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USGS2011

International heat flow commission celebrates 40 years

The outflow of heat from the Earth's interior is, in terms of energy, the most impressive terrestrial phenomenon. Its present rate of about 1021 joules per year is order‐of‐magnitudes greater than the energy dissipation of earthquakes or heat loss from volcanic eruptions. The study of the Earth's internal heat plays an important role in understanding the Earth's origin, internal constitution, and plate tectonics. The thermal structure of the Earth, generally referred to as the geothermics, or also as the (terrestrial) heat flow, has been studied for a long time. However, modern geothermics, one of the fundamental geophysical disciplines, is relatively young. The International Heat Flow Commission (IHFC), under which the academic geothermal research on the international scale is organized, was created only in 1963. The IHFC, operating under the International Association of Seismology and Physics of the Earth's Interior (IASPEI), covers a broad scope of geophysical studies, and links the activities of other associations of the International Union of Geodesy and Geophysics (IUGG).

Eos, Earth and Space Science News↗

USGS2011

Interdisciplinary discussion of volcanic processes beneath the Long Valley Caldera-Mono Craters Area

Volcanism in the Long Valley Caldera-Mono Craters (LVCMC) volcanic field in eastern California over the past 4 Ma is dominated by the 0.76 Ma caldera-forming eruption of 600 km 3 of rhyolite to form the Bishop Tuff. Over the last 150 k.y., volcanism has concentrated along the Mono-Inyo chain, which extends 45 km north from Mammoth Mountain to Mono Lake (Figure 1, below). Recent eruptions along this chain have occurred from multiple vents 650±50 yr B.P. and from a vent in the middle of Mono Lake ∼300 yr B.P. An earthquake swarm in May 1980, including four M6 earthquakes accompanied by uplift of the resurgent dome in the center of the caldera, called attention to the restless nature of Long Valley caldera. Subsequent activity has included recurring swarms of earthquakes (M≤5.8), episodic uplift of the resurgent dome, diffuse outgassing of magmatic CO 2 , and mid-crustal (10- to 25- km deep), long period (LP) volcanic earthquakes.

California↗

USGS2011

Proposed initiative would study Earth's weathering engine

At the Earth's surface, a complex suite of chemical, biological, and physical processes combines to create the engine that transforms bedrock into soil (Figure 1). Earth's weathering engine provides nutrients to nourish ecosystems and human society mediates the transport of toxic components within the biosphere, creates water flow paths that carve and weaken bedrock, and contributes to the evolution of landscapes at all temporal and spatial scales. At the longest time scales, the weathering engine sequesters CO 2 , thereby influencing long-term climate change. Despite the importance of soil, our knowledge of the rate of soil formation is limited because the weathering zone forms a complex, ever-changing interface, and because scientific approaches and funding paradigms have not promoted integrated research agendas to investigate such complex interactions. No national initiative has promoted a systems approach to investigation of weathering science across the broad array of geology, soil science, ecology and hydrology. Such a program is certainly needed, and this article describes a platform on which to build the initiative to answer the following question: How does the Earth weathering engine break down rock to nourish ecosystems, carve terrestrial landscapes, and control carbon dioxide in the global atmosphere?

Eos Science News↗

USGS2011

Drilling the central crater of the Chesapeake Bay Impact Structure: A first look

The late Eocene Chesapeake Bay impact structure is a well‐preserved example of one of Earth's largest impact craters, and its continental‐shelf setting and relatively shallow burial make it an excellent target for study. Since the discovery of the structure over a decade ago [ Edwards et al., 2004; Poag et al., 2004], test drilling by U.S. federal and state agencies has been limited to the structure's annular trough (Figure 1). In May 2004, the U.S. Geological Survey (USGS) drilled the first scientific test hole into the central crater of the Chesapeake Bay impact structure in Cape Charies,Virginia (Figure 1). This partially cored test hole, the deepest to date, penetrated postimpact sediments and impact breccias to a total depth of 823 m.

