The eruption of Lassen Peak in May 1915 produced four volcanic rock types within 3 days, and the following order: (1) hybrid black dacite lava containing (2) undercooled andesitic inclusions, (3) compositionally banded pumice with dark andesite light bands, (4) unbanded dacite. All represent stages a complex mixing process between basaltic that was interrupted by eruption. They contain disequilibrium phenocryst assemblages characterized coexistence magnesian olivine quartz reacted unreacted...

Research Article| November 01, 2010 Zircon reveals protracted magma storage and recycling beneath Mount St. Helens Lily L. Claiborne; Claiborne 1Department of Earth Environmental Sciences, Vanderbilt University, Nashville, Tennessee 37240, USA Search for other works by this author on: GSW Google Scholar Calvin F. Miller; Miller Daniel M. Flanagan; Flanagan Michael A. Clynne; Clynne 2Volcano Hazards Team, U.S. Geological Survey, Menlo Park, California 94025, Joseph Wooden 3Department Stanford...

Abstract The collapse of a volcanic flank can be destructive and deadly. Hydrothermal alteration is common to volcanoes worldwide thought promote volcano instability by decreasing rock strength. However, some laboratory studies have shown that not all reduces Our new data for altered rhyodacites from Chaos Crags (Lassen center, California, USA) show pore- crack-filling mineral precipitation reduce porosity permeability increase strength, Young's modulus, cohesion. A significant reduction in...

The silicic lava domes of Chaos Crags in Lassen Volcanic National Park contain a suite variably quenched, hybrid basaltic andesite magmatic inclusions. inclusions represent thorough mixing between rhyodacite and basalt recharge liquids accompanied by some mechanical disaggregation the resulting crystals into host preserved quenching on dome emplacement. 87Sr/86Sr ratios (∼0.7037–0.7038) are distinctly lower than those (∼0.704–0.7041), which used to fingerprint origin mineral components...

Eighteen years after dome-forming eruptions ended in 1986, and with little warning, Mount St. Helens began to erupt again October 2004. During the ensuing two years, volcano extruded more than 80×106 m3 of gas-poor, crystal-rich dacite lava. The 2004-6 is remarkably uniform bulk-rock composition and, at 65 percent SiO2 , among richest silica most depleted incompatible elements magmas erupted during past 500 years. Since shortly first spine lava appeared, samples have been collected using a...

Zircon ages and trace element compositions from recent silicic eruptions in the Lassen Volcanic Center (LVC) allow for an evaluation of timing conditions rejuvenation (reheating mobilization crystals) within LVC magmatic system. The is southernmost active Cascade volcano and, prior to 1980 eruption Mount St. Helens, was site only arc during last century. three most were very small moderate-sized lava flows domes dacite (1915 27 ka Peak) rhyodacite (1.1 Chaos Crags). These produced mixed...

The majority of felsic rocks from composite centers in the southernmost Cascades have geochemical and Sr, Nd Pb isotopic ratios that suggest derivation by partial melting lower crust is compositionally similar to calc-alkaline basalts observed region. Only a few δ18O compositions indicate interaction with upper crust. Mineralogical differences among magmas result primarily under variable f(H2O) temperature conditions. Partial low high conditions leaves an amphibole-poor residuum, produces...

Products of the 1915 Lassen Peak eruption reveal evidence for a magma recharge–magma mixing event that may have catalyzed and from which four compositional members were identified: light dacite, black andesitic inclusion, dark andesite. Crystal size distribution, textural, in situ chemical (major trace element Sr isotope) data plagioclase these products define three crystal populations distinct origins: phenocrysts (long axis > 0·5 mm) typically core An contents between 34 36 mol %,...

We have analyzed the heat and mass demands of a petrologic model basalt‐driven magmatic evolution in which variously fractionated mafic magmas mix with silicic partial melts lower crust. formulated steady state budgets for two volcanically distinct areas Lassen region: large, late Quaternary, intermediate to volcanic center nearby, coeval, less evolved Caribou field. At field, provided by cooling fractional crystallization 52 km 3 basalt is more than sufficient produce 10 rhyolitic melt...

vermicular to cuneiform (Barker, 1970).Typically, the Granophyric blocks within late-Pleistocene pyroclastic flow ejecta from Alid volcanic center, northeast Africa, are rapidly groundmass feldspars radiate off pre-existing feldspar crystallized, intrusive equivalent of pumice flow.phenocrysts, with which they in optical continuity Phenocryst compositions and geochemical characteristics (Dunham, 1965).Some workers prefer term granophyre virtually identical.Silicate melt inclusions...

Magmatic evolution at the Lassen volcanic center (LVC) is characterized by a transition from predominantly andesitic to silicic volcanism with time. Magmas of andesitic, or “Brokeoff phase” range in composition basaltic andesite io dacite, whereas those silicic, “Lassen rhyolite. The compositions magmas each phase define well organized but distinct variation trends. Compared Brokeoff‐phase similar SiO 2 content, most Lassen‐phase contain lower concentrations incompatible minor and trace...

The Lassen volcanic center is the most recent of several long‐lived centers in southernmost Cascade Range. These have erupted products ranging from basaltic andesite to rhyolite and are superimposed on a background regional andesitic volcanism. evolution described three stages. Stages I II comprise Brokeoff volcano, 80 km 3 stratocone, active 600 400 ka. volcano compositionally equivalent volcanism region result structurally controlled focusing diffuse mafic magmatism. Stage III comprises...

Hundreds of short‐lived, small‐ to moderate‐volume, mostly mafic volcanoes occur throughout the Lassen region NE California and surround five longer‐lived, large‐volume, intermediate silicic volcanic centers younger than 3 Ma. Volcanic rocks older 7 Ma are scarce in region. We identify 537 vents Ma, we classify these into age intervals compositional categories based on SiO 2 content. Maps by composition illustrate regionally representative trends. By eastern limit voicanism had contracted...

We report the results of recent geologic mapping and radiometric dating that add considerable detail to our understanding eruptive history Mount St. Helens before its latest, or Spirit Lake, stage. New data reevaluation earlier work indicate at least two periods during earliest, Ape Canyon, stage, possibly separated by a long hiatus: one about 300-250 ka second 160–35 ka. Volcanism this stage included eruption biotite- quartz-bearing dacite domes pyroclastic flows in area west beneath...

The geologic map of Lassen Volcanic National Park (LVNP) and vicinity encompasses 1,905 km2 at the south end Cascade Range in Shasta, Lassen, Tehama, Plumas Counties, northeastern California (fig. 1, sheet 3). park includes 430 scenic volcanic features, glacially sculpted terrain, most spectacular array thermal features Range. Interest preserving wonders area as a national arose early 1900s to protect it from commercial development led establishment 1907 two small monuments centered on Peak...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolubility of some alkali and alkaline earth chlorides in water at moderate temperaturesM. A. Clynne R. W. Potter IICite this: J. Chem. Eng. Data 1979, 24, 4, 338–340Publication Date (Print):October 1, 1979Publication History Published online1 May 2002Published inissue 1 October 1979https://pubs.acs.org/doi/10.1021/je60083a019https://doi.org/10.1021/je60083a019research-articleACS PublicationsRequest reuse permissionsArticle...