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Michael A. Clynne

Publications and source records attributed to Michael A. Clynne.

54 records · Page 3Linked to original sources
USGS2010

Geologic map of Lassen Volcanic National Park and vicinity, California

The geologic map of Lassen Volcanic National Park (LVNP) and vicinity encompasses 1,905 km 2 at the south end of the Cascade Range in Shasta, Lassen, Tehama, and Plumas Counties, northeastern California (fig. 1, sheet 3). The park includes 430 km 2 of scenic volcanic features, glacially sculpted terrain, and the most spectacular array of thermal features in the Cascade Range. Interest in preserving the scenic wonders of the Lassen area as a national park arose in the early 1900s to protect it from commercial development and led to the establishment in 1907 of two small national monuments centered on Lassen Peak and Cinder Cone. The eruptions of Lassen Peak in 1914-15 were the first in the Cascade Range since widespread settling of the West in the late 1800s. Through the printed media, the eruptions aroused considerable public interest and inspired renewed efforts, which had languished since 1907, to establish a national park. In 1916, Lassen Volcanic National Park was established by combining the areas of the previously established national monuments and adjacent lands. The southernmost Cascade Range is bounded on the west by the Sacramento Valley and the Klamath Mountains, on the south by the Sierra Nevada, and on the east by the Basin and Range geologic provinces. Most of the map area is underlain by middle to late Pleistocene volcanic rocks; Holocene, early Pleistocene, and late Pliocene volcanic rocks (<3.5 m.y.) are less common. Paleozoic and Mesozoic rocks are inferred to underlie the volcanic deposits (Jachens and Saltus, 1983), but the nearest exposures of pre-Tertiary rocks are 15 km to the south, 9 km to the southwest, and 12 km to the west. Diller (1895) recognized the young volcanic geology and produced the first geologic map of the Lassen area. The map (sheet 1) builds on and extends geologic mapping by Williams (1932), Macdonald (1963, 1964, 1965), and Wilson (1961). The Lassen Peak area mapped by Christiansen and others (2002) and published in greater detail (1:24,000) was modified for inclusion here. Figure 2 (sheet 3) shows the mapping credit for previous work; figure 3 (sheet 3) shows locations discussed throughout the text. A CD-ROM entitled Database for the Geologic Map of Lassen Volcanic National Park and Vicinity, California accompanies the printed map (Muffler and others, 2010). The CD-ROM contains ESRI compatible geographic information system data files used to create the 1:50,000-scale geologic map, both geologic and topographic data and their associated metadata files, and printable versions of the geologic map and pamphlet as PDF formatted files. The 1:50,000-scale geologic map was compiled from 1:24,000-scale geologic maps of individual quadrangles that are also included in the CD-ROM. It also contains ancillary data that support the map including locations of rock samples selected for chemical analysis (Clynne and others, 2008) and radiometric dating, photographs of geologic features, and links to related data or web sites. Data contained in the CD-ROM are also available on this Web site. The southernmost Cascade Range consists of a regional platform of basalt and basaltic andesite, with subordinate andesite and sparse dacite. Nested within these regional rocks are 'volcanic centers', defined as large, long-lived, composite, calc-alkaline edifices erupting the full range of compositions from basalt to rhyolite, but dominated by andesite and dacite. Volcanic centers are produced by the focusing of basaltic flux from the mantle and resultant enhanced interaction of mafic magma with the crust. Collectively, volcanic centers mark the axis of the southernmost Cascade Range. The map area includes the entire Lassen Volcanic Center, parts of three older volcanic centers (Maidu, Dittmar, and Latour), and the products of regional volcanism (fig. 4, sheet 3). Terminology used for subdivision of the Lassen Volcanic Center has been modified from Clynne (1984, 1990).

