scholarly journals A Multidisciplinary Investigation Into the Eruptive Style, Processes, and Duration of a Cascades Back-Arc Tholeiitic Basalt: A Case Study of the Brushy Butte Flow Field, Northern California, United States

2021 ◽  
Vol 9 ◽  
Author(s):  
Drew T. Downs ◽  
Duane E. Champion ◽  
Michael A. Clynne ◽  
L. J. Patrick Muffler
Keyword(s):  
United States ◽  
Flow Field ◽  
Tholeiitic Basalt ◽  
Time Interval ◽  
Northern California ◽  
Cosmogenic Dating ◽  
Eruptive History ◽  
Element Abundances ◽  
Multidisciplinary Study ◽  
Back Arc

The Cascades back-arc in northern California is dominated by monogenetic tholeiitic basalts that erupted throughout the Pleistocene. Elucidating their eruptive history and processes is important for understanding potential future eruptions here. We focus on the well-exposed monogenetic volcano that emplaced the Brushy Butte flow field, which constructed a ∼150 m tall edifice, has flow lobes up to >10 km long, and in total covers ∼150 km2 with an eruptive volume of 3.5 km3. We use a multidisciplinary approach of field mapping, petrography, geochemistry, paleomagnetism, geochronology, and lidar imagery to unravel the eruptive history and processes that emplaced this flow field. Tholeiitic basalts in northern California have diverse surface morphology and vegetation cover but similar petrographic appearances, which makes them hard to distinguish in the field. Geochemistry and paleomagnetism offer an independent means of distinguishing tholeiitic basalts. Brushy Butte flow field lavas are similar in major-oxide and trace-element abundances but differ from adjacent tholeiitic basalts. This is also apparent in remanent magnetic directions. Additionally, paleomagnetism indicates that the flow field was emplaced during a geologically brief time interval (10–20 years), which 36Cl cosmogenic dating puts at 35.7 ± 1.7 ka. Lidar imagery shows that these flows erupted from at least 28 vents encompassing multiple scoria cones, spatter cones, and craters. Flows can be grouped into four pulses using stratigraphic position and volume. Pulse 1 is the most voluminous, comprising eight eruptions and ∼2.3 km3. Each subsequent pulse started rapidly but decayed quickly, and each successive pulse erupted less lava (i.e., 2.3 km3 for pulse 1, 0.6 km3 for pulse 2, 0.3 km3 for pulse 3, and 0.2 km3 for pulse 4). Many of these flows host well-established lava channels and levees (with channel breakouts) that lead to lava fans, with some flows hosting lava ponds. Similar flow features from tholeiitic eruptions elsewhere demonstrate that these morphologies generally occur over weeks, months, or longer (e.g., Puʻu ʻŌʻō eruption at K–llauea, Hawaiʻi). This multidisciplinary study shows the range of eruptive styles and durations of a Cascades back-arc eruption and illustrates how potential future tholeiitic eruptive activity in the western United States might progress.

The connection between the «color revolutions» and the strategic doctrines of the United States (late 20th century — 2014)

2021 ◽  
Author(s):  
Anna Igorevna Filimonova
Keyword(s):  
United States ◽  
20Th Century ◽  
American Foreign Policy ◽  
Use Of Force ◽  
The United States ◽  
Time Interval ◽  
Late 20Th Century ◽  
The Us ◽  
Color Revolutions ◽  
The Right

After the collapse of the USSR, fundamentally new phenomena appeared on the world arena, which became a watershed separating the bipolar order from the monopolar order associated with the establishment of the US global hegemony. Such phenomena were the events that are most often called «revolutions» in connection with the scale of the changes being made — «velvet revolutions» in the former Eastern Bloc, as well as revolutions of a different type, which ended in a change in the current regimes with such serious consequences that we are also talking about revolutionary transformations. These are technologies of «color revolutions» that allow organizing artificial and seemingly spontaneous mass protests leading to the removal of the legitimate government operating in the country and, in fact, to the seizure of power by a pro-American forces that ensure the Westernization of the country and the implementation of "neoliberal modernization", which essentially means the opening of national markets and the provision of natural resources for the undivided use of the Western factor (TNC and TNB). «Color revolutions» are inseparable from the strategic documents of the United States, in which, from the end of the 20th century, even before the collapse of the USSR, two main tendencies were clearly traced: the expansion of the right to unilateral use of force up to a preemptive strike, which is inextricably linked with the ideological justification of «missionary» American foreign policy, and the right to «assess» the internal state of affairs in countries and change it to a «democratic format», that is, «democratization». «Color revolutions», although they are not directly mentioned in strategic documents, but, being a «technical package of actions», straightforwardly follow from the right, assigned to itself by Washington, to unilateral use of force, which is gradually expanding from exclusively military actions to a comprehensive impact on an opponent country, i.e. essentially a hybrid war. Thus, the «color revolutions» clearly fit into the strategic concept of Washington on the use of force across the entire spectrum (conventional and unconventional war) under the pretext of «democratization». The article examines the period of registration and expansion of the US right to use force (which, according to the current international law, is a crime without a statute of limitations) in the time interval from the end of the twentieth century until 2014, filling semantic content about the need for «democratic transformations» of other states, with which the United States approached the key point of the events of the «Arab spring» and «color revolutions» in the post-Soviet space, the last and most ambitious of which was the «Euromaidan» in Ukraine in 2014. The article presents the material for the preparation of lectures and seminars in the framework of the training fields «International Relations» and «Political Science».

