Publications

New gravity data reveal a prominent negative anomaly along the main vent axis of the northern Harrat Rahat volcanic field in Saudi Arabia. The low continues north of the volcanic field onto exposures of Proterozoic rocks, indicating that the low is caused not only by the volcanic field (and possibly also underlying Cenozoic sediments), but also the underlying Proterozoic basement. An...

Methane emissions regulate the near‐term global warming potential of permafrost thaw, particularly where loss of ice‐rich permafrost converts forest and tundra into wetlands. Northern latitudes are expected to get warmer and wetter, and while there is consensus that warming will increase thaw and methane emissions, effects of increased precipitation are uncertain. At a thawing wetland...

One of the desired outcomes of dam decommissioning and removal is the recovery of aquatic and riparian ecosystems. To investigate this common objective, we synthesized information from empirical studies and ecological theory into conceptual models that depict key physical and biological links driving ecological responses to removing dams. We define models for three distinct spatial...

The U.S. Geological Survey completed the first-ever global assessment of undiscovered copper resources for the two most significant sources of global copper supply: porphyry copper deposits and sediment-hosted stratabound copper deposits. The geology-based study identified 236 areas for undiscovered copper in 11 regions of the world. Estimated amounts of undiscovered copper resources are...

We have successfully applied of SH-wave seismic reflection methods to two different near-surface problems targeting unconsolidated sediments. At the former Fort Ord, where the water table is approximately 30m deep, we imaged aeolian and marine aquifer and aquitard stratigraphy to a depth of approximately 80m. We identified reflections from sand/clay and sand/silt interfaces and we mapped...

The U.S. Geological Survey is partnering with the IberoAmerican Association of Geological and Mining Surveys (ASGMI) to conduct an assessment of undiscovered metallic and non-metallic resources in the Greater Antilles region. The assessment plans to provide science-based information on the geologic availability of these resources for development, land-use planning, and decision making...

Maps are presented of extreme‐value geoelectric field amplitude and horizontal polarization for the Northeast United States. These maps are derived from geoelectric time series calculated for sites across the Northeast by frequency‐domain multiplication (time‐domain convolution) of 172 magnetotelluric impedance tensors, acquired during a survey, with decades‐long, 1‐min resolution time...

The northwest-trending Chocolate Mountains are situated along the northeastern margin of the southern Salton Trough. The Chocolate Mountain Aerial Gunnery Range occupies most of the 75-km-long part of the Chocolate Mountains that lies between Salt Creek to the north and California State Highway 78 to the south. Mapping studies in the Chocolate Mountains within the gunnery range are few...

In 2011 and 2012, the sedimentary basins in the Fort Irwin National Training Center, California, were evaluated for groundwater resources using a variety of techniques, including drilling of boreholes. This study summarizes lithostratigraphic features and deposits in 8 of 10 boreholes drilled in 2 basins located in the western part of Fort Irwin. The western part of Fort Irwin straddles...

The geology of the Fort Irwin National Training Center in the north-central Mojave Desert, California, provides insights into the hydrology and water resources of the area. The Fort Irwin area is underlain by rocks ranging in age from Proterozoic to Quaternary that have been deformed by faults as young as Quaternary. Pre-Tertiary sedimentary, igneous, and metamorphic bedrock and Miocene...

Geothermal systems occur where subsurface permeability and temperature are sufficiently high to drive fluid circulation. In the Great Basin region of the United States, which hosts ~20% of domestic geothermal electricity generation capacity and much of the projected undeveloped and undiscovered resource, crustal heat flow is relatively high, so permeability is the dominant factor...

The geologic structure beneath the Fallon Frontier Observatory for Research in Geothermal Energy (FORGE) site represents a record of the Mesozoic through Cenozoic tectonism, volcanism, and sedimentation that has affected the Carson Sink local to Fallon, NV. A robust dataset confirms that the lithologic sequence consists of Quaternary through Miocene sedimentary and volcanic rocks resting...