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D. R. Sherrod

Publications and source records attributed to D. R. Sherrod.

At least 19 recordsLinked to original sources
USGS2008

Digital data for volcano hazards at Newberry Volcano, Oregon

Newberry volcano is a broad shield volcano located in central Oregon, the product of thousands of eruptions, beginning about 600,000 years ago. At least 25 vents on the flanks and summit have been active during the past 10,000 years. The most recent eruption 1,300 years ago produced the Big Obsidian Flow. Thus, the volcano's long history and recent activity indicate that Newberry will erupt in the future. Newberry Crater, a volcanic depression or caldera has been the focus of Newberry's volcanic activity for at least the past 10,000 years. Newberry National Volcanic Monument, which is managed by the U.S. Forest Service, includes the caldera and extends to the Deschutes River. Newberry volcano is quiet. Local earthquake activity (seismicity) has been trifling throughout historic time. Subterranean heat is still present, as indicated by hot springs in the caldera and high temperatures encountered during exploratory drilling for geothermal energy. The report USGS Open-File Report 97-513 (Sherrod and others, 1997) describes the kinds of hazardous geologic events that might occur in the future at Newberry volcano. A hazard-zonation map is included to show the areas that will most likely be affected by renewed eruptions. When Newberry volcano becomes restless, the eruptive scenarios described herein can inform planners, emergency response personnel, and citizens about the kinds and sizes of events to expect. The geographic information system (GIS) volcano hazard data layers used to produce the Newberry volcano hazard map in USGS Open-File Report 97-513 are included in this data set. Scientists at the USGS Cascades Volcano Observatory created a GIS data layer to depict zones subject to the effects of an explosive pyroclastic eruption (tephra fallout, pyroclastic flows, and ballistics), lava flows, volcanic gasses, and lahars/floods in Paulina Creek. A separate GIS data layer depicts drill holes on the flanks of Newberry Volcano that were used to estimate the probability of coverage by future lava flows.

Open-File Report↗
USGS2006

Youngest volcanism about 1 million years ago at Kahoolawe Island, Hawaii

Young volcanic deposits in Kahoolawe Island, cutting up through the caldera-filling lava, colluvium and talus in the west wall of Kanapou Bay, had long been stratigraphically considered the rejuvenated-stage products. New K-Ar ages, combined with magnetic polarity data, show that young volcanism was at about 0.98-1.04 Ma and indicate no substantial quiescence between the filling of the caldera and the young volcanism. This result, and the tholeiitic characteristics of the young deposits, suggest they are a component of late shield-stage volcanism. ?? 2005 Elsevier B.V. All rights reserved.

Hawaii↗
USGS2003

Kilauea east rift zone magmatism: An episode 54 perspective

On January 29 30, 1997, prolonged steady-state effusion of lava from Pu'u'O'o was briefly disrupted by shallow extension beneath Napau Crater, 1 4 km uprift of the active Kilauea vent. A 23-h-long eruption ( episode 54 ) ensued from fissures that were overlapping or en echelon with eruptive fissures formed during episode 1 in 1983 and those of earlier rift zone eruptions in 1963 and 1968. Combined geophysical and petrologic data for the 1994 1999 eruptive interval, including episode 54 , reveal a variety of shallow magmatic conditions that persist in association with prolonged rift zone eruption. Near-vent lava samples document a significant range in composition, temperature and crystallinity of pre-eruptive magma. As supported by phenocryst liquid relations and Kilauea mineral thermometers established herein, the rift zone extension that led to episode 54 resulted in mixture of near-cotectic magma with discrete magma bodies cooled to ≤1100°C. Mixing models indicate that magmas isolated beneath Napau Crater since 1963 and 1968 constituted 32 65% of the hybrid mixtures erupted during episode 54 . Geophysical measurements support passive displacement of open-system magma along the active east rift conduit into closed-system rift -reservoirs along a shallow zone of extension. Geophysical and petrologic data for early episode 55 document the gradual flushing of episode 54 related magma during magmatic recharge of the edifice.

Hawaii↗
USGS1997

Diverse primitive magmas in the Cascade arc, Northern Oregon and Southern Washington

Bulk-rock major- and trace-element composition, petrography and mineral compositions are presented for a diverse suite of 22 primitive mafic lavas in the Cascade Range of northern Oregon and southern Washington. With the exception of an early Western Cascade basalt, all the rocks are younger than 7 Ma. Intensive parameters [F(H2O), f(O2), T, P] for the magmas have been inferred mostly from equilibrium olivine-liquid and plagioclase-liquid relations. Nearly anhydrous, MORB-like, low-K tholeiite was probably derived from relatively high degrees of decompression-induced melting of shallow, depleted, relatively unmetasomatized lithospheric mantle during intra-arc rifting. The degree of partial melting decreases northward along the arc, whereas the depth of average melt generation increases. OIB-like basalt represents deeper, wetter, smaller-degree melts of more enriched asthenospheric mantle, unaffected by subduction. Olivine analcimite resembles the silicate melt considered responsible for within-plate mantle metasomatism. Post-7-Ma subduction-related basalt was derived by low degrees of partial melting of subduction-metasomatized garnet lherzolite, similar to OIB-like basalt source-mantle before modification. The spectrum of subduction-related basalt from cooler and wetter (and slightly more oxidized) absarokite to progressively hotter and drier high-K calc-alkaline basalt and calc-alkaline basalt seems to be due to varying degrees of metasomatism of the deep mantle wedge by relatively cool, wet, LILE-rich absarokitic magmas coming from near the subducted slab. Early Western Cascade basalt is more typically arc-like in its composition and mineralogy, and was probably generated under H2O-rich conditions when more vigorous subduction prevailed. Depleted basaltic andesite may have been generated by low degrees of partial melting of residual harzburgite, possibly formed during the generation of early Western Cascade basalt.

