05 General Nature of the Survey Area

Soil Survey of Crater Lake National Park, Oregon 

General Nature of the Survey Area

This section provides general information about the park. It discusses history and development, geology, and climate.

History and Development

Crater Lake National Park was established in 1902. It was “dedicated and set apart forever as a public park or pleasure ground for the benefit and enjoyment of the people of the United States” (16 USC 121). The act that established the park required that adequate measures be taken for the “preservation of the natural objects…the protection of the timber…the preservation of all kinds of game and fish.” The act required that the park be available, under regulations established by the U.S. Department of the Interior, for use by “scientists, excursionists, and pleasure seekers.”

Subsequent legislation, including the National Park Service Organic Act and the Redwood Act, emphasize the protection, preservation, and interpretation of the natural and historic objects, scenery, and wildlife of all national parks, including Crater Lake National Park. Park resources are to be managed in such a way as to maintain them in an unimpaired condition for the enjoyment of present and future generations.

The legislation enabling Crater Lake National Park also provides for visitor accommodations by stating that “restaurant and hotel keepers, upon application to the Secretary of the Interior, may be permitted by him to establish places of entertainment within the Crater Lake National Park for the accommodation of visitors, at places and under regulations fixed by the Secretary of the Interior, and not otherwise.”

The park is a vital element in a diverse regional recreation complex. Many people visit the park as part of a north-south trip to various parks and scenic areas in Oregon and northern California. Crater Lake has historically been the leading draw for visitors to southern Oregon. More than 500,000 people visit the park annually, most of which visit during the brief summer season. A greater number each year, however, are making use of the winter recreation potential of the park. Long snowy winters and mild short summers dominate the seasonal weather pattern at Crater Lake National Park. The park receives abundant snow in October through May. The average annual snowfall is about 500 inches. Generally, snow lingers in areas at the higher elevations throughout the summer. Crater Lake National Park is almost entirely surrounded by National forests and wilderness areas. The Winema National Forest borders the park on the south and east, the Umpqua National Forest is along the northern border, the Rogue River National Forest is along the western and southwestern borders, and the Sky Lakes Wilderness Area is along the southern border.

The southern entrance station at Mazama Village is 76 miles from Medford, Oregon, and 56 miles from Klamath Falls, Oregon, on State Highway 62. The park can be accessed from the north by State Highway 138. Both the south and north access roads lead to Rim Drive, a 33-mile roadway that circles the caldera rim with pullouts that provide scenic views of the lake. Winter access is maintained only from the southern entrance to the park headquarters in Munson Valley and up to Rim Village. Road closures, particularly between the headquarters and the rim, are common in winter because of frequent snowstorms.

Rim Village is on the southern side of the caldera rim. It is at an elevation of 2,164 meters (7,100 feet). It has been in operation year round since 1948, with limited services in winter. Seasonal interpretive activities are provided at a small visitor facility near the rim and at the Sinnott Memorial overlook. Sinnott Memorial is 25 feet below the rim on a precipitous cliff overlooking the lake. It is significant architecturally because it is constructed mostly of large, uncoursed rock that blends into the wall of the rim. The memorial offers visitors a spectacular view of Crater Lake and is an ideal place from which to study the lake and caldera. Seasonal hotel accommodations are available at Crater Lake Lodge. Food, gifts, a picnic area, geology talks (summer only), and interpretive exhibits also are available at Rim Village.

The headquarters of the park is about 3 miles south of Rim Village, in Munson Valley. The headquarters serves as the center for administration and maintenance of the park and for housing of the National Park Service employees. The Steel Information Center at the headquarters serves as a year-round interpretation and orientation focal point for visitors. The headquarters is in an historic complex of buildings with a designed landscape. This complex was constructed over a 15-year period beginning in 1926. The historic buildings at the headquarters and at Rim Village are listed in the National Register of Historic Places.

Mazama Village is about 7 miles south of Rim Village, and it is the primary overnight use area in summer. A campground, motel accommodations, food services, a gas station, a camper service store, shower and laundry facilities, interpretive walks, and evening campfire programs are provided at Mazama Village.

The Cleetwood area, on the northern side of the caldera rim, is accessed from Rim Drive. It is about 6 miles east of the north junction of Rim Drive and the north entrance road. From the parking lot at the Cleetwood area, a walking trail descends down the side of the caldera to the lake, a drop of 800 vertical feet. Commercial boat tours of the lake are available from this area. Naturalists from the National Park Service accompany the tours.


The park is in a complex geologic region of the Cascade Range, in Southern Oregon. Mount Mazama, which is about 400,000 years old, is one of the younger generation volcanoes in the Cascade Range (Bacon and others, 1997). Mount Mazama formed in an area of older andesitic volcanoes. The older generation volcanoes are represented in the park by the weathered remnants of Union Peak and Timber Crater. These volcanoes were active about 1.2 million years ago, and they have undergone extensive erosion by water and ice. The less resistant ash and breccia deposits of the upper portions of the volcanoes have been eroded away leaving a central spire that formed from the resistant rock of the core plug and the surrounding andesite lava flows.

Mount Mazama formed as a result of five closely spaced volcanic vents that produced a composite cone. Three volcanic vents are within the present-day caldera, and the other two are Mount Scott to the east and Williams Crater to the west. Regular eruptions of pumice, ashflows, and lava flows of andesite and dacite produced a peak reaching 10,000 to 12,000 feet in elevation. About 7,700 years ago, a major eruption covered much of Oregon and the rest of the Northwest with a layer of pumice and ash. Near the mountain, pyroclastic ash and cinder avalanches covered much of the flanks and nearby lowlands (Bacon and others, 1997). The massive eruption emptied the magma chamber under Mount Mazama, and the mountain collapsed. This collapse formed a caldera that is about 4,000 feet deep. The caldera has partially filled with water, creating the spectacular Crater Lake. Approximately 7,400 years ago, eruptions within the caldera formed several cones. One of these is called Wizard Island, which is visible above the lake.

