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• 1. [Article] Studies of hydrothermal processes in Crater Lake, OR

  Citation × Citation Citation Abstract Copy Title: Studies of hydrothermal processes in Crater Lake, OR Author: Dymond, Jack, McManus, James, Oregon State University. College of Oceanography, Collier, Robert W. Title: Studies of hydrothermal processes in Crater Lake, OR Author: Dymond, Jack, McManus, James, Oregon State University. College of Oceanography, Collier, Robert W. Close

• 2. [Article] Studies of hydrothermal processes in Crater Lake : a report of field studies conducted in 1988 for the National Park Service

  Citation × Citation Citation Abstract Copy Title: Studies of hydrothermal processes in Crater Lake : a report of field studies conducted in 1988 for the National Park Service Author: Oregon State University. College of Oceanography, Cooperative Park Studies Unit (Corvallis, Or.), Dymond, Jack, Collier, Robert W. Title: Studies of hydrothermal processes in Crater Lake : a report of field studies conducted in 1988 for the National Park Service Author: Oregon State University. College of Oceanography, Cooperative Park Studies Unit (Corvallis, Or.), Dymond, Jack, Collier, Robert W. Close

• 3. [Article] Mount Mazama and Crater Lake : a study of the botanical and human responses to a geologic event

  Crater Lake, located in the southern Cascade mountains of Oregon, is the seventh deepest lake in the world. Unlike a majority of the deepest lakes in the world, found in continental rift valleys, Crater ...

  Citation × Citation Citation Abstract Copy Title: Mount Mazama and Crater Lake : a study of the botanical and human responses to a geologic event Author: Green, Robyn A. Crater Lake, located in the southern Cascade mountains of Oregon, is the seventh deepest lake in the world. Unlike a majority of the deepest lakes in the world, found in continental rift valleys, Crater Lake is in the caldera of a volcano. For the young at heart and mind, those willing to descend (and ascend) about 700 feet to Cleetwood Cove can undertake a boat tour of Crater Lake. From the boat, Crater Lake is more than just a beautiful blue lake; it becomes the inside of a volcano, where the response of people and plants to a geologic event can be investigated. The catastrophic eruption of Mount Mazama 7,700 years ago affected both plant and human populations. Before pumice and ash from the volcano blanketed the landscape like freshly fallen snow, the forests to the east of Mount Mazama were dominated by ponderosa and lodgepole pine. Within the immediate vicinity of the volcano all life was obliterated; the force of the eruptive material toppled vegetation and buried it with ash and pumice. Through the recovery process of succession, life has slowly returned to Crater Lake. Forests surrounding the lake are now dominated by mountain hemlock, whitebark pine, and lodgepole pine. These plants not only depict the process of succession, but also of adaptation to a volcanic environment. Factors restricting establishment and growth of plants are controlled by the nonliving environment. Climate, geologic activities, elevation, and time all contribute to the availability of water, soil, nutrients, and sunlight, which directly affect plant growth. Heavy winter snows, which linger until July, and very little summer rain, control soil moisture and the length of the growing season at Crater Lake. Volcanic activity dictates the parent material, which with time breaks down forming soil. The properties of the soil determine its ability to hold water and the concentrations and availability of nutrients. Pumice soils provide developing plants with low nutrient supplies and affect the growth of plants with extreme surface temperature fluctuations. Volcanic cinder has a very low capacity to hold water and nutrients, thus restricting plant growth. People have lived in the Pacific Northwest for at least the last 10,000 years. Direct archaeological evidence of life near Mount Mazama is scarce. Those occupation sites closest to the volcano were covered with pumice and ash from the climactic eruptions. Sites protected from the eruptive material and sites farther away provide archaeologists a glimpse into the cultures of the Basin and Range Province. People living around Mount Mazama were predominantly nomadic; their survival depended on available resources. The catastrophic eruption of Mount Mazama and the subsequent devastation of the land disrupted their lives. As the environment recovered from the eruption, the people also recovered. They were forced to find alternative food sources, fuels, and shelters. The indigenous people's perceptions of this natural disaster are understood indirectly through the use of archaeological data and folklore. Their stories tell of angry gods and stalwart ancestors. Llao, the God of the underworld, and Skell, the God of light, were often at war, Llao from Mount Mazama and Skell from Mount Shasta. Although the origins of such legends are difficult to trace, they emphasize the perceptions of those who lived in the shadow of this mystical volcano. People's limited understanding of the volcano thus triggered their reverence for the place. Title: Mount Mazama and Crater Lake : a study of the botanical and human responses to a geologic event Author: Green, Robyn A. Crater Lake, located in the southern Cascade mountains of Oregon, is the seventh deepest lake in the world. Unlike a majority of the deepest lakes in the world, found in continental rift valleys, Crater Lake is in the caldera of a volcano. For the young at heart and mind, those willing to descend (and ascend) about 700 feet to Cleetwood Cove can undertake a boat tour of Crater Lake. From the boat, Crater Lake is more than just a beautiful blue lake; it becomes the inside of a volcano, where the response of people and plants to a geologic event can be investigated. The catastrophic eruption of Mount Mazama 7,700 years ago affected both plant and human populations. Before pumice and ash from the volcano blanketed the landscape like freshly fallen snow, the forests to the east of Mount Mazama were dominated by ponderosa and lodgepole pine. Within the immediate vicinity of the volcano all life was obliterated; the force of the eruptive material toppled vegetation and buried it with ash and pumice. Through the recovery process of succession, life has slowly returned to Crater Lake. Forests surrounding the lake are now dominated by mountain hemlock, whitebark pine, and lodgepole pine. These plants not only depict the process of succession, but also of adaptation to a volcanic environment. Factors restricting establishment and growth of plants are controlled by the nonliving environment. Climate, geologic activities, elevation, and time all contribute to the availability of water, soil, nutrients, and sunlight, which directly affect plant growth. Heavy winter snows, which linger until July, and very little summer rain, control soil moisture and the length of the growing season at Crater Lake. Volcanic activity dictates the parent material, which with time breaks down forming soil. The properties of the soil determine its ability to hold water and the concentrations and availability of nutrients. Pumice soils provide developing plants with low nutrient supplies and affect the growth of plants with extreme surface temperature fluctuations. Volcanic cinder has a very low capacity to hold water and nutrients, thus restricting plant growth. People have lived in the Pacific Northwest for at least the last 10,000 years. Direct archaeological evidence of life near Mount Mazama is scarce. Those occupation sites closest to the volcano were covered with pumice and ash from the climactic eruptions. Sites protected from the eruptive material and sites farther away provide archaeologists a glimpse into the cultures of the Basin and Range Province. People living around Mount Mazama were predominantly nomadic; their survival depended on available resources. The catastrophic eruption of Mount Mazama and the subsequent devastation of the land disrupted their lives. As the environment recovered from the eruption, the people also recovered. They were forced to find alternative food sources, fuels, and shelters. The indigenous people's perceptions of this natural disaster are understood indirectly through the use of archaeological data and folklore. Their stories tell of angry gods and stalwart ancestors. Llao, the God of the underworld, and Skell, the God of light, were often at war, Llao from Mount Mazama and Skell from Mount Shasta. Although the origins of such legends are difficult to trace, they emphasize the perceptions of those who lived in the shadow of this mystical volcano. People's limited understanding of the volcano thus triggered their reverence for the place. Close