Canadian Mineralogist↗
USGS1995

Geologic map of Newberry Volcano, Deschutes, Klamath, and Lake counties, Oregon

Newberry volcano, one of the largest Quaternary volcanoes in the conterminous United States, is a broad shieldlike landform with a summit caldera 7 km across. It comprises the products of thousands of eruptions, at least 25 of which occurred during the last 10,000 years (Holocene Epoch). Eruptions have occurred as recently as 1,300 years ago, but isotopic ages indicate that the volcano began its growth as early as 0.6 million years ago. Thus, its long history and recent activity indicate that Newberry volcano is likely to erupt in the future.

Oregon↗
USGS1993

Heat flow from four new research drill holes in the Western Cascades, Oregon, U.S.A.

Conceptual models of the thermal structure of the Oregon Cascade Range propose either (1) a narrow zone of magmatic heat sources, flanked by shallow heat-flow anomalies caused by lateral ground-water flow; or (2) a wide zone of magmatic heat sources, with localized, generally negligible ground-water effects. The proposed narrow heat source coincides with the Quaternary volcanic arc, whereas the wider heat source would extend 10–30 km west of the arc. To test the models, four new heat-flow holes were sited west of the Quaternary arc but within the area of the proposed wide heat source. The sites are separated from the Quaternary arc by topographic divides and (or) major river valleys, so that heating by regional-scale ground-water flow seems unlikely. Measured heat flow (76±5 mW mm −2 ) was significantly lower than the values predicted by interpolation from an existing heat-flow contour map (95±7 mW m −2 ). The lower values are consistent with a narrow zone of magmatic heat sources. The complete heat-flow data set consists mostly of shallow (100–200 m) data and defines lobate highs around hot-spring groups in the Western Cascades. However, all of the deepest holes in the study area (44°–45°15′N) show hydrologic gradient disturbances extending to depths >200 m, so the shallow data must be extrapolated with caution.

Oregon↗
USGS1993

Historic and prehistoric earthquakes near Klamath Falls, Oregon

Earthquakes have rocked the Klamath Falls in the past will continue to do so in the future. Scientists estimate the likelihood of future damaging earthquakes in an area by examining the area's past record of earthquakes and by evaluating the area's earthquake potential in relationship to its geologic setting. To supplement the historic catalog, which often covers only a short time span, they also attempt to identify prehistoric earthquakes preserved in the rocks and sediments of the area. The conclusion drawn from such studies in the Klamath Falls area is that earthquakes in the 4-6 magnitude range, which are capable of light to moderate damage, occur on the order of one or more every few decades. Even a major earthquake in the 7+ magnitude range cannot be ruled out at some future time. However, the area's historic record, which goes back only about 100 yrs, is too short to estimate the frequency of such large shocks. This article is a brief summary of the geologic setting and the historic and prehistoric record of earthquakes in Klamath Falls and the surrounding area.

Oregon↗
USGS1990

Geothermal segmentation of the Cascade Range in the USA

Characteristics of the crustal thermal regime of the Quaternary Cascades vary systematically along the range. Spatially congruent changes in volcanic vent distribution, volcanic extrusion rate, hydrothermal discharge rate, and regional conductive heat flow define 5 geothermal segments. These segments are, from north to south: (1) the Washington Cascades north of Mount Rainier, (2) the Cascades from Mount Rainier to Mount Hood, (3) the Oregon Cascades from south of Mount Hood to the California border, (4) northernmost California, including Mount Shasta and Medicine Lake volcano, and (5) the Lassen region of northern California. This segmentation indicates that geothermal resource potential is not uniform in the Cascade Range. Potential varies from high in parts of Oregon to low in Washington north of Mount Rainier.

Conference Paper↗
USGS1989

Heat flow and hydrothermal circulation in the Cascade Range, north-central Oregon

In north-central Oregon a large area of near-zero near-surface conductive heat flow occurs in young volcanic rocks of the Cascade Range. Recent advective heat flux measurements and a heat-budget analysis suggest that ground-water circulation sweeps sufficient heat out of areas where rocks younger than 6 Ma (million years ago) are exposed to account for the anomalously high advective and conductive heat discharge measured in older rocks at lower elevations. Earlier workers have proposed that an extensive midcrustal magmatic heat source is responsible for this anomalously high heat flow. Instead, high heat flow in the older rocks may be a relatively shallow phenomenon caused by regional ground-water flow. Any deeper anomaly may be relatively narrow, spatially variable, and essentially confined to the Quaternary (less than 2 Ma) arc. Magmatic intrusion at a rate of 9 to 33 cubic kilometers per kilometer of arc length per million years can account for the total heat flow anomaly. Deep drilling in the areas of high heat flow in the older rocks could indicate which model is more appropriate for the near-surface heat flow data.

Oregon↗