Science / Medicine : Crater Lake Offers Scientists ‘Teacup’ for Studying Deep Secrets of the Sea
Oregon’s deep and incredibly blue Crater Lake is more than 100 miles from the Pacific Ocean. One wouldn’t think of this pristine, wooded mountain resource, set aside as a national park in 1902, as a place that would intrigue a seasoned oceanographer like Jack Dymond of Oregon State University.
Dymond is far more accustomed to exploring the depths of the sea, as he was doing 8,000 feet down near the Galapagos Islands in 1977. But one day last summer, Dymond could hardly restrain a whoop of glee as he viewed videotapes taken at the 1,500-foot floor of this unique freshwater lake.
Scientists classed what the tapes captured as a “geothermal vent,” one of many clues they use to determine how the fires of volcanism continue to shape and reshape the still-cooling Earth.
To the untrained eye, the vent did not look like much: a small fissure on the lake floor, perhaps 2 inches wide, from which lazily oozed a whitish substance that Dymond said looked “like cigarette smoke curling upward.”
But discovery of the vent, which Dymond hopes to reconfirm and further explore when he descends in a Jules Verne-like submersible next summer, was important news to the National Park Service. The Park Service has long wondered whether the caldera that forms Crater Lake is still geothermally active. It was formed 6,800 years ago when Mt. Mazama, a volcanic peak in the Cascades range both feared and revered by prehistoric Indians, erupted with a violence at least 42 times more powerful than that of Mt. St. Helens in Washington in 1980.
For Dymond and his colleagues, there is an interesting fringe benefit to the discovery. In addition to providing valuable information about the origins of the lake and the current geothermal activity beneath it, further study of the vent, remote from the oceans though it may be, could greatly expand knowledge of how the seas--particularly the deep ocean basins like those off the Galapagos--were formed millions or billions of years ago.
“It’s been called ‘oceanography in a teacup,’ ” Dymond said, “meaning that there are many similarities (between) the deep ocean floor and the floor of Crater Lake; we can learn about one by studying the other. The processes that formed Crater Lake really aren’t much different from those that formed the oceans. Only here in Crater Lake they were much more recent, and we can study them in a much more accessible, safer environment. And at far less expense.”
“What we’re looking for in the lake,” Dymond added, “is an entire range of processes--biological, chemical, physical--which happen to be the same processes we are studying, under more difficult circumstances, in the oceans.”
Scientists generally agree on how the oceans got their water; over the billions of years it took the earth to cool after its fiery origins, they say, rain alternately fell into the basins and then evaporated from the heat, fell again and remained when the Earth became cooler than the boiling point of water.
Since 1977, when Dymond and other oceanographers discovered geothermal vents on the sea floor near the Galapagos, volcanic activity has been increasingly suspected as a major source of the ocean’s chemistry, for shifting changes on the sea floor, even for biological production--or the lack of it--in the deep sea.
So it is with Crater Lake. “The lake is a lot like an ocean basin, only in miniature,” he said. “The oceans have the same terrific blue water, just like Crater Lake. The clarity is much the same. And geothermal activity may also explain why Crater Lake, unlike most lakes but very much like the deep ocean, is biologically at a very low level.”
The analogy wouldn’t apply to many lakes. Only one other deep water lake in the world--Africa’s 4,823-foot-deep Lake Tanganyika--has the great depth, geothermal input and other features that make the lake-ocean comparison valid, according to scientists.
To Dymond, therefore, finding the Crater Lake vent was a serendipitous discovery with importance beyond the Park Service’s desire to merely learn more about a unique resource it is assigned to protect.
Volcanologists classify Crater Lake as a dormant volcano, one which has not been active in historic times. Mazama, they say, probably has not experienced even a minor eruption in 1,000 years. At 1,932 feet, it is the deepest lake in the United States, the sixth deepest and one of the clearest and bluest in the world.
The caldera was formed when the slopes of Mazama collapsed during the eruption nearly seven millennia ago, then fell into a huge subterranean void left by the exploding magma.
With a surface elevation of 6,176 feet, Crater Lake gathers very little runoff from the surrounding terrain. Its water level remains fairly constant because evaporation almost exactly equals what it gets from precipitation. And, unlike many lakes but very much like the ocean, its crater is virtually a closed basin. The only major difference from an ocean basin, according to Dymond, is that while some Crater Lake water may be draining out the bottom, ocean basin water does not.
“But in most respects, the processes of ocean and lake are very similar, and studying them is very exciting,” he said.
Dymond, along with an Oregon State University colleague, Robert Collier, began to suspect the presence of hydrothermal activity in Crater Lake in 1983 when they launched the intensive study of the lake’s geochemistry and limnology, funded by the Park Service.
“Our samples,” Dymond said, “revealed the presence of helium isotopes in high concentrations, and minerals such as chloride(s) and magnesium--all indicating thermal activity, just as we found in the Galapagos.” Also, water sampled on the lake bottom was slightly warmer than that at a level just above the bottom, indicating a possible “hot spot.”
Last summer’s vent discovery utilized an unmanned, sled-like submersible called Phantom, equipped with a video camera and operated from a surface vessel. In addition to the vent itself, the camera recorded several orange-colored spots near the fissure that, Dymond feels, may be evidence of iron, one of the sediments carried by hydrothermal fluids.
Next summer, in a continuation of the study, Dymond and Collier plan to use a larger, more sophisticated, manned submersible called Deep Flight. The vehicle has “arms” that can be controlled by its pilot to pick up objects at working depths of at least 3,000 feet.
The pilot can either maneuver the vehicle himself, or it can be moved about with a tether handled by a surface crew.
Although records are somewhat unclear on the subject, the dive could become the deepest manned descent ever made in a freshwater lake.
Although it may applaud the “oceanography in a teacup” experiments, the Park Service also is concerned about the plans of a geothermal steam development company, California Energy Corp. of Santa Rosa, to commercially exploit Mazama’s geothermal energy by drilling wells just outside the park boundary. Officials are worried that drilling into the subterranean “plumbing,” if it connects with that under the lake, could adversely affect Crater Lake’s ecology.
According to Jim Milestone, Crater Lake National Park resource specialist, CalEnergy drilling “could affect water, heat and chemical budgets, internal lake circulation, lake productivity, and clarity.”
CalEnergy began drilling the first of two exploratory holes in September, 1986, in Winema National Forest, adjoining the national park. Representing an investment of about $2 million so far, the work was suspended when research developed the hydrothermal vent possibility. Several environmental groups, including the Sierra Club and Oregon Natural Resources Council, have banded together to block further drilling by CalEnergy.
The summer deep dive could well decide the fate of CalEnergy’s hopes to commercially exploit the still-smoldering fires of ancient Mazama.
It could also add, comfortably and vicariously, to human knowledge of the most mysterious of all Earth’s regions, and the most difficult to explore--the deep oceans.