The present landscape is dominated by the lakefilled caldera and the pumice- and ash-covered flanks of truncated Mount Mazama. Exposed in and around the caldera is andesitic and dacitic bedrock from previous eruptions. The ash, cinders, and pumice ejected from the mountain produced landscapes with characteristics related to the relative size and amount of these deposits. The initial eruption produced a plume of pumice and ash that covered a large portion of Oregon and the rest of the Northwest. The finer, sand-sized pumice and ash in the park is mainly on the drier part of the eastern flank of Timber Crater. This airfall material also produced thick accumulations of gravel-sized pumice to the north and east of Mount Mazama. The first pumice and ash pyroclastic flows, which traveled within the park and far beyond its boundaries, were mainly restricted to the valleys and the low-lying lava plains. These thick flows typically were dominated by cobble-sized pumice. Cross-sections of these flows can be seen in truncated stream terraces and roadcut embankments to the west of the park. During later eruptions, the ashflows were of smaller extent and were dominated by ash and cinders and a smaller percentage of pumice. These flows, on the outer flanks of the caldera, partially covered and filled in around the andesite and dacite bedrock (Williams, 1942). Today, the layered ashflows can be seen in the steep downcut canyonsides of Castle, Annie, Sand, and Sun Creeks.

Somewhat overshadowed by the effects of the volcanic eruptions is the long history of glaciation in the park. During the height of the Ice Age, large icecaps covered most the Cascade Range. Valley glaciers were on Mount Mazama throughout its pre-eruption history. Between eruptions, the mountain commonly had many valley glaciers. Slowly, large valleys were carved out by the glaciers. Some of these valleys were totally or partially filled in by tephra, particularly those on the northern side of Mount Mazama.

The cataclysmic eruption of Mount Mazama occurred during a period that was warmer than the present climate and in which the valley glaciers had retreated beyond the present caldera rim. The collapse of the mountain truncated the glacial valleys, and most of the glacial deposits in the valleys have been incorporated into or covered by eruption debris. Remnants of deposits from the icecaps remain, however, mainly in areas upwind of the airfall deposits and at elevations high enough to escape burial by the ashflows. These remnants lie to the west and south, near the border of the park. They consist of the oldest parent material in the park, the ice having receded about 15,000 to 25,000 years ago (Harris, 1988).

Detailed descriptions of ongoing geologic investigations within the park can be obtained from the Crater Lake Data Clearinghouse website maintained by the U.S. Geological Survey (Anonymous, 2000). (http://craterlake.wr.usgs.gov)


Prepared by the Natural Resources Conservation Service, National Water and Climate Center, Portland, Oregon.

The climate tables for this survey were created from data collected at the climate station at the headquarters of Crater Lake National Park, Oregon.

Thunderstorm days, relative humidity, percent sunshine, and wind information were estimated from data collected at the First Order station at Medford, Oregon, and from upper air data.

Table 1 gives data on temperature and precipitation for the park as recorded at Crater Lake in the period 1971 to 2000. Table 2 shows probable dates of the first freeze in fall and the last freeze in spring. Table 3 provides data on the length of the growing season. The extremes given in this section are for the entire period of record, which is 1931 to 2000.

In winter, the average temperature is 26.5 degrees F and the average daily minimum temperature is 18.4 degrees. The lowest temperature on record, which occurred at Crater Lake on January 21, 1962, was -21 degrees. In summer, the average temperature is 51.1 degrees and the average daily maximum temperature is 64.5 degrees. The highest temperature, which occurred at Crater Lake on August 8, 1981, was 90 degrees.

Growing degree days are shown in table 1. They are equivalent to “heat units.” During the month, growing degree days accumulate by the amount that the average temperature each day exceeds a base temperature (40 degrees). The normal monthly accumulation is used to schedule single or successive plantings of a crop between the last freeze in spring and the first freeze in fall.

The average annual precipitation is about 66.88 inches at the park headquarters. The average annual precipitation varies significantly across the park. Most of the western half of the park receives about 60 to 70 inches of precipitation annually. East of the rim, precipitation declines rapidly, with the northeastern corner of the park receiving only about 35 to 45 inches annually. Only about 2 inches, or 3 percent, of the annual total falls during the frost-free period in July and August. The frost-free season typically is only about 40 days, from mid-July to mid-August. The heaviest 1-day rainfall during the period of record was 7.3 inches on June 12, 1950. Thunderstorms occur on about 15 days each year, and most occur in May through August.

The average seasonal snowfall at the park headquarters is 482.7 inches, but it is higher along the rim. The average snowfall decreases to the northeast; the lowest amounts typically are in the northeastern corner of the park. The greatest snow depth at any one time during the period of record was 252 inches recorded on April 3, 1983. On an average, 234 days per year have at least 1 inch of snow on the ground

The heaviest 1-day snowfall on record is 37 inches recorded on February 28, 1971. Snowfall has been recorded in every month, and in some years snow has remained on the ground until August in the coolest, shaded areas.

The average relative humidity in midafternoon is about 40 percent. Humidity is highest at night, and the average at dawn is about 80 percent. The sun shines about 80 percent of the time possible in summer and about 45 percent of the time in winter. The prevailing wind is from the west. The average windspeed is highest, about 15 miles per hour, in winter and early in spring. The windspeed varies significantly, depending upon local topography. The windspeed is highest over exposed ridges, such as in the western and eastern high-lying areas of the rim.

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