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Geology topics

Peter W. Barnes

Publications and source records attributed to Peter W. Barnes.

At least 19 recordsLinked to original sources
USGS2005

Benthic habitats and the effects of fishing: Linking geology, biology, socioeconomics, and management in fisheries: An introduction

Fishery resource managers face the challenge of ensuring sustainable fisheries and maintaining healthy, diverse ecosystems. This challenge can be met by advancing the scientific knowledge available to resource managers to evaluate and appropriately manage fishing activities that affect benthic habitats. Government agencies have been working to develop benthic habitat research initiatives focused on the effects of fishing gear and the linkage between biological resources and the geology of benthic habitats. This book provides the broad understanding of the effects of fishing activities on benthic habitats necessary to address the pressing issues of habitat alteration that challenge managers, practitioners, and ocean scientists.

Conference Paper↗
USGS2000

U.S. Geological Survey coastal and marine geology research; recent highlights and achievements

The USGS Coastal and Marine Geology Program has large-scale national and regional research projects that focus on environmental quality, geologic hazards, natural resources, and information transfer. This Circular highlights recent scientific findings of the program, which play a vital role in the USGS endeavor to understand human interactions with the natural environment and to determine how the fundamental geologic processes controlling the Earth work. The scientific knowledge acquired through USGS research and monitoring is critically needed by planners, government agencies, and the public. Effective communication of the results of this research will enable the USGS Coastal and Marine Geology Program to play an integral part in assisting the Nation in responding the pressing Earth science challenges of the 21st century.

Circular↗
USGS2000

Map of Distribution of Bottom Sediments on the Continental Shelf, Gulf of Alaska

Introduction The U.S. Geological Survey has a long history of exploring marine geology in the Gulf of Alaska. As part of a cooperative program with other federal and state agencies, the USGS is investigating the relations between ocean-floor geology and benthic marine biohabitats. This bottom sediment map, compiled from published literature will help marine biologists develop an understanding of sea-floor geology in relation to various biological habitats. The pattern of sea-floor sedimentation and bottom morphology in the Gulf of Alaska reflects a complex interplay of regional tectonism, glacial advances and retreats, oceanic and tidal currents, waves, storms, eustatic change, and gravity-driven processes. This map, based on numerous cruises during the period of 1970-1996, shows distribution of bottom sediments in areas of study on the continental shelf. The samples were collected with piston, box, and gravity corers, and grab samplers. The interpretations of sediment distribution are the products of sediment size analyses combined with interpretations of high-resolution seismic reflection profiles. The sea floor was separated into several areas as follows: Cook Inlet -- Hazards studies in this embayment emphasized sediment distribution, sediment dynamics, bedforms, shallow faults, and seafloor stability. Migrating mega-sandwaves, driven by strong tidal currents, influence seabed habitats and stability of the seafloor, especially near pipelines and drilling platforms. The coarseness of the bottom sediment reinforces the influence of the strong tidal currents on the seafloor habitats. Kodiak Shelf -- Tectonic framework studies demonstrate the development of an accretionary wedge as the Pacific Plate underthrusts the Alaskan landmass. Seismic data across the accretionary wedge reveal anomalies indicative of fluid/gas vent sites in this segment of the continental margin. Geologic hazards research shows that movement along numerous shallow faults poses a risk to sea floor structures. Sea-floor sediment on shallow banks is eroded by seasonal wave-generated currents. The winnowing action of the large storm waves results in concentrations of gravel over broad segments of the Kodiak shelf. Northeastern Gulf of Alaska -- Tectonic framework studies demonstrate that rocks of distant origin (Yakutat terrane) are currently attached to and moving with the Pacific Plate, as it collides with and is subducted beneath southern Alaska. This collision process has led to pronounced structural deformation of the continental margin and adjacent southern Alaska. Consequences include rapidly rising mountains and high fluvial and glacial sedimentation rates on the adjacent margin and ocean floor. The northeastern Gulf of Alaska shelf also has concentrations of winnowed (lag) gravel on Tarr Bank and on the outer shelf southeast of Yakutat Bay. Between Kayak Island and Yakutat Bay the outer shelf consists of pebbly mud (diamict). This diamict is a product of glacial marine sedimentation during the Pleistocene and is present today as a relict sediment. A prograding wedge of Holocene sediment consisting of nearshore sand grading seaward into clayey silt and silty clay covers the relict pebbly mud to mid-shelf and beyond. Shelf and slope channel systems transport glacially derived sediment across the continental margin into Surveyor Channel, an abyssal fan and channel system that reaches over 1,000 km to the Aleutian Trench.