Chesapeake Bay↗

USGS2011

Water year 2004: Western water managers feel the heat

This spring, a rare combination of exceptionally warm temperatures and near-record lack of precipitation in the western United States caused a rapid change in hydrologic conditions and an unexpectedly early onset of spring conditions. With much of the western U.S. already in its fifth year of drought, an above-average western snowpack on 1 March 2004 provided hope for much-needed abundant runoff. Unfortunately snowmelt began far earlier than anticipated, resulting in dramatic declines in seasonal spring-summer streamflow forecasts as the month proceeded, declines more rapid by some measures than ever before in the past 75 years. With reservoirs near historic lows, many water users have been hard pressed to deal with the continuing drought.

Eos, Earth and Space Science News↗

USGS2011

Heat wave brings an unprecedented red tide to San Francisco Bay

An exceptional red tide in San Francisco Bay was observed on 8 September 2004. The red tide had chlorophyll concentrations approaching 200 mg/m 3 (Figure 1) in red/purple surface streaks containing high abundances of the dinoflagellate Akashiwo sanguinea. Red tides and harmful algal blooms (HABs) are common features of coastal ecosystems, and their growing frequency is a suspected outcome of coastal eutrophication. However, the authors have never observed a dinoflagellate bloom of this scale during 28 years of sampling in the nutrient-rich San Francisco Bay. Phytoplankton biomass along this transect is typically <5mg Chla/m 3 , and has never exceeded 21 mg Chla/m 3 during summer-autumn.

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USGS2011

Three‐dimensional model for the crust and upper mantle in the Barents Sea region

The Barents Sea and its surroundings is an epicontinental region which previously has been difficult to access, partly because of its remote Arctic location (Figure 1) and partly because the region has been politically sensitive. Now, however, this region, and in particular its western parts, has been very well surveyed with a variety of geophysical studies, motivated in part by exploration for hydrocarbon resources. Since this region is interesting geophysically as well as for seismic verification, a major study [ Bungum et al ., 2004] was initiated in 2003 to develop a three‐dimensional (3‐D) seismic velocity model for the crust and upper mantle, using a grid density of 50 km. This study, in cooperation between NORSAR, the University of Oslo (UiO),and the U.S.Geological Survey (USGS), has led to the construction of a higher‐resolution, regional lithospheric model based on a comprehensive compilation of available seismological and geophysical data. Following the methodology employed in making the global crustal model CRUST5.1 [ Mooney et al ., 1998], the new model consists of five crustal layers: soft and hard sediments, and crystalline upper, middle, and lower crust. Both P ‐ and S ‐wave velocities and densities are specified in each layer. In addition, the density and seismic velocity structure of the uppermost mantle, essential for Pn and Sn travel time modeling, are included.

Eos, Earth and Space Science News↗

USGS2011

River chemistry as a monitor of Yosemite Park mountain hydroclimates

High-frequency, high-altitude measurements of water chemistry provide insights into processes relating to the hydrology, climate, and geochemistry of mountain catchments. When such observations are combined with stream stage, temperature, snow, weather, and other surface hydroclimate measurements, they are particularly useful in allowing connections between climate, river discharge, river chemistry, and ecosystems to be discerned. Climate is the major source of variability in U.S. and global water resources. For example, large-scale variations in the global atmosphere and the Pacific Ocean are responsible for much of the variability in river discharge in Hawaii, Alaska, the U.S. Pacific Northwest, and the U.S. Southwest [ Cayan and Peterson , 1989], and thus are closely linked to water and energy resources of the western United States [ Cayan et al ., 2003].

Eos, Earth and Space Science News↗

USGS2011

Comment on “Comparison between probabilistic seismic hazard analysis and flood frequency analysis”

Despite providing an exceptionally clear example of the basics of probabilistic seismic hazard analysis (PSHA), Wang and Ormsbee [2005] nevertheless conclude that “…using PSHA for risk analysis is not only confusing, but is also inappropriate.” I argue here that (1) the results of a PSHA analysis are not confusing and have physical meaning, and (2) the authors' basis for declaring PSHA “inappropriate” is misguided. I note in passing that the authors consistently confuse “risk” with “hazard.” Both PSHA and flood frequency analysis provide estimates of hazard. Risk is the product of hazard, vulnerability and exposure. This discussion is only concerned with hazard.

