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USGS1997

Coastal-change and glaciological map of the Bakutis Coast, Antarctica

Changes in the area and volume of the polar ice sheets are intricately linked to changes in global climate, and the resulting changes in sea level may severely impact the densely populated coastal regions on Earth. Loss of the West Antarctic part of the Antarctic ice sheet alone could cause a sea-level rise of approximately 6 m. The potential sea-level rise after melting of the entire Antarctic ice sheet is estimated to be 65 m to 73 m. In spite of its importance, the mass balance (the net volumetric gain or loss) of the Antarctic ice sheet is poorly known; it is not known whether the ice sheet is growing or shrinking. As a result, measurement of changes in the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council (1986), by the Scientific Committee on Antarctic Research (SCAR) (1989), and by the National Science Foundation's (1990) Division of Polar Programs. An archive of early 1970's Landsat 1, 2, and 3 Multispectral Scanner (MSS) images of Antarctica and the fact that the repeat coverage with satellite images provided an excellent means of documenting changes in the coastline of Antarctica provided the impetus for carrying out a comprehensive analysis of the glaciological features of the coastal regions and changes in ice fronts of Antarctica. The project was later modified to include Landsat 4 and 5 MSS and Thematic Mapper (TM) and RADARSAT images to compare changes over a 20- to 25- year time interval and to prepare a series of 24 1:1,000,000-scale and 1 1:5,000,000-scale U.S. Geological Survey Geologic Investigations Series Maps ('I-Maps') (Williams and others, 1995; Williams and Ferrigno, 1998; and Ferrigno and others, 2002) in both paper and digital format.

IMAP↗

USGS2003

Coastal-change and glaciological map of the Bakutis Coast, Antarctica: 1972-2002

IMAP↗

USGS2007

Basement and crustal structure of the Davis Sea region (East Antarctica): implications for tectonic setting and continent to oceanic boundary definition

This study is based on about 8400 km of MCS, magnetic and gravity data as well as 20 sonobuoys collected by the Russian Antarctic Expedition during 2003 and 2004 in the Davis Sea and adjacent areas between 80°E and 102°E. Major tectonic provinces and features are identified and mapped in the study region including: 1) A marginal rift with a the extended continental crust ranging 130 to more than 200 km in width; 2) The marginal volcanic plateau of the Bruce Bank consisting of the Early Cretaceous igneous rocks; 3) The Early Cretaceous and Late Cretaceous−Paleogene oceanic basins; and 4) The Early Cretaceous igneous province of the Kerguelen Plateau. Four major horizons identified in the sedimentary cover of the Davis Sea region are attributed to main tectonic events and/or paleoenvironmental changes.

Open-File Report↗

USGS2013

Coastal-change and glaciological map of the Amery Ice Shelf area, Antarctica: 1961–2004

Reduction in the area and volume of Earth’s two polar ice sheets is intricately linked to changes in global climate and to the resulting rise in sea level. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council. On the basis of these recommendations, the U.S. Geological Survey used its archive of satellite images to document changes in the cryospheric coastline of Antarctica and analyze the glaciological features of the coastal regions. Amery Ice Shelf, lying between 67.5° and 75° East longitude and 68.5° and 73.2° South latitude, is the largest ice shelf in East Antarctica. The latest measurements of the area of the ice shelf range between 62,620 and 71,260 square kilometers. The ice shelf is fed primarily by Lambert, Mellor, and Fisher Glaciers; its thickness ranges from 3,000 meters in the center of the grounding line to less than 300 meters at the ice front. Lambert Glacier is considered to be the largest glacier in the world, and its drainage basin is more than 1 million square kilometers in area. It is possible to see some coastal change on the outlet glaciers along the coast, but most of the noticeable change occurs on the Amery Ice Shelf front.

IMAP↗

USGS2007

Aeromagnetic search for Cenozoic magmatism over the Admiralty Mountains Block (East Antarctica)

Cenozoic magmatic rocks of the Transantarctic Mountains provide an important window on the tectonic and magmatic processes of the West Antarctic Rift System. Previous aeromagnetic investigations in northern Victoria Land have delineated Cenozoic volcanic and intrusive complexes assigned to the McMurdo Volcanic Group and Meander Intrusives over the Transantarctic Mountains. We present a new aeromagnetic anomaly map for the region north of the Mariner Glacier to study the extent and spatial distribution of these Cenozoic rocks over the previously unexplored Admiralty Mountains. The new map shows that the Meander Intrusives are restricted to the coastal region between the Malta Plateau and the Daniell Peninsula. However, the McMurdo Volcanic Group rocks extend further inland, and may delineate a hitherto unrecognised volcano-tectonic rift zone, extending as far north as the Trafalgar Glacier.