• 4. [Article] A new model for the formation of Crater Lake Caldera, Oregon

  During the Pleistocene, an andesitic volcano named Mount Mazama grew to a probable elevation of 3000 meters in south- central Oregon. Near the end of the Pleistocene, three diverse magma types appeared ...

  Citation × Citation Citation Abstract Copy Title: A new model for the formation of Crater Lake Caldera, Oregon Author: Lidstrom, John Walter During the Pleistocene, an andesitic volcano named Mount Mazama grew to a probable elevation of 3000 meters in south- central Oregon. Near the end of the Pleistocene, three diverse magma types appeared in the eruptive products associated with Mount Mazama: l)High-alumina basaltic andesite magma associated with an early plateau and with coeval cinder cones; 2) Hypersthene andesite magma similar in composition to the andesite which had formed the main cone; 3) Dacite magma, erupted both as pyroclastic material and as flank lava flows after formation of the andesitic cone. Approximately 12, 000-13, 000 years ago, eruption of andesite and then dacite occurred along a semicircular fracture now represented by the north wall of the caldera. The eruption of dacite was a surface expression of a shallow chamber of dacite magma emplaced beneath Mount Mazama. Before and after emplacement of the dacite magma chamber, basaltic andesite erupted upon the lower flanks and plateau surrounding the volcano, The last such parasitic activity occurred at Forgotten Crater (on the western flank of Mount Mazama) where lava and pumice of intimately mixed dacite and basaltic andesite appeared. Approximately 6600 years ago, explosive eruption of dacite pumice began from central vents. The magma of these initial eruptions was characterized by discrete gas nuclei which expanded rapidly, disrupted the enclosing liquid into fine ash, and provided the energy to propel this ash high above the summit. As eruption proceeded, magma was tapped in which gas nuclei were actively forming and were thoroughly dispersed through the magma. At this stage, the erupted material behaved as a fluidized mass, frothed over the crater rim, and rushed down the slopes as glowing avalanches. Immediately following eruption of fluidized dacite, a more mafic magma was erupted in the form of basic scoria flows. This basic scoria was chemically, similar to par3sitic eruptions of basaltic andesite, and was not nearly as mobile as the earlier dacite ash-flows. The waning stages of eruption were characterized by crystal-rich basic scoria containing abundant fragments of andesite and granodiorite. Following the eruption of crystal- and lithic-rich basic scoria, the summit of Mount Mazama collapsed into the underlying magma chamber, producing the Crater Lake caldera. Soon after collapse, eruption of mafic magma occurred on the caldera floor, probably forming a lava lake. The last eruption formed an intra-caldera andesitic cone called Wizard Island Wizard Island lavas are chemically similar to the andesites which formed the main cone of Mount Mazama. Thus, a sequence of volcanic activity culminating in violent eruption and collapse, returned to its initial condition. Calculations of Mazama ash volume are presented and it is concluded that there is no discrepancy between volume of missing Mount Mazama and volume of erupted material. Crystal-rich basic scoria flows containing melted granitic fragments (torn from the margins of the dacite magma chamber) indicate that the chamber was essentially emptied during the culminating eruptions. It is suggested that basic scoria magma occupied the bottom portion of the dacite magma chamber. This mafic magma assimilated granodiorite which had crystallized around the margins of the dacite magma. A new model for the formation of the Crater Lake caldera is presented. In this model the magma types recognized at Crater Lake ascended through the crust as independent bodies. Whenever two of these magma types came into marginal contact, limited eruption of mixed magmas was possible. However, prior to the culminating eruptions, a high-temperatures basaltic andesite magma was injected into the lower portion of the volatile-saturated, cooling dacite magma. Energy transferred from the mafic magma triggered exsolution of gas in the silicic magma until vapor pressure exceeded confining pressure. Once eruption began, it did not stop until the chamber was depleted of its gas-rich magma. The Crater Lake caldera was formed when the unsupported summit of Mount Mazama collapsed into this sub-volcanic vacancy. Many other calderas, long recognized as a special (Krakatoan) type, were produced following the eruption of more than one magma. It is suggested that the process described above is an important caldera-forming mechanism. Title: A new model for the formation of Crater Lake Caldera, Oregon Author: Lidstrom, John Walter During the Pleistocene, an andesitic volcano named Mount Mazama grew to a probable elevation of 3000 meters in south- central Oregon. Near the end of the Pleistocene, three diverse magma types appeared in the eruptive products associated with Mount Mazama: l)High-alumina basaltic andesite magma associated with an early plateau and with coeval cinder cones; 2) Hypersthene andesite magma similar in composition to the andesite which had formed the main cone; 3) Dacite magma, erupted both as pyroclastic material and as flank lava flows after formation of the andesitic cone. Approximately 12, 000-13, 000 years ago, eruption of andesite and then dacite occurred along a semicircular fracture now represented by the north wall of the caldera. The eruption of dacite was a surface expression of a shallow chamber of dacite magma emplaced beneath Mount Mazama. Before and after emplacement of the dacite magma chamber, basaltic andesite erupted upon the lower flanks and plateau surrounding the volcano, The last such parasitic activity occurred at Forgotten Crater (on the western flank of Mount Mazama) where lava and pumice of intimately mixed dacite and basaltic andesite appeared. Approximately 6600 years ago, explosive eruption of dacite pumice began from central vents. The magma of these initial eruptions was characterized by discrete gas nuclei which expanded rapidly, disrupted the enclosing liquid into fine ash, and provided the energy to propel this ash high above the summit. As eruption proceeded, magma was tapped in which gas nuclei were actively forming and were thoroughly dispersed through the magma. At this stage, the erupted material behaved as a fluidized mass, frothed over the crater rim, and rushed down the slopes as glowing avalanches. Immediately following eruption of fluidized dacite, a more mafic magma was erupted in the form of basic scoria flows. This basic scoria was chemically, similar to par3sitic eruptions of basaltic andesite, and was not nearly as mobile as the earlier dacite ash-flows. The waning stages of eruption were characterized by crystal-rich basic scoria containing abundant fragments of andesite and granodiorite. Following the eruption of crystal- and lithic-rich basic scoria, the summit of Mount Mazama collapsed into the underlying magma chamber, producing the Crater Lake caldera. Soon after collapse, eruption of mafic magma occurred on the caldera floor, probably forming a lava lake. The last eruption formed an intra-caldera andesitic cone called Wizard Island Wizard Island lavas are chemically similar to the andesites which formed the main cone of Mount Mazama. Thus, a sequence of volcanic activity culminating in violent eruption and collapse, returned to its initial condition. Calculations of Mazama ash volume are presented and it is concluded that there is no discrepancy between volume of missing Mount Mazama and volume of erupted material. Crystal-rich basic scoria flows containing melted granitic fragments (torn from the margins of the dacite magma chamber) indicate that the chamber was essentially emptied during the culminating eruptions. It is suggested that basic scoria magma occupied the bottom portion of the dacite magma chamber. This mafic magma assimilated granodiorite which had crystallized around the margins of the dacite magma. A new model for the formation of the Crater Lake caldera is presented. In this model the magma types recognized at Crater Lake ascended through the crust as independent bodies. Whenever two of these magma types came into marginal contact, limited eruption of mixed magmas was possible. However, prior to the culminating eruptions, a high-temperatures basaltic andesite magma was injected into the lower portion of the volatile-saturated, cooling dacite magma. Energy transferred from the mafic magma triggered exsolution of gas in the silicic magma until vapor pressure exceeded confining pressure. Once eruption began, it did not stop until the chamber was depleted of its gas-rich magma. The Crater Lake caldera was formed when the unsupported summit of Mount Mazama collapsed into this sub-volcanic vacancy. Many other calderas, long recognized as a special (Krakatoan) type, were produced following the eruption of more than one magma. It is suggested that the process described above is an important caldera-forming mechanism. Close