Eos Science News↗

USGS2011

Satellite imagery maps Hurricane Katrina-induced flooding and oil slicks

In the early morning of 29 August 2005, Hurricane Katrina made landfall near Buras, Louisiana, as a Category 4 hurricane. With wind speeds of about 233 kilometers per hour, a storm surge of 8.5 meters, and heavy rains, Katrina pounded the U.S. Gulf Coast states of Alabama, Louisiana, and Mississippi with lifethreatening flooding and destruction. Katrina's high winds and storm surge breached the levees protecting New Orleans, a city located below sea level, and flooded approximately 80% of the city. Katrina also caused major damage to the region's oil and natural gas production and refining capabilities. On 2 September 2005, the Associated Press reported that Katrina had damaged 58 oil platforms, 30 of which were reported lost; one damaged platform had been blown nearly 100 km from its original location.

Eos, Earth and Space Science News↗

USGS2007

Climate change and disturbance interactions: Workshop on climate change and disturbance interactions in western North America, Tucson, Ariz., 12-15 February 2007

Warming temperatures across western North America, coupled with increased drought, are expected to exacerbate disturbance regimes, particularly wildfires, insect outbreaks, and invasions of exotic species. Many ecologists and resource managers expect ecosystems to change more rapidly from disturbance effects than from the effects of a changing climate by itself. A particular challenge is to understand the interactions among disturbance regimes; for example, how will massive outbreaks of bark beetles, which kill drought-stressed trees by feeding on cambial tissues, increase the potential for large severe wildfires in a warming climate? Researchers in climatology, ecosystem science, fire and insect ecology, and landscape modeling from across western North America convened in Tucson, Ariz., for a 2 and a half day intensive workshop to identify new research directions in climate change and disturbance ecology. Four work groups focused on different aspects of the response of disturbance regimes to climate change: (1) extreme events and climatic variability (2) the effects of changing disturbance regimes on ecosystems, (3) disturbance interactions and cumulative effects, and (4) developing new landscape disturbance models. The workshop was structured with the analytic hierarchy process, a decision support method for achieving consensus from diverse groups of experts without sacrificing individual contributions.

Eos, Earth and Space Science News↗

USGS2011

Critical steps for the continuing advancement of hydrogeophysics

Special hydrogeophysics issues published by hydrology and geophysics journals, special sessions and workshops at conferences, and an increasing number of short courses demonstrate the growing interest in the use of geophysics for hydrologic investigations. The formation of the hydrogeophysics technical subcommittee of AGU's Hydrology section adds further evidence of the recognized significance of this growing interdisciplinary field. Given the clear value of nondestructive and nonintrusive imaging for subsurface investigations, we believe the advances in the adoption of existing geophysical methods, the development of novel methods, and the merging of geophysical and other data made in hydrogeophysics could be applied to a wide range of geological, environmental, and engineering applications.

Eos Science News↗

USGS2011

Modeling hazardous mass flows Geoflows09: Mathematical and computational aspects of modeling hazardous geophysical mass flows; Seattle, Washington, 9–11 March 2009

A recent workshop at the University of Washington focused on mathematical and computational aspects of modeling the dynamics of dense, gravity-driven mass movements such as rock avalanches and debris flows. About 30 participants came from seven countries and brought diverse backgrounds in geophysics; geology; physics; applied and computational mathematics; and civil, mechanical, and geotechnical engineering. The workshop was cosponsored by the U.S. Geological Survey Volcano Hazards Program, by the U.S. National Science Foundation through a Vertical Integration of Research and Education (VIGRE) in the Mathematical Sciences grant to the University of Washington, and by the Pacific Institute for the Mathematical Sciences. It began with a day of lectures open to the academic community at large and concluded with 2 days of focused discussions and collaborative work among the participants.

Eos, Earth and Space Science News↗

USGS2011

Exploring active tectonics in the Dominican Republic

The devastating 12 January 2010 Haiti earthquake ( M = 7.0), which killed an estimated 230,000 people and caused extensive damage to homes and buildings, drew attention to the crucial need for improved knowledge of the active tectonics of the Caribbean region. But even before this disastrous event, interest in understanding the active and complex northeastern Caribbean plate boundary had been increasing, because this region has experienced significant seismic activity during the past century and has an extensively documented record of historical seismicity and tsunamis. Moreover, this is an easily accessible region in which to study the continuity of seismic faults offshore and to try to understand the transitions between strike-slip and convergent tectonic regimes. Interest in the region has led to several studies that have improved scientists' knowledge of subduction zone tectonics and earthquake and tsunami hazard assessments [ Mann et al., 2002; ten Brink et al., 2006, 2009; Grindlay et al., 2005; Manaker et al., 2008; Granja Bruña et al., 2009; Mondziel et al., 2010].