Open-File Report↗

USGS2007

IGY to IPY, the U.S. Antarctic oversnow and airborne geophysical-glaciological research program from 1957 to 1964 from the view of a young graduate student

When 12 countries established scientific stations in Antarctica for the 1957-58 (IGY), the Cold War was at its height, seven countries had made claims in Antarctica, and the Antarctic Treaty was in the future. The only major field project of the U.S. IGY Antarctic program was series of oversnow traverses, starting in 1957, making seismic reflection ice soundings (and other geophysical measurements) and glaciological studies. The U.S.S.R. and France made similar traverses coordinated through the IGY. Although geology and topographic mapping were not part of the IGY program because of the claims issue and the possibility of mineral resources, the oversnow traverse parties did geologic work, during which unknown mountains were discovered. The oversnow traverses continued through 1966 and resulted in an excellent first approximation of the snow surface elevation, ice thickness and bed topography of Antarctica, as well as the mean annual temperature of that era and snow accumulation.

Open-File Report↗

USGS2005

Identifying major sedimentary basins beneath the West Antarctic ice sheet from aeromagnetic data analysis

In the Ross Sea, large sedimentary basins reflect primarily the major extensional event associated with the Late Cretaceous breakup of Gondwana. Within the Interior Ross Embayment, no similar large basins have been identified to date. We have used aerogravity and Werner deconvolution methods applied to aeromagnetic data to map depth to magnetic basement, which helped delineate three major sedimentary basins, the Bentley Subglacial, Onset, and Trunk D Basins.

Book chapter↗

USGS1996

Satellite imagery of the onset of streaming flow of ice streams C and D, West Antarctica

Five overlapping Landsat multispectral scanner satellite images of the interior of the West Antarctic ice sheet were enhanced with principal component analysis, high-pass filtering, and linear contrast stretching and merged into a mosaic by aligning surface features in the overlap areas. The mosaic was registered to geodetic coordinates, to an accuracy of about 1 km, using the five scene centers as control points. The onset of streaming flow of two tributaries of ice stream C and one tributary of ice stream D is visible in the mosaic. The onset appears to occur within a relatively short distance, less than the width of the ice stream, typically at a subglacial topographic feature, such as a step or ridge. The ice streams extend farther up into the interior than previously mapped. Ice stream D starts about 150 km from the ice divide, at an altitude of about 1500 m, approximately halfway up the convex-upward dome shape of the interior ice sheet. Ice stream D is relatively much longer than ice stream C, possibly because ice stream D is currently active, whereas ice stream C is currently inactive. The grounded portion of the West Antarctic ice sheet is perhaps best conceptualized as an ice sheet in which ice streams are embedded over most of its area, with slow-moving ice converging into fast-moving ice streams in a widely distributed pattern, much like that of streams and rivers in a hydrologic basin. A relic margin appears to parallel most of the south margin of the tributary of ice stream D, separated from the active shear margin by about 10 km or less for a distance of over 200 km. This means there is now evidence for recent changes having occurred in three of the five major ice streams which drain most of West Antarctica (B, C, and D), two of which (B and D) are currently active.

Journal of Geophysical Research C: Oceans↗

USGS2007

Tectonic history of mid-Miocene to present southern Victoria Land Basin, inferred from seismic stratigraphy in McMurdo Sound, Antarctica

New and existing seismic reflection data in southern McMurdo Sound have been used to investigate Neogene tectonic history of the Terror Rift adjacent to the Transantarctic Mountains and along the western margin of the West Antarctic Rift System. Seismic data image a young rifting episode that is largely unsampled by CRP and CIROS drill holes. Data reveal up to 3.5 km of post middle Miocene strata deposited in this part of the NNW- SSE trending Terror Rift basin. Mapped fault trends in the southern Terror Rift parallel the axis of the basin and are prominent in a 40 km wide zone north of Ross Island. Displacement on individual faults in this zone can exceed 100 m and faults collectively accommodate approximately 10-15 km of middle Miocene to recent extension.

