Crater Lake Historic Resource Study

V. Geological and Biological Information on Crater Lake Area (continued)

C. Description of Lake

1. Statistics

Crater Lake is nestled in a collapse caldera, a large, basin-shaped volcanic depression produced by the failure of the roof of a magma chamber due to removal of the magma by voluminous pyroclastic or lava eruptions or by the subterranean withdrawal of magma. [8] The lake occupies only about one-eighth of the entire park area, lying in its center at an elevation of about 6,177 feet. Roughly circular in shape, about six miles across at its widest point, and covering twenty square miles, it is rimmed by nearly twenty-six miles of colorful lava cliffs rising from 500 to 2,000 feet above the lake's surface.

Crater Lake is the deepest lake in the United States, the second deepest in the Western Hemisphere, and the seventh deepest in the world, dropping downward to 1,932 feet just southeast of Merriam Cone. It is eclipsed by five other lakes in the world that exceed 2,000 feet and by Lake Baikal in Soviet Central Asia, the world's deepest at 5,315 feet. Although not fed by major springs or drained by rivers, the Crater Lake caldera holds a relatively unchanging volume of water- -more than four cubic miles--an amount that usually varies only within five feet of the 6,170-foot mark. This constancy has resulted from a balance between precipitation on the lake's surface and moisture lost through evaporation and seepage (percolation) through rock strata. Due to its high elevation on the crest of the Cascade Range, Crater Lake receives on the average fifty feet of snow a year, and once more than seventy, with snowfalls covering the park for nearly eight months of the year. Snow melt also contributes to the water level. The water in Crater Lake is always cool, varying from about 64°F. at the surface to a constant 38°F. at depths of 300 feet and beyond. The lake was solidly frozen over in 1949, carrying two to twelve inches of ice. [9]

2. Color

The lake? The Sea of Silence? Ah, yes, I had forgotten. . . . But fancy a sea of sapphire set around by a compact circle of the great grizzly rock of Yosemite. . . . The one thing that first strikes you after the color, the blue, blue, even to blackness, with its belt of green clinging to the bastions of the wall, is the silence. . . . [10]

Although there are larger and deeper lakes in the world, and also other crater lakes--in Asia, South America, Europe, Japan, Australia, Mexico, and Hawaii--Crater Lake is unique for several reasons. First, because the rim walls of volcanic rock rise to such imposing heights and are often reflected in the water to such a degree that reality and the image are one; second, because of the presence of a crater within a "crater"; but primarily because of the puzzling brilliance and depth of its color, a source of extreme wonderment when viewed on a clear day in contrast to the encircling rocky rim of the old volcano with its yellow and rust-colored hues.

Part of the mystery surrounding the color of the water was due to the fact that although from the rim edge the lake surface appears to be of the deepest shade of blue, a glassful taken from the surface shows that the water is actually colorless and remarkably free of sediment, a result of its being fed by direct precipitation rather than by stream flow or seepage. Near the shore it is possible to see the bottom through fifty to seventy-five feet of water, and aquatic moss, which requires sunlight and which can live no deeper than 120 feet in most lakes, has been found growing 425 feet below the surface in Crater Lake.

Studies of the lake water were undertaken, leading scientists to the conclusion that the blueness of Crater Lake is due in great part to the fact that its deep waters remain in a nearly static condition, free of suspended sediment or dissolved matter. The blue and green wave lengths in the sunlight hitting the lake are bounced between and off the water molecules and reflected back upward to the viewer, while the rays of other colors are absorbed. This is a condition especially noticeable in quiet waters of great depth, at a slight distance from the shore, and relatively free of suspended matter. More scientifically, the process is described in this way:

. . the predominant color of the lake is due to multiple scattering of light by the water molecules. Superimposed upon this is the reflection of sky, clouds and crater walls. On a clear day, with rippled surface, the reflection phenomena are entirely submerged by the scattered light. If the sky is overcast, the only light the lake receives is from the clouds; hence the color is predominately gray. With a glassy surface on a clear day, the reflection phenomena may predominate, depending on the position of the observer. The deepening of the color as one approaches the lake is probably due to the fact that at a distance the weaker multiple scattered light, which is the bluest in color, is lost by atmospheric interference and by addition of extraneous light, while at the water surface it has its full effect. . . .

