Crater Lake has no streams flowing into or out of it. as a result, the water is extraordinarily clear, and the lake has a striking blue hue.

Table of contents

1 Geology 2 History 3 Activities 4 References 5 External links

Geology

Volcanic activity in the area is fed by subduction off the coast of Oregon as the Juan de Fuca Plate slips below the North American Plate (see plate tectonics). Heat and compression generated by this movement has created a mountain chain topped by a series of volcanoes, which together are called the Cascade Range. The large volcanoes on the range are called the High Cascades. However, there are many other volcanoes in the range as well (most are much smaller).

Mount Mazama began life in much the same way as other High Cascades and around the same time (400,000 years ago as overlapping shield volcanoes). Over time alternating layers of lava flows and pyroclastic flows built Mazama's overlapping cones until it reached about 11000 feet (~3550 meters) in height.

As the young stratovolcano grew, many smaller volcanoes and volcanic vents were built in the area of the park and just outside what are now the park's borders. Chief among these were cinder cones. Although the early examples are gone (cinder cones erode away easily), there are at least 13 much younger cinder cones in the park that still retain their distinctive cinder cone appearance (11 more are outside park borders). There continues to be debate as to whether these minor volcanoes and vents were parasitic to Mazama's magma chamber and system or if they were related to background Oregon Cascade volcanism.

After a period of dormancy, Mazama became active again. Then around 4860 BC, Mazama collapsed into itself in a tremendous volcanic eruption, loosing 2500 to 3500 feet (760 to 1070 meters) in height, The eruption formed a large caldera that was later filled with a deep blue lake known today as Crater Lake.

The eruptive period that decapitated Mazama also laid waste to much of the greater Crater Lake area and deposited ash as far east as the northwest corner of what is now Yellowstone National Park as far south as central Nevada, and as far north as southern British Columbia.

Some notable park features that were created by this huge eruption are;

• The Pumice Desert - a very thick layer of pumice and ash leading away from Mazama in a northerly direction. Even after thousands of years, this area is largely devoid of plants due to excessive porosity (meaning water drains through quickly) and poor soil (regolith would be a more descriptive term).
• The Pinnacles - When the very hot ash and pumice came to rest near the volcano, it formed 200 to 300 foot (60 to 90 meter) thick gas-charged deposits. For perhaps years afterward, hot gas moved to the surface and slowly cemented ash and pumice together in channels and escaped through fumeroles. Erosion later removed most of the surrounding loose ash and pumice, leaving tall pinnacles and spires.

• Mount Scott is a steep andesitic cone whose lava came from magma from Mazama's magma chamber (geologists call such volcano a 'parasitic' or 'satellite' cone). Volcanic eruptions apparently ceased on Scott sometime before the end of the Pleistocene (a large cirque on Scott's northwest side was not modified by post-ice age volcanism).
• In the southwest corner of the park stands Union Peak, an extinct volcano whose primary remains consist of a large volcanic plug (this was lava that solidified in the volcano's neck).
• Crater Peak is a shield volcano primarily made of andesite and basalt lava flows but topped by andesitic and dacite tephra.
• Timber Crater is a shield volcano located in the northeast corner of the park. Like Crater Peak, it is made of basaltic and andesitic lava flows, but unlike Crater it is topped by two cinder cones.

Judge William Gladstone Steel led late 19th century efforts to have the greater Crater Lake area designated a national park. With the help of geologist Clarence Dutton, Steel organized a USGS expedition to study the lake in 1886. The team used pipe and piano wire to obtain depth soundings in different parts of the lake (their deepest sounding was very close to the modern official depth). At the same time a topographer surveyed the area and created the first professional map of the Crater Lake area (Steel helped name many features).

Partly based on data from the expedition and lobbying from Steel and others, Crater Lake National Park was established May 22nd, 1902.

Highways were later built to the park to help facilitate visitation. The most popular road in the park is Rim Drive, which, as the name suggests, follows a scenic route around the caldera rim.

Activities

Observation points along the caldera rim are easily accessible by automobile via Rim Drive. The best vantage point, however, is from Mt. Scott (8926 feet, 2720.6 meters). Getting there requires a fairly steep 2.5 mile (4 km) hike from the Rim Drive trailhead. On a clear day from Mt. Scott's summit, a hiker can see for 100 miles (160 km) and can, in one single view, take in the entire caldera. Also visible from this point are the white-peaked High Cascade volcanoes to the north, the Columbia River Plateau to the east, and the Western Cascades to the west (with the more distant Klamath Mountains still further west).

References