Open-File Report↗

USGS1989

Gazetteer of the Antarctic

This gazetteer lists antarctic names approved by the United States Board on Geographic Names and by the Secretary of the Interior. The Board is the interagency body created by law to standardize and promulgate geographic names for official purposes. As the official standard for names in Antarctica, the gazetteer assures accuracy and uniformity for the specialist and the general user alike. Unlike the last (1981) edition, now out of print, the book contains neither historical notes nor textual descriptions of features. The gazetteer contains names of features in Antarctica and the area extending northward to the Antarctic Convergence that have been approved by the Board as recently as mid-1989. It supersedes previous Board gazetteers for the area. For each geographic feature, the book contains the name, cross references if any, and latitude and longitude. Coverage corresponds to that of maps at the scale of 1:250,000 or larger for islands, coastal Antarctica, and mountains and ranges of the continent. Much of the interior of Antarctica, an ice plateau, has been mapped at a smaller scale and is nearly devoid of features and toponyms. All of the names are for natural features; scientific stations are not listed. For the names of submarine features, reference should be made to the Gazetteer of Undersea Features, U.S. Board on Geographic Names (1981).

Report↗

USGS1997

Southern Laurentide ice lobes were created by ice streams: Des Moines Lobe in Minnesota, USA

Regional mapping in southern Minnesota has illuminated a suite of landforms developed by the Des Moines Lobe that delimit the position of the lobe at its maximum and at lesser readvances. The ice lobe repeatedly advanced, discharged its subglacial water, and subsequently stagnated. Recent glaciological research on Antarctic ice streams has led some glacial geologists to postulate that ice streams drained parts of the marine-based areas of the Laurentide Ice Sheet. I postulate that such ice streams may develop in land-based areas of an ice sheet as well, and that the Des Moines Lobe, 200 km wide and 900 km long, was an outlet glacier of an ice stream. It appears to have been able to advance beyond the Laurentide Ice Sheet as long as adequate water pressure was maintained. However, the outer part of the lobe stagnated because subglacial water that facilitated the flow was able to drain away through tunnel valleys. Stagnation of the lobe is not equivalent to stoppage of the ice stream, because ice repeatedly advanced into and onto the stagnant margins, stacking ice and debris. Similar landforms are also seen in other lobes of the upper midwestern United States.

Minnesota↗

USGS2007

Craddock Massif and Vinson Massif remeasured

The highest peak in Antarctica, the Vinson Massif (78º35’S, 85º25’W), is at an elevation of 4892 m (16,046 ft), as determined in 2004. Measurements of the elevation have fluctuated over the years, from its earliest surveyed elevation of 5140 m (16,859 ft), to its present height. Vinson Massif and three of its near neighbors in the Sentinel Range of the Ellsworth Mountains are the highest peaks in Antarctica, making them a favorite objective of mountaineers. Well over 1,100 people have climbed Vinson since the first ascent by a team in the 1966-67 austral summer. The range is composed of Crashsite quartzite, making the Sentinel’s very resistant to erosion. Very accurate elevations have been achieved annually by GPS mapping done by a climbing team sponsored by the Omega Foundation, active in Antarctica since 1998. The Craddock Massif now includes Mt. Craddock, the ninth highest peak in Antarctica, at 4368 m (14,327 ft). Both are named for Campbell Craddock*, a U.S. geologist active in Antarctic research beginning in 1959-60.

Open-File Report↗

USGS1995

Geographic names of the Antarctic

This gazetteer contains 12,710 names approved by the United States Board on Geographic Names and the Secretary of the Interior for features in Antarctica and the area extending northward to the Antarctic Convergence. Included in this geographic area, the Antarctic region, are the off-lying South Shetland Islands, the South Orkney Islands, the South Sandwich Islands, South Georgia, Bouvetøya, Heard Island, and the Balleny Islands. These names have been approved for use by U.S. Government agencies. Their use by the Antarctic specialist and the public is highly recommended for the sake of accuracy and uniformity. This publication, which supersedes previous Board gazetteers or lists for the area, contains names approved as recently as December 1994. The basic name coverage of this gazetteer corresponds to that of maps at the scale of 1:250,000 or larger for coastal Antarctica, the off-lying islands, and isolated mountains and ranges of the continent. Much of the interior of Antarctica is a featureless ice plateau. That area has been mapped at a smaller scale and is nearly devoid of toponyms. All of the names are for natural features, such as mountains, glaciers, peninsulas, capes, bays, islands, and subglacial entities. The names of scientific stations have not been listed alphabetically, but they may appear in the texts of some decisions. For the names of submarine features, reference should be made to the Gazetteer of Undersea Features , 4th edition, U.S. Board on Geographic Names, 1990.