Plume-modified mantle flow in the northern Basin and Range and southern Cascadia back-arc region since ca. 12 Ma

Geology ◽  
2019 ◽  
Vol 47 (8) ◽  
pp. 695-699 ◽  
Author(s):  
Victor E. Camp
Keyword(s):  
United States ◽  
Seismic Velocity ◽  
Flow Line ◽  
Basin And Range ◽  
Mantle Flow ◽  
Low Density ◽  
Low Velocity ◽  
Northern Basin ◽  
High Lava Plains ◽  
Back Arc

AbstractBimodal volcanism and rhyolite migration along the High Lava Plains in central Oregon (United States) lie above a broader feature defined by low seismic velocity in the upper mantle that emanates from the Yellowstone hotspot (northwest United States) and extends westward across the northern Basin and Range. It was emplaced by a westward current, driven in part by rapid buoyancy-driven flow across the east-west cratonic boundary of North America. Geothermometry studies and geochemical considerations suggest that the low-velocity feature may be composed of moderately hot, low-density mantle derived from the Yellowstone plume but diluted by thermomechanical erosion and entrainment of colder mantle lithosphere. Finger-like conduits of plume-modified mantle beneath Quaternary eruption sites delineate flow-line channels that have developed across the broader mantle structure since 2 Ma. These channels have allowed low-density mantle to accumulate against the Cascades arc, thus providing a heated mantle source for mafic magmatism in the Newberry (Oregon) and Medicine Lake (California) volcanic fields.

Impediments to prescribed fire across agency, landscape and manager: an example from northern California

2012 ◽  
Vol 21 (3) ◽  
pp. 210 ◽  
Author(s):  
Lenya N. Quinn-Davidson ◽  
J. Morgan Varner
Keyword(s):  
United States ◽  
Prescribed Fire ◽  
Prescribed Burning ◽  
Social Constraints ◽  
Northern California ◽  
Eastern United States ◽  
Environmental Laws ◽  
The Public ◽  
Management Objectives ◽  
Fire Activity

Though the need for prescribed fire is widely recognised, its use remains subject to a range of operational and social constraints. Research has focussed on identifying these constraints, yet past efforts have focussed disproportionately on single agencies and geographic regions. We examined constraints on prescribed fire by surveying a wide variety of organisations (including six state and federal agencies and several tribes, non-governmental organisations and timber companies) in northern California, a fire-prone region of the western United States. Across the region, prescribed burning annually covered only 38% of the area needed to fulfil land-management objectives, and 66% of managers indicated dissatisfaction with levels of prescribed fire activity. The highest-ranked impediments were narrow burn window, regulations, lack of adequate personnel and environmental laws. Impediment ratings differed among entities, with legal and social impediments of greater concern in the private sector than in the public, and economic impediments of greater concern in the state and private sectors than in the federal. Comparisons with the south-eastern United States, where similar research has taken place, point to important regional constraints on prescribed fire activity. These findings suggest further need for research spanning geographic and ownership boundaries, as prescribed fire impediments can vary by context.

Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1216-1220
Author(s):  
Drew T. Downs ◽  
Duane E. Champion ◽  
Patrick Muffler ◽  
Robert L. Christiansen ◽  
Michael A. Clynne ◽  
...  
Keyword(s):  
Magma Ascent ◽  
Middle Pleistocene ◽  
Normal Faults ◽  
Northern California ◽  
Spatially Distributed ◽  
Dry Lake ◽  
Eruption Age ◽  
Tectonic Settings ◽  
Back Arc ◽  
Crustal Magma

Abstract Mapping and chronology are central to understanding spatiotemporal volcanic trends in diverse tectonic settings. The Cascades back arc in northern California (USA) hosts abundant lava flows and normal faults, but tholeiitic basalts older than 200 ka are difficult to discriminate by classic mapping methods. Paleomagnetism and chemistry offer independent means of correlating basalts, including the Tennant, Dry Lake, and Hammond Crossing basalt fields. Paleomagnetic analysis of these chemically similar basalts yield notable overlap, with statistical analysis yielding 7 chances in 1,000,000 that their similar mean remanent directions are random. These basalts also have overlapping 40Ar/39Ar ages of 272.5 ± 30.6 ka (Tennant), 305.8 ± 23.9 ka (Dry Lake), and 300.4 ± 15.2 and 322.6 ± 17.4 ka (Hammond Crossing). Chemical and paleomagnetic analyses indicate that these spatially distributed basalts represent simultaneous (<100 yr uncertainty) eruptions, and thus we use 305.5 ± 9.8 ka (weighted mean) as the eruption age. Their vents align on a N25°W trend over a distance of 39 km. Tennant erupted the largest volume (3.55 ± 0.75 km3) at the highest elevation; both factors decay to the south-southeast at Dry Lake (0.75 ± 0.15 km3) and Hammond Crossing (0.15 ± 0.05 km3). We propose vertical magma ascent beneath the Tennant vent area, where the most evolved, high-SiO2 magma erupted, with lateral dike propagation in the brittle crust. Propagation was near orthogonal to east-west extension (0.3–0.6 mm/yr) along north-northwest–trending normal faults.

