Mount Mazama is a destroyed stratovolcano in the Oregon part of the Cascade Volcanic Arc and the Cascade Range located in the United States. The volcano’s collapsed caldera holds Crater Lake, and the entire mountain is located within Crater Lake National Park.
Mazama was destroyed by a volcanic eruption that occurred around 5,677 (± 150) BC.[1][3] The eruption reduced Mazama’s approximate 12,000-foot (3,700 m) height by around a mile (1600 m). Much of the volcano fell into the volcano’s partially emptied neck and magma chamber. At 8,159 feet (2,487 m), Hillman Peak is now the highest point on the rim.
Location
Crater Lake occupies a basin in Mount Mazama, one of the volcanoes that make up the Cascades Mountain Range along the west coast of the United States. The major volcanoes of the Cascades include the following (listed from south to north):
California: Lassen Peak and Mount Shasta.
Oregon: Mount Mazama, Three Sisters, Mount Jefferson, and Mount Hood.
Washington: Mount Saint Helens, Mount Adams, Mount Rainier, Glacier Peak, and Mount Baker.
Crater Lake caldera formed by collapse during the catastrophic eruption of approximately 50 cubic kilometers of magma, 6,845 carbon-14 years B.P. (before present). The 8×10 kilometer caldera lies in the remains of Mount Mazama, a Pleistocene stratovolcano cluster covering 400 square kilometers in the southern Oregon Cascades. Prior to its climactic eruption, Mount Mazama’s summit had an elevation between 3,300 meters and 3,700 meters (10,800 – 12,000 feet). Its southern and southeastern flanks were deeply incised by glacial valleys, now beheaded, that form U-shaped notches in the caldera wall.
Mazama was one of the major volcanoes of the High Cascades and is the largest edifice between Mount Shasta and the Three Sisters volcanoes. Around Mazama are monogenetic cinder cones, lava fields, and small shield volcanoes that produced calc-alkaline basalt and andesite, primitive tholeiite, and rare shoshonitic andesite. These range in age from around 600,000 years to perhaps 40,000 years ago, and are similar to monogenetic volcanoes up and down the High Cascades.
Individual stratovolcanoes and shields that make up Mount Mazama become younger in a west-northwest sense. The oldest Mazama lavas dated are flows near lake level at Phantom Ship and the lavas of Mount Scott (around 400,000 years). The youngest stratovolcano is Hillman Peak (around 70,000 years). Local andesite flows on the north rim are 50-40,000 years old.
Mount Mazama, Crater Lake national Park,Oregon, USA
Post-caldera volcanic landforms are present beneath the lake surface and poke through to form Wizard Island. The central platform, Merriam Cone, and Wizard Island are all andesite evidently erupted within a few hundred years of caldera collapse. The small rhyodacite dome 30 meters belows lake level one kilometer east of Wizard Island is the youngest feature
Mt. Mazama & Crater Lake
Mt. Mazama is located in the southern part of the Cascade Range, about sixty miles north of the Oregon-California state line. It holds Crater Lake (giiwas in the Klamath language), at 1,943 feet the deepest freshwater body of water in the United States. Much of the mountain is a caldera formed by a massive volcanic eruption and collapse after the magma chamber emptied tons of material over a wide area. This climactic event, which took place about 7,700 years ago, was more than forty times as powerful as the eruption of Mt. St. Helens in 1980. Mazama ash is so extensive that it represents a time marker throughout the Pacific Northwest, as the light-colored band is readily recognizable in relation to other strata.
Because Mt. Mazama holds Crater Lake, it has been cited as a classic example of how small calderas evolve. The oldest lavas assigned to it are those resulting from a cluster of volcanoes that erupted between 400,000 and 420,000 years ago. An example is readily seen in the lake—a cone fragment called Phantom Ship. Mt. Mazama attained a height of 12,140 feet (3,700 meters), and the summit once loomed a mile above the surface of present-day Crater Lake.
Due to the mountain’s growth between and during numerous colder periods, Mt. Mazama supported glaciers over much of its existence. Some were large, such as the three glacial canyons on its south flank—Munson Valley, Sun Notch, and Kerr Notch. The last glacial advance there ended 27,000 years ago. By the time of the mountain’s climactic eruption, when conditions were relatively warm and dry, ice must have been restricted to only the highest elevations.
Mount Mazama, Crater Lake national Park,Oregon, USA
Two precursory events interrupted the more than 20,000 years that Mazama remained dormant. About 8,000 years ago, flows from Llao Rock and associated pumice deposits, followed by the opening of a new vent on Mazama’s north flank, signaled a new and explosive period of activity. This took place while humans occupied at least some of the area around the mountain. To the east, people whose existence is documented through artifacts such as sagebrush sandals became increasingly threatened by both a drier climate and renewed volcanic activity. To the south, Mazama’s eruption disrupted the lives of people sufficiently so that stories about its wrath and after-effects have been passed down from one generation to the next.
The climactic eruption began with a towering column of pumice and ash rising from a vent located northeast of the summit, which resulted in deposits as thick as several centimeters as far away as present-day central Alberta. This phase of the eruption included pyroclastic flows—high speed and super-hot avalanches—that resulted from the vent widening and erupting at an increasing rate. Having drained a large portion of the magma chamber, the volcano lacked a foundation and began to collapse inward. The eruption entered a ring-vent phase, where contents in the magma chamber were forced out through cracks and fractures in a shape roughly corresponding to what later became Crater Lake. Large pyroclastic flows rushed past the mountain’s flanks and onto once-glaciated valleys.
