor. With each return trip they are able to better complete the picture of its fascinating geologic features, the life that finds a home there, and how it relates to the evolution of life in our solar system.
Many of the images in this article appear in Yellowstone Lake: Join the Expedition!, a 56-page book documenting in text and pictures the exploration of Yellowstone Lake by UWM researchers since 1983. For information about the book or to order, contact Elizabeth Trendel at the WATER Institute (email@example.com or (414) 382-1700) or visit www.amazon.com.