Report↗

USGS1964

Distribution of narrow-width magnetic anomalies in Antarctica

Data for aeromagnetic profiles obtained in Antarctica during the 1963-64 austral summer were used together with earlier results to construct a map showing the areal distribution of narrow-width magnetic anomalies. Numerous anomalies are associated with known volcanic mountains in western Antarctica. A large area of few anomalies is probably a result of an extension of the thick metasedimentary section observed in the Ellsworth Mountains. Portions of the Trans-Antarctic Mountains have associated anomalies which are probably caused by late Cenozoic volcanic rocks.

Science↗

USGS1996

Patterns of late Cenozoic volcanic and tectonic activity in the West Antarctic rift system revealed by aeromagnetic surveys

Aeromagnetic surveys, spaced ≤5 km, over widely separated areas of the largely ice- and sea-covered West Antarctic rift system, reveal similar patterns of 100- to 1700-nT, shallow-source magnetic anomalies interpreted as evidence of extensive late Cenozoic volcanism. We use the aeromagnetic data to extend the volcanic rift interpretation over West Antarctica starting with anomalies over (1) exposures of highly magnetic, late Cenozoic volcanic rocks several kilometers thick in the McMurdo-Ross Island area and elsewhere; continuing through (2) volcanoes and subvolcanic intrusions directly beneath the Ross Sea continental shelf defined by marine magnetic and seismic reflection data and aeromagnetic data and (3) volcanic structures interpreted beneath the Ross Ice Shelf partly controlled by seismic reflection determinations of seafloor depth to (4) an area of similar magnetic pattern over the West Antarctic Ice Sheet (400 km from the nearest exposed volcanic rock), where interpretations of late Cenozoic volcanic rocks at the base of the ice are controlled in part by radar ice sounding. North trending magnetic rift fabric in the Ross Sea-Ross Ice Shelf and Corridor Aerogeophysics of the Southeast Ross Transect Zone (CASERTZ) areas, revealed by the aeromagnetic surveys, is probably a reactivation of older rift trends (late Mesozoic?) and is superimposed on still older crosscutting structural trends revealed by magnetic terrace maps calculated from horizontal gradient of pseudogravity. Long-wavelength (∼ 100-km wide) magnetic terraces from sources within the subvolcanic basement cross the detailed survey areas. One of these extends across the Ross Sea survey from the front of the Transantarctic Mountains with an east-southeast trend crossing the north trending rift fabric. The Ross Sea-Ross Ice Shelf survey area is characterized by highly magnetic northern and southern zones which are separated by magnetically defined faults from a more moderately magnetic central zone. Aeromagnetic data in the south delineate the Ross fault of unknown age. The extension of the southern Central Basin south of the Ross fault is associated with an 825-nT magnetic anomaly over the Ross Ice Shelf requiring inferred late Cenozoic volcanic rock essentially at the seafloor at its south end, as shown by magnetic models. Models show that the thickness of magnetic volcanic rocks beneath Hut Point Peninsula at McMurdo Station is probably <2 km. The detailed surveys, combined with data from > 100,000 km of widely spaced aeromagnetic profiles, led to the interpretation of the mostly subglacial West Antarctic flood basalts(?) or their subglacially erupted and intruded equivalent. The volume of the exposed volcanos is small in contrast to the much greater volume (> 10 6 km³) of late Cenozoic magmatic rock remaining at volcanic centers beneath the continental shelf, Ross Ice Shelf and West Antarctic Ice Sheet. We suggest as an alternative or supplemental explanation to the previously proposed mantle plume hypothesis for the late Cenozoic volcanism significantly greater lower lithosphere (mantle) stretching resulting in greater decompression melting than the limited Cenozoic crustal extension allows. However, this implies a space problem that is not obviously resolved, because the Antarctic Plate is essentially surrounded by spreading centers.

Tectonics↗

USGS1979

Surveying Antarctica: from dogsled to satellite

Base maps of Antarctica are needed at scales of 1:250,000 to plot scientific data, yet after 20 years of a major mapping effort, only about 20 percent of the continent has been accurately mapped using aerial photographs and ground surveys. Encompassing nearly 14.3 million square kilometers (5.5 million square miles), Antarctica still presents a formidable mapping task. Except for the area around the geographic South Pole, Landsat could, in just a few years, provide the images to planimetrically map Antarctica at such scales as 1:250,000. Just 11 Landsat images would encompass the same area mapped to date at a 1:250,000 scale. Navigation satellite data from ground stations can provide the necessary horizontal and vertical ground control in many areas. Other polar orbiting satellites could be used to establish elevation profiles of the ice surfaces on Antarctica. If this presently available space technology is fully utilized, the scientific exploration of the huge Antarctic continent will be greatly accelerated, fulfilling one of the goals Commander Byrd began to work toward 50 years ago.