The eruption and collapse, which lasted only a few days, was followed by volcanism restricted to the resulting caldera. Most of the post-caldera volcanism is hidden from view by Crater Lake, with Wizard Island amounting to only 2 percent of the activity that for the most part ceased around 4,800 years ago. The early lake formed from precipitation but also through a hydrothermal system fueled by residual heat from the magma chamber. Crater Lake has some of the purest water known due to the general lack of organic nutrients, and it holds the world record for clarity. Still, its seemingly bucolic state will change in the future as the mountain is reawakened by renewed volcanic activity.
The name Mt. Mazama came from William G. Steel, who is known as the father of Crater Lake National Park and is the founder of the Mazamas, a mountaineering group formed on Mount Hood in 1894. Mazama is among the obsolete names for mountain goat, though it is derived from an Aztec word meaning “small deer.” When geologist Joseph S. Diller of the U.S. Geological Survey was making the first topographic map of the Crater Lake area in 1896, he asked about a name for the mountain that holds the lake. Steel suggested his organization as the namesake, partly because the group’s excursion to Crater Lake that summer had the purpose of promoting national park status for the area.
In August, the Mazamas “christened” the mountain, and Diller and other scientists gave the first interpretive talks to visitors at what later became known as Rim Village. President Theodore Roosevelt signed the Crater Lake National Park bill into law in 1902.
point of Interest
Crater Lake
Generous amounts of winter snow, averaging 533 inches (1,354 cm) per year, supply the lake with water. There are no inlets or outlets to the lake. Crater Lake, at 1,958 feet (597 meters) deep, is the seventh deepest lake in the world and the deepest in the United States. Evaporation and seepage prevent the lake from becoming any deeper. The lake averages more than five miles (8 km) in diameter, and is surrounded by steep rock walls that rise up to 2000 feet (600 meters) above the lake’s surface. — Excerpt from: U.S. National Park Service, Crater Lake National Park Website, 2001
Hillman Peak, Mount Scott, Phantom Ship
Individual stratovolcanoes and shields that make up Mount Mazama become younger in a west-northwest sense. The oldest Mazama lavas dated are flows near lake level at Phantom Ship and the lavas of Mount Scott (around 400,000 years). The youngest stratovolcano is Hillman Peak (around 70,000 years). Local andesite flows on the north rim are 50-40,000 years old. — Excerpt from: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada: Cambridge University Press, 354p., p.193-195, Contribution by Charles R. Bacon
Wizard Island
Following the collapse of Mount Mazama, lava poured into the caldera even as the lake began to rise. Today, a small volcanic island, Wizard Island, appears on the west side of the lake. This cinder cone rises 760 feet (233 meters) above the lake and is surrounded by black volcanic lava blocks. A small crater, 300 feet (90 meters) across and 90 feet (27 meters) deep, rests on the summit. The crater is filled by snow during the winter months, but remains dry during the summer.
Crater Lake was formed after the collapse of an ancient volcano, posthumously named Mount Mazama. This volcano violently erupted approximately 7700 years ago. That eruption was 42 times as powerful as the 1980 eruption of Mount St. Helens. The basin or caldera was formed after the top 5000 feet of the volcano collapsed. Subsequent lava flows sealed the bottom, allowing the caldera to fill with approximately 4.6 trillion gallons of water from rainfall and snow melt, to create the seventh deepest lake in the world at 1,932 feet.
Today, Crater Lake is widely known for its intense blue color and spectacular views. During summer, visitors may navigate the 33-mile Rim Drive around the lake, enjoy boat tours on the lake surface, stay in the historic Crater Lake Lodge, camp at Mazama Village, or hike some of the park’s various trails including Mount Scott at 8,929 feet. Diverse interpretative programs enhance visitors’ knowledge and appreciation of this national park, 90% of which is managed as wilderness. The winter brings some of the heaviest snowfall in the country, averaging 533 inches per year. Although park facilities mostly close for this snowy season, visitors may view the lake during fair weather, enjoy cross-country skiing, and participate in weekend snowshoe hikes.
Crater Lake National Park attracts approximately 500,000 visitors per year, with the high season being July and August. Crater Lake National Park is located in southern Oregon on the crest of the Cascade Range, 100 miles from the Pacific coast. The National Park was established in 1902 and encompases 183,244 square miles. The 33-mile Rim Drive around Crater Lake is a two lane road that has more than 20 scenic overlooks. From mid-October until mid-June, the north entrance and Rim Drive are closed to the public due to deep snow and ice buildups along the road. Rim Drive around the east side of the lake can be closed earlier than mid-October and may not open until July. Deer and other wildlife crossing the road and icy conditions at any time of the year provide hazards to drivers.
Profile
Crater Lake Caldera
Location: Oregon
Latitude: 42.93 N
Longitude: 122.12 W
Height: 2,487 meters (8,156 feet – Hillman Peak)
Type: Caldera
Number of eruptions in the past 200 years: 0
Latest Eruptions: 4,000 years ago … at least 800-900 years ago (Wizard Island).
Present thermal activity: None
Remarks: Largest known eruption from Cascade Range volcano. Catastrophic, caldera-forming eruption 7,000 years ago; post-caldera lava and domes … From a probable altitude of roughly 12,000 feet, the top of former Mount Mazama was lost to eruption and collapse that left the present huge crater and the deepest lake (1,932 feet) in North America. Explosive eruptions built Wizard Island and two other cones (submerged) on present crater floor.