California↗
USGS2008

Radiocarbon dates from volcanic deposits of the Chaos Craigs and Cinder Cone eruptive sequences and other deposits, Lassen Volcanic National Park and vicinity, California

This contribution reports radiocarbon ages obtained from charcoal, wood and other samples collected between 1979 and 2001 in Lassen Volcanic National Park and vicinity and a few samples from other nearby localities. Most of the samples are from the Chaos Crags and Cinder Cone eruptive sequences. Brief summaries are given of the Chaos Crags and Cinder Cone eruptive sequences.

California↗
USGS2008

Major and EDXRF Trace Element Chemical Analyses of Volcanic Rocks from Lassen Volcanic National Park and Vicinity, California

This open-file report presents WDXRF major-element chemical data for late Pliocene to Holocene volcanic rocks collected from Lassen Volcanic National Park and vicinity, California. Data for Rb, Sr, Ba, Y, Zr, Nb, Ni, Cr, Zn and Cu obtained by EDXRF are included for many samples. Data are presented in an EXCEL spreadsheet and are keyed to rock units as displayed on the Geologic Map of Lassen Volcanic National Park and vicinity (Clynne and Muffler, in press). Location of the samples is given in latitude and longitude in degrees and decimal minutes and in decimal degrees.

Open-File Report↗
USGS2008

The Pleistocene eruptive history of Mount St. Helens, Washington, from 300,000 to 12,800 years before present

We report the results of recent geologic mapping and radiometric dating that add considerable detail to our understanding of the eruptive history of Mount St. Helens before its latest, or Spirit Lake, stage. New data and reevaluation of earlier work indicate at least two eruptive periods during the earliest, or Ape Canyon, stage, possibly separated by a long hiatus: one about 300-250 ka and a second about 160–35 ka. Volcanism during this stage included eruption of biotite- and quartz-bearing dacite domes and pyroclastic flows in the area west of and beneath the present-day edifice, accompanied by the deposition of set C tephras. Ape Canyon-stage rocks are compositionally similar to younger Mount St. Helens dacite. The Cougar stage, about 28-18 ka, was probably the most active eruptive stage in Mount St. Helens’ history before the Spirit Lake stage. During the Cougar stage, a debris avalanche buried the area south of the present-day edifice, and voluminous pyroclastic flows, dacite domes, tephra, and a large volume pyroxene andesite lava flow were erupted. Two tephra sets, M and K, were deposited midway through this stage. Swift Creek-stage deposits were emplaced in two phases, beginning about 16 ka and ending about 12.8 ka. During the first phase, set S tephras and three large fans and at least one smaller fan of dacitic fragmental material were deposited on the northwest, west, south, and southeast flanks of Mount St. Helens. The fans are dominated by lithic pyroclastic-flow deposits associated with dome building but include both primary and reworked material from pumiceous pyroclastic flows and lahars. One Swift Creek-age dome on the west flank of the volcano has been located, and others must have been nearby. During the second phase, set J tephras were deposited, but no pyroclastic flows or domes are known to be associated with the andesitic set J tephras. Preliminary petrographic analysis of these older rocks suggests that the volcano’s magmatic system was simpler during the Ape Canyon stage than during subsequent stages and that the magmatic system has evolved from relatively simple to more complex as the volcano matured. Compositional cycles as envisioned by C.A. Hopson and W.G. Melson for the Spirit Lake stage probably did not occur during the Ape Canyon stage but developed later during the Cougar and Swift Creek stages.

Washington↗
USGS2008

Petrology of the 2004-2006 Mount St. Helens lava dome -- implications for magmatic plumbing and eruption triggering