Analysis of Inpatient and Emergency Department Serial Troponin Testing Intervals in the United States

2020 ◽  
Author(s):  
Andrew Fletcher ◽  
Erik Forsman ◽  
Brian R Jackson
Keyword(s):  
United States ◽  
Emergency Department ◽  
Median Time ◽  
Emergency Departments ◽  
The United States ◽  
Published Data ◽  
Time Interval ◽  
Time Intervals ◽  
Convenience Sample ◽  
Facility Level

Abstract Background Serial measurement of cardiac troponins (cTn) is central to the diagnosis of myocardial infarction. The time intervals between individual measurements may impact the speed and reliability of diagnosis. Published recommendations exist for these time intervals, but there is little previously published data on actual intervals in routine clinical settings. Methods Retrospective analysis of cTn testing intervals was performed from a convenience sample of 37 hospitals. All 37 provided data on inpatient tests and 19 also provided separate data for tests ordered in their emergency departments. Facilities included both academic and community hospitals across the United States. For each facility, the median time interval between serial cTn order collections was determined separately for inpatient orders and emergency department orders. Results The facility-level median time intervals between serial inpatient cTn test orders ranged from 3.17 to 7.32 hours. Facility-level median time intervals between serial emergency department cTn orders ranged from 1.48 to 4.23 hours. There was no observed difference between academic and nonacademic facilities. Conclusion Typical time intervals between serial cTn orders varied widely across hospitals, and in many cases reflected suboptimal care. Time intervals were generally shorter for cTn testing ordered in emergency departments. Existing testing protocols should be re-examined.

A new species of stonecrop (Sedum section Gormania, Crassulaceae) from northern California

Phytotaxa ◽  
2014 ◽  
Vol 159 (2) ◽  
pp. 111
Author(s):  
Peter Zika
Keyword(s):  
United States ◽  
New Species ◽  
The United States ◽  
Northern California ◽  
Klamath Mountains ◽  
Narrow Endemic ◽  
Deep Yellow ◽  
A New Species

Sedum citrinum is described as a narrow endemic from three populations on ultramafic bedrock in the Klamath Mountains of southern Del Norte County, California, in the United States. It is distinguished from Sedum obtusatum subsp. boreale by its flattened inflorescence with elongate lower branches, as well as its deep yellow flowers and yellow anthers. 

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

Geology ◽  
1999 ◽  
Vol 27 (2) ◽  
pp. 135 ◽  
Author(s):  
Marvin A. Lanphere ◽  
Duane E. Champion ◽  
Michael A. Clynne ◽  
L. J. Patrick Muffler
Keyword(s):  
United States ◽  
Western United States ◽  
Northern California

A 12,000 Kyr Paleohydroclimate Record in the Southeastern, U.S.A based on Deuterium from Bat Guano

2021 ◽  
Author(s):  
Alexandra Tsalickis ◽  
Matthew Neal Waters ◽  
Joshua William Campbell
Keyword(s):  
United States ◽  
Human Impacts ◽  
Southeastern United States ◽  
Sediment Cores ◽  
Population Increase ◽  
Time Interval ◽  
Moisture Regimes ◽  
Climate Proxies ◽  
Bat Guano

Abstract The southeastern United States endures environmental change from human population increase, climate change, and land use alterations creating the need to understand baseline conditions and environmental patterns prior to human impacts. While paleoenvironmental data can be reconstructed from a variety of archives (e.g. lake sediments, tree rings, speleothems), some geographic areas contain fewer of such records. One archive capable of recording moisture regimes and other paleoenvironmental changes over millennia but has received little attention relative to other climate proxies, are bat guano deposits in cave systems. Bat guano deposits are found in many cave environments in the southeastern United States and can be used as an archive of paleoenvironmental data including precipitation, vegetation, and aspects associated with the ecology of bats. Here, we present a 12,000-year record of paleoenvironmental change based on δ2H stable isotopes in a guano core collected from Cave Springs Cave in Alabama, USA. Results suggest distinct shifts in moisture during the lower Holocene/upper Pleistocene (9,551 – 12,131 cal yr BP) (δ2H values -86.82 – -77.70) and during the middle Holocene (3,886 – 9,351 cal yr BP) (δ2H values -125.74 – -80.63), roughly coinciding with the Holocene Climatic Optimum (HCO) time interval (5,000 – 9,000 cal yr BP). During the last 4,000 years, conditions in the region shifted once again in the southeastern United States region. Climate inferences based on guano δ2H are consistent with the role of atmospheric moisture on regional vegetation changes suggested by previous pollen records obtained from lake sediment cores. This study suggests bat guano δ2H may be a reliable method to provide a long-term paleoclimate record.

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