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C.D. Miller

Publications and source records attributed to C.D. Miller.

10 recordsLinked to original sources
USGS2012

Post-11,000-year volcanism at Medicine Lake Volcano, Cascade Range, northern California

Eruptive activity during the past 11,000 years at Medicine Lake volcano has been episodic. Eight eruptions produced about 5.3 km 3 of basaltic lava during an interval of a few hundred years about 10,500 years B.P. After a hiatus of about 6000 years, eruptive activity resumed with a small andesite eruption at about 4300 years B.P. Approximately 2.5 km 3 of lava with compositions ranging from basalt to rhyolite vented in nine eruptions during an interval of about 3400 years in late Holocene time. The most recent eruption occurred about 900 years B.P. A compositional gap in SiO 2 values of erupted lavas occurs between 58 and 63%. The gap is spanned by chilled magmatic inclusions in late Holocene silicic lavas. Late Holocene andesitic to rhyolitic lavas were probably derived by fractionation, assimilation, and mixing from high-alumina basalt parental magma, possibly from basalt intruded into the volcano during the early mafic episode. Many basaltic to andesitic lavas contain iron-rich crystals and have high FeO*/MgO (characteristics caused by mixing of high-alumina basalt with ferrobasalt liquid produced by fractionation of parental high-alumina basalt). When ferrobasalt and high-alumina basalt are contaminated with a granitic crustal component, a calc-alkaline trend is produced. Some eruptions have produced both tholeiitic and calc-alkaline compositions. The eruptive activity is probably driven by intrusions of basalt that occur during east-west stretching of the crust in an extensional tectonic environment. Vents are typically aligned parallel or subparallel to major structural features, most commonly within 30° of north. Intruded magma should provide adequate heat for commercial geothermal development if sufficient fluids can be found. The nature and timing of future volcanic activity cannot be predicted from the observed pattern, but eruptions high on the edifice could produce high-silica products that might be accompanied by explosive activity, whereas eruptions lower on the flanks are likely to vent more fluid mafic lavas.

Journal of Geophysical Research Solid Earth↗
USGS1995

The USGS/OFDA Volcano Disaster Assistance Program

An erupting volcano is one of nature's truly spectacular sights. From a distance, or perhaps through the cameras of the news media, we often observe roiling mushroom clouds of ash or flows of incandescent lava issuing from the volcano's throat. If, however, you happen to live near that erupting volcano, your life or livelihood may be endangered and your property at risk of destruction a spectacle of power and beauty may become one of fear and devastation. To help mitigate the effects of volcanic eruptions around the world, the U.S. Geological Survey (USGS) and the U.S. Agency for International Development's Office of Foreign Disaster Assistance (OFDA) have developed the Volcano Disaster Assistance Program.

Open-File Report↗
USGS1993

Preventing volcanic catastrophe; the U.S. International Volcano Disaster Assistance Program

When the seismograph began to record the violent earth-shaking caused by yet another eruption of the Nevado del Ruiz volcano in Colombia, no one thought that a few hours later more than 23,000 people would be dead, killed by lahars (volcanic debris flows) in towns and villages several tens of kilometers away from the volcano. Before the fatal eruption the volcano was being monitored by scientists at a seismic station located 9 km from the summit, and information about the volcano's activity was being sent to Colombian emergency-response coordinators who were charged with alerting the public of the danger from the active volcano. Furthermore, area known to be in the pathways lahars had already been identified on maps and communities at risk had been told of their precarious locations. Unfortunately, a storm on November 13, 1985, obscured the glacier-clad summit of Nevado del Ruiz. On that night an explosive eruption tore through the summit and spewed approximately 20 million cubic meters of hot ash and rocks across the snow-covered glacier. These materials were transported across the snow pack by avalanches of hot volcanic debris (pyroclastic flows) and fast-moving, hot, turbulent clouds of gas and ash (pyroclastic surges). The hot pyroclastic flows and surges caused rapid melting of the snow and ice and created large volumes of water that swept down canyons leading away from the summit. As these floods of water descended the volcano, they picked up loose debris and soil from the canyon floors and walls, growing both in volume and density, to form hot lahars. In the river valleys farther down the volcano's flanks, the lahars were as much as 40 m thick and traveled at velocities as fast as 50 km/h. Two and a half hours after the start of the eruption one of the lahars reachered Armero, 74 km from the explosion crater. In a few short minutes most of the town was swept away or buried in a torrent of mud and boulders, and three quaters of the townspeople perished.

Nevado del Ruiz↗
USGS1990

Volcanic hazards in the Pacific Northwest

The Cascade Range stretches from southwestern British Columbia to northern California; the Range consists of major composite volcanic centres, most of which have been active during late Pleistocene and Holocene time. In addition, thousands of smaller basaltic or basaltic-andesite volcanoes have been active during the past few million years. Flowage and tephra hazards associated with future eruptions of composite volcanoes in the Range will endanger communities located within about 50 km of erupting volcanoes. Significant effects will extend to still greater distances downwind from the volcanoes and along stream valleys that head at the volcanoes. Volcanic-hazard assessments and hazard-zonation maps developed for volcanoes in the Range can be used by authorities for long-range land-use planning and provide information to help mitigate the effects of future eruptions. -Author

Geoscience Canada↗