In a word, the blue of Crater Lake and the blue of the sky are due to the selective scattering of rays of light which have been diverted from a straight course by molecules of water, in the one case, and, in the other, by molecules of air . . . . [11]

Blue is made up of the shortest light waves . . . and it is these that are sent back to the observer due to the extreme depth and purity of the lake water. [12]

D. Volcanic Parks

1. Importance in National Park System

Mounts Garibaldi, Baker, Glacier Peak, Rainier, St. Helens, Adams, Hood, Jefferson, Three Sisters, Mazama, Shasta, and Lassen Peak all are part of a long string of volcanoes stretching in a broad arc from South America north and west toward Alaska, Japan, and Indonesia. Referred to with respect as the "Ring of Fire" because of its frequent and dramatic eruptions, this chain includes about seventy-five percent of the world's 1,300 active volcanoes. In the Cascade Range, the high peaks we admire today have all been active for the last million years at least, with Mounts Baker and Rainier in Washington and Hood in Oregon all restless even into the nineteenth century. In the twentieth century, Lassen Peak was the center of attention on this continent from about 1914 to 1921 as it periodically expelled steam, volcanic rock fragments, and lava. Even its violence, however, has been immensely overshadowed by the spectacular self-destructive explosion of Mount St. Helens on May 18, 1980. All this activity tends to suggest that the Cascade Range is not volcanically dead, but only dormant, thereby making it one of the best areas in which to observe volcanic movements today. Four of the National Park Service's volcanic parks--Lassen Volcanic NP, Mount Rainier NP, Crater Lake NP, and Lava Beds NM--are connected with the Cascade chain. Oregon itself has a wider variety of volcanic rock than any other state, and its variety of volcanism and long period of activity is unexcelled even by Hawaii.

2. Importance of Crater Lake National Park

The state of Washington's Mount St. Helens offers a tremendously exciting opportunity for serious scientific study of the immediate effects of a volcanic explosion on the environment. Oregon's Crater Lake, on the other hand, enables visitors to comprehend the regenerative abilities of the earth after volcanic activity. Here one can look without fear but with a sense of awe over a land that bears the scars of an earlier violence already partially healed by forest and meadow. The landscape and scenic details of such a volcanic area are unique among other national park units:

of the several processes of world-making, all of which are progressing to-day at normal speed, none is so thrilling as volcanism, because no other concentrates action into terms of human grasp. Lassen Peak's eruption of a thousand cubic yards of lava in a few hours thrills us more than the Mississippi's erosion of an average foot of her vast valley in a hundred thousand years; yet the latter is enormously the greater. The explosion of Mount Katmai, the rise and fall of Kilauea's boiling lava, the playing of Yellowstone's monster geysers, the spectacle of Mazama's lake-filled crater, the steaming of the Cascade's myriad bubbling springs, all make strong appeal to the imagination. They carry home the realization of mysterious, overwhelming power. [14]

As early as the 1880s J.S. Diller of the Geological Survey said of Crater Lake that it "affords one of the most interesting and instructive fields for the study of volcanic geology to be found anywhere in the world." Ancient Mount Mazama has been important in scientific circles because of the variety of ways in which the ash from her eruption, which can be easily identified by the particular minerals it contains, can be utilized in geological studies: helping to date archeological discoveries in the Northwest; helping to formulate a timetable of glacial movement and melting patterns; helping to determine the length of time it has taken modern soils to develop from various types of deposits; functioning as a time marker in establishing geologic chronology; and helping to determine types of early plant life by its position above or below the pollen immersed in bogs. [16]

Through the years Crater Lake and its surrounding forest lands have been the subject of research in the fields of geology, archeology, paleontology, botany, geography, I imnology, zoology, ecology, biology, and physics by scientists from this country and around the world.