Eighteen years after dome-forming eruptions ended in 1986, and with little warning, Mount St. Helens began to erupt again in October 2004. During the ensuing two years, the volcano extruded more than 80×10 6 m 3 of gas-poor, crystal-rich dacite lava. The 2004-6 dacite is remarkably uniform in bulk-rock composition and, at 65 percent SiO 2 , among the richest in silica and most depleted in incompatible elements of the magmas erupted at Mount St. Helens during the past 500 years. Since shortly after the first spine of lava appeared, samples have been collected using a steel box dredge (“Jaws”) suspended 20-35 m below a helicopter and, occasionally, by hand sampling. As of the spring of 2006, 25 age-controlled samples have been collected from the seven spines of the new lava dome. Samples were obtained from both the interiors of spines and from their carapaces, which are composed of fault gouge and cataclasite 1-2 m thick. The dacite lava is crystal rich, with 40-50 percent phenocrysts. The groundmass is extensively crystallized to a cotectic assemblage of quartz, tridymite, and Na- and K-rich feldspar microlites, raising the total crystal content to more than 80 percent on a vesicle-free basis in all but the earliest erupted samples. Early samples and those collected from near the spine margin are more glassy and vesicular that those collected later and from the interior of the spines. Oxide thermobarometer determinations for the earliest erupted samples we collected cluster at temperatures of approximately 850&deg;C and at an oxygen fugacity one log unit above the nickel-nickel oxide (NNO) buffer curve. In contrast, samples from relatively glass-poor samples erupted in late 2004 and early 2005 have zoned oxides with apparent temperatures that range to greater than 950&deg;C. The higher temperatures in these microlite-rich rocks are attributed to latent heat evolved during extensive and rapid groundmass crystallization. Low volatile contents of matrix glasses and presence of tridymite and quartz in the high-silica rhyolite matrix glass indicate extensive shallow (<1 km) crystallization of the matrix, driven by degassing of water and solidifying the magma below the level of the vent. The mode of eruption of the dacite as a series of fault-gouge-mantled spines is explained by this process of extensive subvent degassing and solidification. Although the dacite from this eruption is more silica rich than 1980-86 dome rocks, most major and trace element concentrations of the 1980-86 and 2004-6 magma batches are similar, and magmatic gas emissions have been low and have had similar ratios to those of the 1980s, raising the possibility that the magma might be residual from the 1980–86 reservoir. However, titanium and chromium are enriched slightly relative to the most recent 1980-86 and Goat Rocks (A.D. 1800-1857) eruptive cycles, and heavy rare-earth-element abundances are slightly depleted relative to those erupted during the past 500 years at Mount St. Helens. These data suggest either addition of new gas-poor dacite magma or tapping of a region of the preexisting reservoir that was not erupted previously. A relatively low pressure of last phenocryst growth suggests that the magma was derived from near the apex of the Mount St. Helens magma reservoir at a depth of about 5 km. Viewed in the context of seismic, deformation, and gas-emission data, the petrologic and geochemical data can be explained by ascent of a geochemically distinct batch of magma into the apex of the reservoir during the period 1987-97, followed by upward movement of magma into a new conduit beginning in late September 2004. The question of new versus residual magma has implications for the long-term eruptive behavior of Mount St. Helens, because arrival of a new batch of dacitic magma from the deep crust could herald the beginning of a new long-term cycle of eruptive activity. It is also important to our understanding of what triggered the eruption and its future course. Two hypotheses for triggering are considered: (1) top-down fracturing related to the shallow groundwater system and (2) an increase in reservoir pressure brought about by recent magmatic replenishment. With respect to the future course of the eruption, similarities between textures and character of eruption of the 2004-6 dome and the long-duration (greater than 100 years) pre-1980 summit dome, along with the low eruptive rate of the current eruption, suggest that the eruption could continue sluggishly or intermittently for years to come.

Washington↗
USGS2008

Plagioclase populations and zoning in dacite of the 2004-2005 Mount St. Helens eruption: Constraints for magma origin and dynamics

