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 Crater
Lake is located in southern Oregon on the crest of the Cascade
Range, 100 miles (160 km) east of the Pacific Ocean. It lies
inside a caldera, or volcanic basin, created when the 12,000
foot (3,660 meter) high Mount Mazama collapsed 7,700 years ago
after a large eruption. The lake is approximately 5 miles (8 km)
wide, and is surrounded by steep rock walls that rise up to 2,000
feet (600 meters) above the lake's surface.
Following the collapse of Mount Mazama, lava poured into the
caldera at several places even as the lake began to rise. These
flows created underwater features as well as Wizard Island, a
cinder cone that rises 764 feet (233 meters) above the lake and
is surrounded by black volcanic lava blocks.
Temperatures within the top 260 feet (80 meters) of the lake
vary between 32°F (0°C) in the winter and 66°F in
the summer. Water beneath the top layer remains near 38°F
(2°C) all year long. The lake rarely freezes in winter because
of its large heat content, windy surface conditions, and relatively
mild air temperatures.
Generous amounts of winter snow, averaging 533 inches (1,354
cm) per year, supply the lake with water. There are no surface
inlets or outlets to the lake. Evaporation and underground seepage
balance the inputs of rain and snow and prevent the lake from
becoming any deeper. At 1,943 feet (592 meters), Crater Lake
is the deepest lake in the United States, the seventh deepest
in the world!
Scientists continue to conduct research in Crater Lake. Every
summer, scientists measure the water's chemistry and clarity
and survey the numbers of plants and animals in the water, looking
for patterns, trends, and relationships. In 1988 and 1989, scientists
explored the bottom of the lake with a one-person submarine.
Among other discoveries, they found hot springs at several locations.
The springs were surrounded by mats of bacteria thriving in the
warm, mineral-rich water.
Why
is Crater Lake so Blue?
 The dramatic
color of Crater Lake is the product of its great depth, the purity
and clarity of its water, and the way light interacts with water.
Water molecules absorb the longer wavelengths of light better
(reds, oranges, yellows, and greens). Shorter wavelengths (blues)
are more easily scattered than absorbed. In the deep lake, some
of the scattered blue light is redirected back up to the surface
where we can see it. Around the edges where the water is less
deep, some of the unabsorbed green light is reflected back up,
too. Although the color of the lake can vary from day to day
depending on wind, cloud cover, and the angle of the sun, the
different shades of blue are always spectacular.
 Since
the lake is filled almost entirely by snowfall, it is incredibly
pure. Sunlight is able to penetrate the waters of Crater Lake
to great depths. Researchers using an instrument called a "Secchi
disk" can easily determine lake clarity. They simply lower
the 8-inch black and white disk into the water, and measure the
depth at which the disk is no longer visible from the surface.
For most lakes, readings deeper than 100 feet (30 meters) are
rare, but on June 25, 1997, scientists recorded a world record
clarity reading of 142 feet (43.3 meters)!
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Inside
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Facts & Figures
Volume of water in the lake: 5 trillion gallons (19 trillion liters)
Lake surface area:
20.6 sq. mi. (5,385 ha)
Greatest depth:
1,943 ft. (592 m)
Average depth:
1,148 ft. (350 m)
Widest point:
6.02 mi. (9.69 km)
Narrowest point:
4.54 mi. (7.31 km)
Highest point on the rim: 1,980 ft. (604 m) above the lake
Average height of the rim: 1,000 ft. (300 m) above the lake
Height of Wizard Island: 764 ft. (233 m) above the lake
Size of the park:
286 sq. mi. (78,117 ha)
Highest point in the park: 8,929 ft. (2,721 m) at Mt. Scott
Visitors per year:
about 500,000
Annual precipitation:
69 in. (175 cm)
Average annual snowfall: 533 in. (1,354 cm)
Record annual snowfall: 879 in. (2,233 cm), 1932-33
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