Air and Space↗

USGS1991

Seismic stratigraphy and structure of Prydz Bay, Antarctica: Implications from Leg 119 drilling

Prydz Bay is situated on the MacRobertson Land coast of East Antarctica at the seaward end of a 700-km-long transverse rift zone, the Lambert Rift. New and reprocessed seismic reflection data are combined with drilling results from five Leg 119 sites across Prydz Bay to study the regional stratigraphy and structure of the continental shelf and upper slope. Severe seismic multiples hamper interpretations, yet seven acoustic units separated by unconformities can be distinguished regionally. Only four units (sedimentary) have been drilled. More than 5 km of well- to poorly-stratified units beneath the inner shelf fill the northeast-trending Prydz Bay basin, which is related to, but separated from, the Lambert Graben. Basinal units overlie metamorphic basement (unit PS.5) and are continental nonmarine deposits of possible late Paleozoic to early Mesozoic age (unit PS.4, Site 740) and Early Cretaceous and younger(?) age (unit PS.2B, Site 741). Seaward, the basin is flanked by a buried and intruded(?) basement ridge (units PS.5 and PS.6). Continuous to distorted reflections cover the ridge and dip seaward in a prograding unit (unit PS.2A) beneath the outer shelf. Glaciomarine rocks of late Eocene to early Oligocene age comprise the innermost part of the unit PS.2A (Sites 742 and 739) and Holocene glacial rocks the outermost (Site 743); ages of intermediate parts of the unit are unknown. A flatlying unit of chaotic to continuous reflectors directly beneath the seafloor covers most of the northeast shelf (unit PS. 1, Sites 740, 741, 742, and 739), and is composed of compacted glacial diamictites of late Miocene and younger age. We suspect that significant rifting and glacial events have caused acoustic disconformities beneath Prydz Bay. The principal rifting events began with earliest rifting of Gondwana in late Paleozoic time (units PS.5 to PS.4) and culminated with continental breakup in Early Cretaceous time (units PS.4 to PS.2B). The advent of East Antarctic glaciation in late Eocene to early Oligocene time (units PS.2B to PS.2A) and the grounding of ice sheets across the shelf in midand late-Cenozoic times (unit PS.l to underlying units) created the principal glacial disconformities. The seaward-prograding glacial sequences beneath the outermost shelf record numerous post-early Oligocene glacial events and likely sea-level changes that can only be partially mapped with existing seismic and drilling data.

Conference Paper↗

USGS2018

At-sea observations of marine birds and their habitats before and after the 2008 eruption of Kasatochi volcano, Alaska

Kasatochi volcano, an island volcano in the Aleutian chain, erupted on 7-8 August 2008. The resulting ash and pyroclastic flows blanketed the island, covering terrestrial habitats. We surveyed the marine environment surrounding Kasatochi Island in June and July of 2009 to document changes in abundance or distribution of nutrients, fish, and marine birds near the island when compared to patterns observed on earlier surveys conducted in 1996 and 2003. Analysis of SeaWiFS satellite imagery indicated that a large chlorophyll-a anomaly may have been the result of ash fertilization during the eruption. We found no evidence of continuing marine fertilization from terrestrial runoff 10 months after the eruption. At-sea surveys in June 2009 established that the most common species of seabirds at Kasatochi prior to the eruption, namely crested auklets (Aethia cristatella) and least auklets (Aethia pusilla) had returned to Kasatochi in relatively high numbers. Densities from more extensive surveys in July 2009 were compared with pre-eruption densities around Kasatochi and neighboring Ulak and Koniuji islands, but we found no evidence of an eruption effect. Crested and least auklet populations were not significantly reduced by the initial explosion and they returned to attempt breeding in 2009, even though nesting habitat had been rendered unusable. Maps of pre- and post-eruption seabird distribution anomalies indicated considerable variation, but we found no evidence that observed distributions were affected by the 2008 eruption. ?? 2010 Regents of the University of Colorado.

Arctic, Antarctic, and Alpine Research↗