Mount Mazama lies in Klamath County, within the U.S. state of Oregon, 60 miles (97 km) north of the border between Oregon and California. It lies in the southern portion of the Cascade Range. Crater Lake sits partly inside the volcano's caldera, with a depth of 1,943 feet (592 m)[a]; it thus represents the deepest body of freshwater in the United States and the second deepest in North America after Great Slave Lake in Canada. Before its caldera-forming eruption, Mazama stood at an elevation between 10,800 to 12,100 feet (3,300 to 3,700 m), placing it about 1 mile (1.6 km) above the lake and making it Oregon's highest peak. The Global Volcanism Program currently lists its elevation at 8,157 feet (2,486 m), while the Geographic Names Information System provides an elevation of 6,174 feet (1,882 m).
Crater Lake National Park
Crater Lake National Park covers an area of 250 square miles (650 km2), including forest areas, alpine terrain, the Crater Lake, and the vast majority of Mount Mazama. A wilderness area, it was dedicated in 1902 and is overseen by the National Park Service. It receives about 500,000 visitors each year, and these tourists can go hiking, take bike, ranger-guided, and trolley tours, swim, fish, camp, and participate in other recreational activities. While the Park area remains open throughout the year, certain roads and facilities close in the winter season.
Crater Lake, formed in the caldera from Mazama's collapse
Glaciers formed on the mountain over and over as Mazama developed. They carved trenches in the flanks of the volcano in addition to U-shaped valleys under the base of the volcanic cone. These can be observed at three large glacial canyons on its southern slopes: Kerr Notch, Munson Balley, and Sun Notch. Whenever eruptions took place in the presence of ice, lava was chilled by glaciers, creating glassy talus deposits. Sometimes, the lava coursed into areas previously carved by glaciers like at Sentinel Rock, filling canyons with volcanic rock. Moraines occur up to 17 miles (27 km) from the rim of Mazama's caldera and there are glacial striations visible at several sites in the area. When the climactic eruption occurred, the climate was warm and dry, and the most recent period of glacial advance ceased about 27,000 years ago, so by the time Mazama collapsed, ice was likely only present at higher elevations. Using argon geochronology and paleoclimatic records, scientists have identified that the Sand Creek, Sun Creek, and Annie Creek canyons were carved by the advance of ice over lava flows, pushing debris towards Klamath Marsh and Klamath Graben or nearby rivers. A glacial cirque can be seen on Mount Scott's northwestern flank, and glacial till occurs on Mazama's slopes, especially on the western slopes and at lower elevations. Till and fluvial sediments occur in the caldera walls, forming particularly thick deposits under Roundtop and Wineglass. Many lava flows that were glaciated have since been covered by more recent lava flows.
Crater Lake formed from a network of lakes and ponds, eventually reaching a depth of 1,949 feet (594 m). Lake levels rose while the Wizard Island landform inside the crater was forming. Water interacted with lava flows to form pillow lava. Because of climate change patterns over time, Crater Lake's surface level has changed, dropping as much as 40 feet (12 m) for example at the beginning of the 1900s. Now the water from precipitation nearly equals water lost to evaporation and drainage, with most leakage taking place at the Wineglass deposit at the northern side of the crater, without which the lake would likely have overflowed at the northern side.
Average snowfall in the Crater Lake area has been decreasing since the 1930s. Crater Lake's mean surface water temperatures have increased about 5 °F (3 °C) since the 1960s. Though this may eventually cause algae to grow and obscure the water, Crater Lake remains one of the cleanest bodies of water in the world.