We investigated plagioclase phenocrysts in dacite of the 2004-5 eruption of Mount St. Helens to gain insights into the magmatic processes of the current eruption, which is characterized by prolonged, nearly solid-state extrusion, low gas emission, and shallow seismicity. In addition, we investigated plagioclase of 1980-86 dacite. Light and Nomarski microscopy were used to texturally characterize plagioclase crystals. Electron microprobe analyses measured their compositions. We systematically mapped and categorized all plagioclase phenocrysts in a preselected area according to the following criteria: (1) occurrence of zones of acicular orthopyroxene inclusions, (2) presence of dissolution surface(s), and (3) spatial association of 1 and 2. Phenocrysts fall into three main categories; one category contains four subcategories. The range of anorthite (An) content in 2004-5 plagioclase is about An 57-35 during the last 30-40 percent crystallization of plagioclase phenocrysts. Select microphenocrysts (10-50 &mu;m) range from An 30 to An 42 . Anorthite content is lowest near outermost rims of phenocrysts, but zonation patterns between interior and rim indicate variable trends that correlate with textural features. Crystals without dissolution surfaces (about 14 percent of total) show steadily decreasing An content outward to the crystal rim (outer ~80 &mu;m). All other crystals are banded as a consequence of dissolution; dissolution surfaces are band boundaries. Such crystals display normal outward An zoning within a single band that, following dissolution, is then overgrown abruptly by high-An material of the next band. Swarms of acicular orthopyroxene inclusions in plagioclase are characteristic of 2004-5 dacite. They occur mostly inward of dissolution surfaces, where band composition reaches lowest An content. The relative proportions of the three crystal types are distinctly different between 2004-5 dacite and 1980s dome dacite. We propose that crystals with no dissolution surfaces are those that were supplied last to the shallow reservoir, whereas plagioclase with increasingly more complex zoning patterns (that is, the number of zoned bands bounded by dissolution surfaces) result from prolonged residency and evolution in the reservoir. We propose that banding and An zoning across multiple bands are primarily a response to thermally induced fluctuations in crystallinity of the magma in combination with recharge; a lesser role is ascribed to cycling crystals through pressure gradients. Crystals without dissolution surfaces, in contrast, could have grown only in response to steady(?) decompression. Some heating-cooling cycles probably postdate the final eruption in 1986. They resulted from small recharge events that supplied new crystals that then experienced resorption-growth cycles. We suggest that magmatic events shortly prior to the current eruption, recorded in the outermost zones of plagioclase phenocrysts, began with the incorporation of acicular orthopyroxene, followed by last resorption, and concluded with crystallization of euhedral rims. Finally, we propose that 2004-5 dacite is composed mostly of dacite magma that remained after 1986 and underwent subsequent magmatic evolution but, more importantly, contains a component of new dacite from deeper in the magmatic system, which may have triggered the new eruption.

Washington↗
USGS2002

Solubility of NaCl and KCl in aqueous HCl from 20 to 85°C

The solubilities of NaCl and KCl in aqueous HCl solutions were determined from 20 to 85 &deg; C at concentrations ranging from 0 to 20 g of HCl/100 g of solution. Equations are given that describe the solubilities over the range of conditions studied. For NaCl and KCl respectively measured solubilities show an average deviation from these equations of ??0.10 and ??0.08 g/100 g of saturated solution.

Journal of Chemical and Engineering Data↗
USGS2002

Osmium isotope constraints on lower crustal recycling and pluton preservation at Lassen Volcanic Center, CA

Osmium isotope compositions of intermediate- to silicic-composition calc-alkaline volcanic rocks from the Lassen volcanic region of the Cascade arc are significantly more radiogenic ( γ Os =+23 to +224) than typical mantle. These evolved arc rocks in the Lassen region have unradiogenic Sr, Nd, and Pb isotope compositions which overlap with those of contemporaneous mafic lavas. Crystal fractionation of mafic- to intermediate-composition magmas produces Re/Os ratios that are high enough to evolve to very radiogenic Os isotope compositions in only a few million years, providing a potential fingerprint for detecting the involvement of such young, relatively mafic crust in magmatic systems. However, the Sr, Nd, and Pb isotope compositions will remain constant over such short time intervals due to relatively low parent/daughter enrichment during magmatic evolution. The radiogenic Os isotope compositions in typically evolved Lassen rocks are interpreted to reflect significant interaction with lower crustal material that has radiogenic Os isotope compositions. Beneath this section of the Cascade arc, large amounts of such high- γ Os lower crust may have formed and been isolated from MASH zone mixing and homogenization processes during the Pliocene or Late Miocene. The results from this study indicate that Os isotopes may provide a unique glimpse into lower crustal processes, such as recycling, in primitive orogenic arcs.