Miscellaneous Field Studies Map↗
USGS1995

Sea ice scouring on the inner shelf of the southeastern Canadian Beaufort Sea

About 2200 ice scours were observed and analyzed over a distance of approximately 500 km on the inner shelf of the southeastern Canadian Beaufort Sea. Ice scours were divided into two types based on their morphology: multiple scours consisting of a series of parallel scours and ridges, and single scours. Single scours are the dominant type representing more than 85% of the total observations. The mean scour depth and width are 0.3 m and 11 m respectively, but scour depths of more than 2 m and a scour width up to 345 m were documented. The magnitude of ice scouring processes increases with water depth. In water depths less than 10 m, less than 25% of the seafloor surface is reworked by ice scours. This percentage increases significantly seaward of the 10 m isobath, being more than 75% in water depths in excess of 12 m. A break in the seabed slope at about 10 to 12 m water depth marks a boundary between a nearshore zone moderately influenced by ice processes and an outer zone affected by intense ice scouring. This morphological boundary could be due to intense erosion by the keels of pressure ice ridges at the inner edge of a zone of grounded ice ridges. Most of the observed ice scours appear to be reworked, especially in water depths of less than 10 m, and represent small-scale sediment sinks. Inshore of the 10 m isobath, scour reworking is believed to be mainly due to frequent bottom disturbance by wave orbital currents and mean near-bottom flows during the open water season. Scour orientations show that the dominant motion of ice during scouring events is east or west, which is subparallel to the bathymetric contours and coastline. Scour terminal push mounds, however, suggest a dominant east to southeast movement that may contribute to onshore sediment transport during ice push events.

Northwest Territories, Yukon↗
USGS1995

Maps showing isotopic composition of methane in seawater of the Alaskan Beaufort Sea, 1994

We are engaged in a five-year study to test the hypothesis that methane from decomposing gas hydrates may contribute methane to the atmosphere. The release of methane, a "greenhouse" gas, can enhance global warming and be a factor in global climate change. As part of the study we have measured the methane concentration in the water column of the Beaufort Sea shelf out to water depths of 90 meters from 1992-1995. In 1994 the carbon isotopic composition of methane in seawater of the Beaufort Sea shelf from Cape Halkett to Mikkelsen Bay (total water depths from 3 to 56 m) was measured by gas chromatography-isotope-ratio mass spectrometry in an effort to define the source of methane. Concentrations of methane in water samples used for isotopic analysis ranged from 5.4 to 275 nM.

Alaska↗
USGS1991

Erosion and accretion along the arctic coast of Alaska. The influence of ice and climate

Coastline comparison on 1951 and 1981 charts to determine erosion and accretion showed that ocean-facing coastal bluffs were retreating while deltas were rapidly expanding. Where the coast is fronted by a lagoon, and coast-parallel sand and gravel islands, bluff retreat was reduced. The extensive bluff erosion was volumetrically balanced by accretion at the mouths of deltas. Coastal erosion is driven by ice-related processes, aided by the presence of an ice-eroded shelf. Rapid delta expansion is interpreted to have begun in the last 200 years, perhaps related to observed permafrost warming.

Conference Paper↗
USGS1990

Effects of elevated temperatures and rising sea level on Arctic Coast

Ice is a major agent on the inner shelf, gouging the bottom, increasing hydraulic scour, transporting sediment, and influencing river flood patterns. Rapid coastal retreat is common and low barrier islands and beaches are constantly changing due to the influence of permafrost, ice‐push, waves, and currents. Coastal processes are presently a balance between the influence of ice and the action of waves and currents. Quantitative values for processes are poorly known, however our qualitative understanding is nearly complete. Climatic warming and rising sea levels would decrease the temporal and aerial extent of coastal ice thereby expanding the role of waves and currents. As a result, shoreline retreat rates would increase, producing a transgressive erosional surface on the low coastal plain. With increased wave activity, beaches and barrier islands presently nourished by ice push processes would decay and disappear. Increased sediment supply from a deeply thawed, active layer would release more sediments to rivers and coasts. Additional research should be focused on permafrost and sea ice processes active during freeze up and breakup; the two seasons of most vigorous activity and change.

Journal of Cold Regions Engineering↗
USGS1982

Marine ice-pushed boulder ridge, Beaufort Sea, Alaska

A steep-faced boulder ridge up to 4m high by 300m long was encountered along the arctic coast east of Prudhoe Bay, Alaska, in the summer of 1979. Marine occurrences of similar ridges are rare. Since ice-push sorts cobble- and boulder-sized material in the construction of a ridge, recent onshore excursions of ice due to wind stress on the fast ice are believed to be responsible for building the boulder ridge. Ice push is a mechanism that preferentially sorts cobble- and boulder-sized material from 1-2m water depths and that forms boulder ridges in areas of high boulder concentrations.

Alaska↗
USGS1981

Ice-gouge data, Beaufort Sea, Alaska, 1972-1980

The interaction of sea ice with the sea floor is an important factor affecting geologic processes on high latitude shelves. One of the most obvious forms of this interaction is the formation of furrow-like gouges or the sea floor. These gouges are caused by wind- and current-driven ice masses that rake the seabed with their keels. Since the advent of side-scanning sonar about 1970, the morphology and character of these seabed features have been under study. Ice gouges have been reported from the Bering Sea (Thor and Nelson, 1980); from the Chukchi Sea (Rex, 1955; Toimil, 1978); from the Beaufort Sea off Alaska (Brooks, 1974; Carsola, 1954; Reimnitz et al., 1972); from the Beaufort Sea off Canada (Kindle, 1924; Lewis, 1978; Pelletier and Shearer, 1972; Wahlgren, 1979); from the east coast of Canada (Harris, 1974); from the northeast Atlantic (Belderson et al., 1973); and from the Great Lakes (Berkson and Clay, 1973).

Alaska↗