Location:
Mount
Mazama
High Cascades Range
Oregon, U.S.A.
Volcanic Form: Composite volcano; consists of overlapping shield and stratovolcanoes
Formation:
The
Crater Lake Caldera was formed 6850 years B.P. when Mount Mazama exploded
in the largest known eruption from a Cascade Range volcano. Approximately
50 cubic kilometers of magma were ejected during the eruption, causing
the collapse of a caldera ~5km in diameter. Subsequent landslides
widened Crater Lake Caldera to its present size of 8km x 10km.
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LAKES INDEX
REFERENCES
Crater Lake - A Limnological
Wonder
***Add location map***
At a depth of 589 meters, Crater Lake is the 2nd deepest lake in North America, and the 7th deepest lake in the world. Approximately 1.73 x 1010 m3of water resides in the caldera, a volume that would take over 300 years to accumulate under present conditions. At present, inflowing water from precipitation, cold springs, intermittent meltwater streams, and hydrothermal springs is balanced by water loss through evaporation, as well as significant seepage of water through fractures in the lake floor (7.9 x 106 m3/yr) (Williams et. al, 1983).
Several physical and chemical properties
contribute to the wonder and beauty of Crater Lake. Its brilliant
blue color derives from the extremely high clarity of the water.
Low concentrations of total dissolved solids (TDS < 100ppm) and total
suspended solids (TSS< 1ppm) allow light to penetrate deep into the
water column. Photosynthetic organisms take advantage of the available
habitat - carpets of moss grow on the lake bottom at depths up to 130m
(Nelson et.al, 1996), and algae are most abundant in the water columns
between the depths of 100 - 200 meters (Salinas et.al, 1984)
Temperature Profile of Crater
Lake
Although some studies estimate that only 0.45 - 2.5% of the water in Crater Lake originates from hydrothermal sources, the thermal waters have a considerable effect on the physical properties of Crater Lake. Thermal heating can be seen as a gradual increase in water temperature from depths of about 300m to the lake bottom (Figure 1). Heat flow into the deep waters of the lake also causes massive convection, and the lake mixes vertically on a timescale of weeks to months.
Figure 1. Vertical water temperature profile from the
east basin near Merriam Cone. The line lableled
'Max Density' is the curve of the maximum density
from Eklund, 1963.
(Source: Williams and Von Herzen, 1983)
1. Title: The volcanic, sedimentologic, and paleolimnologic history
of the Crater Lake caldera floor, Oregon: Evidence for small caldera evolution.
Authors: Nelson, C.H.; Bacon, C.R.; Robinson, S.W.; Adam, D.P.;
Bradbury, J.P.; Barber, J.H., Jr; Schwartz, D; Vagenas, G.
Source: Geological Society of America Bulletin, vol. 106, p.
684 - 704
Year: May 1994
2. Title: Evolution of the caldera-forming eruption at Crater
Lake, Oregon, indicated by component analysis of lithic fragments.
Authors: Suzuki, K.K.; Kamata, H.' Bacon, C.R.
Source: Journal of Geophysical Research, B, Solid Earth and
Planets, vol. 98, no. 8, p. 14,059 - 14,074.
Year: 1993
3. Title: Mount Mazama and Crater Lake Caldera
Authors: Bacon, C.R.
Source: Proceedings of the Workshop on Geothermal Resources
of the Cascade Range, U.S.G.S. Open File Report p. 37 - 39
Editors: Guffanti, M.; Muffler, L.J.P.
Year: 1985
4. Title: The geology and geochemistry of thirteen cinder cones
at Crater Lake Nattional Park, Oregon
Authors: Prueher, E.M.
Source: Master's Thesis, University of Oregon, 158 pages
Year: 1985
5. Title: Evidence for thermal water in Crater Lake, Oregon
Authors: White, L.D.; Thompson, J.M.; Maley, C.A.
Source: Eos, Transactions, American Geophysical Union, vol.
66, no 46, p. 1146
Year: November 12, 1985
6. Title: On the terrestrial heat flow and physical limnology
of Crater Lake, Oregon.
Authors: Williams, D.L.; Von Herzen, R.P.
Source: Journal of Geophysical Research, B., vol. 88, no. 2,
p. 1094 - 1104
Year: 1983
7. Title: Does Crater Lake, Oregon, have a discernible outlet?
Authors: Thompson, J.M.; White, L.D.
Source: Eos, Transactions, American Geophysical Union, vol.
64, no. 45, p. 895.
Year: 1983
8. Title: Crater Lake, gem of the Cascades; the geological story
of Crater Lake National Park
Authors: Cranson, K.R.
Publisher: K.R. Cranson Press, Lansing, MI, U.S.A.
Year: 1980
9. Title: Stability of lakes near the temperature of maximum
density
Authors: Eklund, H.
Source: Science, vol. 142, p. 1457 - 1458
Year: 1963