Eos Science News↗

USGS2011

Space geodetic data improve seismic hazard assessment in California: Workshop on incorporating geodetic surface deformation data Into UCERF3; Pomona, California, 1–2 April 2010

A workshop was held to begin scientific consideration of how to incorporate space geodetic constraints on strain rates and fault slip rates into the next generation Uniform California Earthquake Rupture Forecast, version 3 (UCERF3), due to be completed in mid-2012. Principal outcomes of the meeting were (1) an assessment of secure science ready for UCERF3 applications within the next year, and (2) an agenda of new research objectives for the Southern California Earthquake Center (SCEC), the U.S. Geological Survey (USGS), and others in support of UCERF3 and related probabilistic seismic hazard assessments (PSHA). A number of goals potentially achievable within a year were identified, including (1) slip rate and fault locking depth estimates, with uncertainties or ranges, for all major and some minor faults of the extended San Andreas system; (2) strain rate estimates or bounds on rates for selected regions lying off the major faults of the San Andreas system; and (3) corrections or bounds on perturbing effects of postseismic deformation and elastic modulus heterogeneities on the observed Global Positioning System (GPS) velocity field (needed as input to models for estimating fault slip and strain rates in goals 1 and 2 above).

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USGS2011

Observing the Greatest Earthquakes: AGU Chapman Conference on Giant Earthquakes and Their Tsunamis: Viña del Mar and Valparaíso, Chile, 16–20 May 2010

An AGU Chapman Conference commemorated the fiftieth anniversary of the 1960 M 9.5 Chile earthquake. Participants reexamined this earthquake, the largest ever recorded instrumentally, and compared it with Chile's February 2010 M 8.8 earthquake. They also addressed the giant earthquake potential of subduction zones worldwide and strategies for reducing losses due to tsunamis. The conference drew 96 participants from 18 countries, and it reached out to public audiences in Chile.

Eos, Earth and Space Science News↗

USGS2015

Keeping watch over Colombia’s slumbering volcanoes

Located in the Central Cordillera (Colombian Andes), Nevado del Ruiz is a volcanic complex, topped by glaciers, rising 5,321 m above sea level. A relatively small explosive eruption from Ruiz's summit crater on November 13, 1985, generated an eruption column and sent a series of pyroclastic flows and surges across the volcano's ice-covered summit. Pumice and meltwater produced by the hot pyroclastic flows and surges swept into gullies and channels on the slopes of Ruiz as a series of lahars. Within two hours of the beginning of the eruption, lahars had traveled 100 km and left behind a wake of destruction: more than 25,000 people were killed (23,000 in the town of Armero and 2,000 in the town of Chinchiná), about 5,000 injured, and more than 5,000 homes destroyed along the Chinchiná, Gualí, and Lagunillas rivers.

Nevado del Ruiz↗

USGS2015

Building sandbars in the Grand Canyon

In 1963, the U.S. Department of the Interior’s Bureau of Reclamation finished building Glen Canyon Dam on the Colorado River in northern Arizona, 25 kilometers upstream from Grand Canyon National Park. The dam impounded 300 kilometers of the Colorado River, creating Lake Powell, the nation’s second largest reservoir. By 1974, scientists found that the downstream river’s alluvial sandbars were eroding because the reservoir trapped the fine sediment that replenished the deposits during annual floods. These sandbars are important structures for many kinds of life in and along the river. Now, by implementing a new strategy that calls for repeated releases of large volumes of water from the dam, the U.S. Department of the Interior (DOI) seeks to increase the size and number of these sandbars. Three years into the "high-flow experiment" (HFE) protocol, the releases appear to be achieving the desired effect. Many sandbars have increased in size following each controlled flood, and the cumulative results of the first three releases suggest that sandbar declines may be reversed if controlled floods can be implemented frequently enough.

Eos, Earth and Space Science News↗