California↗
USGS2002

Geologic map of the Lassen Peak, Chaos Crags, and Upper Hat Creek area, California

This digital publication contains all the information used to publish U.S. Geological Survey Geologic Investigations Series I-2723 (Christiansen and others, 2002). The map shows the distribution and relationships of volcanic and surficial-sedimentary deposits in an area of Lassen Volcanic National Park and vicinity. Emphasis is on products of the 1914-1917 eruptions of Lassen Peak and the approximately 1000-year-old eruptions of Chaos Crags. ArcInfo grids were prepared from scanned composite images of four U.S. Geological Survey 7.5' topographic quadrangle maps and were georeferenced and reprojected.

IMAP↗
USGS2000

Revised age of the Rockland tephra, northern California: Implications for climate and stratigraphic reconstructions in the western United States: Reply

Sarna-Wojcicki suggests that the 40 Ar/ 39 Ar age of 614 ± 8 ka for the Rockland tephra ( Lanphere et al., 1999 ) is too old because of the presence of xenocrystic plagioclase. The Rockland tephra is indeed full of lithic debris that can be seen at any well-exposed outcrop of ash-flow or air-fall deposits. In order to minimize contamination, we selected pumice lumps known to be representative of the Rockland magma. Plagioclase in the pumice lumps forms a homogeneous population of weakly zoned phenocrysts. By contrast, plagioclase from the intermediate to silicic volcanic lithic fragments in the Rockland tephra typically displays complex zoning, variable resorption patterns and strong discontinuities. Such plagioclase would be readily recognizable if present in the Rockland magma. We saw no petrographic evidence that the Rockland magma was contaminated with xenocrystic plagioclase. The pumice lumps were carefully cleaned before mineral separations were made.

California↗
USGS1999

Eruptions of Lassen Peak, California, 1914 to 1917

On May 22, 1915, an explosive eruption at Lassen Peak, California, the southernmost active volcano in the Cascade Range, devastated nearby areas and rained volcanic ash as far away as 200 miles to the east. This explosion was the most powerful in a 1914&ndash;17 series of eruptions that were the last to occur in the Cascades before the 1980 eruption of Mount St. Helens, Washington. Recent work by scientists with the U.S. Geological Survey (USGS) in cooperation with the National Park Service is shedding new light on these eruptions.

California↗
USGS1996

Geology and geothermal potential of Alid volcanic center, Eritrea, Africa

Alid volcanic center, a 700-meter-tall mountain in Eritrea, northeast Africa, straddles the axis of an active crustal-spreading center called the Danakil Depression. Boiling-temperature fumaroles are common on Alid, and their gas compositions indicate a reservoir temperature of at least 250 ??C. The history of volcanism and the high reservoir temperature indicated by the Alid fumarole gases suggest that a geothermal resource of electrical grade lies beneath the mountain. Though drilling is needed to determine subsurface conditions, the process of dome formation and the ongoing crustal spreading can create and maintain fracture permeability in the hydrothermal system that feeds the Alid fumaroles.

Conference Paper↗
USGS1978

Solubility of highly soluble salts in aqueous media - Part 1, NaCl, KCl, CaCl 2 , Na 2 SO 4 , and K 2 SO 4 solubilities to 100°C

A modified visual method for determining the solubility of highly soluble salts in aqueous media up to 100&deg; C is presented. The solubilities of NaCl, KCl, CaCl 2 , Na 2 SO 4 , and K 2 SO 4 were determined up to 100&deg; C. The tabulated experimental data and the fitted equations describing the data indicate that the previous literature data for the solubility of these salts were generally high by 0.05 to 2.0 weight percent salt.

Journal of Research of the U.S. Geological Survey↗