West Antarctic Rift System

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Map of Antarctica showing West Antarctic Rift System in rose shading Antarctica continent and West Antarctic Rift.svg
Map of Antarctica showing West Antarctic Rift System in rose shading

The West Antarctic Rift System is a series of rift valleys between East and West Antarctica. [1] It encompasses the Ross Embayment, the Ross Sea, the area under the Ross Ice Shelf and a part of Marie Byrd Land in West Antarctica, [2] reaching to the base of the Antarctic Peninsula. [1] It has an estimated length of 3,000 km (1,900 mi) and a width of approximately 700 km (430 mi). [1] Its evolution is due to lithospheric thinning of an area of Antarctica that resulted in the demarcation of East and West Antarctica. The scale and evolution of the rift system has been compared to that of the Basin and Range Province of the Western United States. [1] [3]

Contents

Geology

West Antarctic Rift System (between red dash lines). Dots are geologic drill holes. Insert map shows approximate extent. Map of West Antarctic Rift (WARS).svg
West Antarctic Rift System (between red dash lines). Dots are geologic drill holes. Insert map shows approximate extent.

Exploration of the geology of the West Antarctic Rift System is limited because apart from peaks of the Transantarctic Mountains that protrude above the ice, much of the region is covered by the Ross Ice Shelf and the vast West Antarctic Ice Sheet. Several mountain ranges are located at the eastern boundary in Marie Byrd Land. [4] Consequently, the rift is less well known than other major rift valley systems. It is known that like the East African Rift, the West Antarctic Rift System comprises a number of much shorter rifts that cross Antarctica. Beneath the floor of the Ross Sea four rift basins have been detected by marine seismic reflections surveys. [5] Rift basins have been mapped under the West Antarctic Ice Sheet [6] including the Bentley Subglacial Trench.

Evolution

Rifting began in the Late Cretaceous as a result of tectonic extension (stretching and thinning of the crust and mantle) in approximately an east–west orientation, by plate tectonics processes. [7] The extension within the Ross Embayment occurred over four time periods and totals 500 kilometers or more, [7] mostly before the late Miocene. [8] The first phase happened in the east near Marie Byrd Land [4] before the Campbell Plateau of Zealandia broke away from Antarctica in the Late Cretaceous. [9]

A second phase during the Late Cretaceous and Paleocene extended the central areas of the embayment. [10] [7] This extension was at least 130 kilometers. [7]

A third phase is related to 170–180 kilometers of Eocene and Oligocene seafloor spreading in the western parts of the embayment on the Adare Trough or basin in the deep-sea. [11] [12] This episode of sea floor spreading created the ocean crust that now underlies much of the Northern Basin. [13] [12] This phase also resulted in extension of the Victoria Land Basin (95 km [12] [14] ).

A small amount of extension (~7 kilometers) occurred in the Adare basin [15] and Victoria Land Basin (10-15 kilometers) in a fourth phase during Miocene time. [16] Displacement including minor extension in the western WARS and Ross Embayment computed from reconstruction of oceanic magnetic anomalies ended 11 million years ago. [8]

During the Eocene to Miocene clockwise relative rotation of West Antarctica with respect to East Antarctica resulted in extension in the western Ross Embayment but contraction, in Marie Byrd Land of West Antarctica. [8] Subsidence to form the present topography of the embayment continued through the Cenozoic as the extended crust and mantle under the Ross Embayment cooled. [7] Faulting within the Terror Rift, located in the Victoria Land Basin, continued after 11 Ma, and probably into or through Quaternary time. [17]  

Although most rifts within the West Antarctic Rift System are no longer active, geodetic surveys show that West Antarctica is moving away from East Antarctica in a north/northeasterly direction (approximately in the direction of the South Georgia Islands) at a rate of not greater than 1-2 millimetres per year (0.079 in/year) or 500,000 years per kilometre (800,000 years per mile). [18]

The West Antarctic Rift System is the source of all the recently active volcanoes within Antarctica and all the recently active volcanoes on the continent. [19] [20] It is responsible for most of the major mountain systems outside the Antarctic Peninsula. Volcanism has been attributed to the rifting and also a mantle hotspot. [21]

Glaciology

The WARS is also believed to have a major influence on ice flows in West Antarctica. In western Marie Byrd Land active glaciers flow through fault-bounded valleys (grabens) of the WARS. [2] Sub-ice volcanism has been detected and proposed to influence ice flow. [22] Fast-moving ice streams in the Siple Coast adjacent to the east edge of the Ross Ice Shelf are influenced by the lubrication provided by water-saturated till within fault-bounded grabens within the rift, [23] [24] which could cause rapid breakup of the ice sheet if global warming accelerates. [25]

Related Research Articles

<span class="mw-page-title-main">Geography of Antarctica</span> Geographic features of Antarctica

The geography of Antarctica is dominated by its south polar location and, thus, by ice. The Antarctic continent, located in the Earth's southern hemisphere, is centered asymmetrically around the South Pole and largely south of the Antarctic Circle. It is washed by the Southern Ocean or, depending on definition, the southern Pacific, Atlantic, and Indian Oceans. It has an area of more than 14 million km2. Antarctica is the largest ice desert in the world.

<span class="mw-page-title-main">Ross Sea</span> Deep bay of the Southern Ocean in Antarctica

The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who visited this area in 1841. To the west of the sea lies Ross Island and Victoria Land, to the east Roosevelt Island and Edward VII Peninsula in Marie Byrd Land, while the southernmost part is covered by the Ross Ice Shelf, and is about 200 miles (320 km) from the South Pole. Its boundaries and area have been defined by the New Zealand National Institute of Water and Atmospheric Research as having an area of 637,000 square kilometres (246,000 sq mi).

<span class="mw-page-title-main">Amundsen Sea</span> Arm of the Southern Ocean

The Amundsen Sea, an arm of the Southern Ocean off Marie Byrd Land in western Antarctica, lies between Cape Flying Fish to the east and Cape Dart on Siple Island to the west. Cape Flying Fish marks the boundary between the Amundsen Sea and the Bellingshausen Sea. West of Cape Dart there is no named marginal sea of the Southern Ocean between the Amundsen and Ross Seas. The Norwegian expedition of 1928–1929 under Captain Nils Larsen named the body of water for the Norwegian polar explorer Roald Amundsen while exploring this area in February 1929.

<span class="mw-page-title-main">West Antarctic Ice Sheet</span> Segment of the continental ice sheet that covers West (or Lesser) Antarctica

The Western Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.

<span class="mw-page-title-main">Marie Byrd Land</span> Unclaimed West Antarctic region

Marie Byrd Land (MBL) is an unclaimed region of Antarctica. With an area of 1,610,000 km2 (620,000 sq mi), it is the largest unclaimed territory on Earth. It was named after the wife of American naval officer Richard E. Byrd, who explored the region in the early 20th century.

<span class="mw-page-title-main">Mount Moulton</span> Mountain in Antarctica

Mount Moulton is a 40-kilometre-long (25 mi) complex of ice-covered shield volcanoes, standing 25 kilometres (16 mi) east of Mount Berlin in the Flood Range, Marie Byrd Land, Antarctica. It is named for Richard S. Moulton, chief dog driver at West Base. The volcano is of Pliocene age and is presently inactive.

<span class="mw-page-title-main">Mount Takahe</span> Shield volcano in the Antarctica

Mount Takahe is a 3,460-metre-high (11,350 ft) snow-covered shield volcano in Marie Byrd Land, Antarctica, 200 kilometres (120 mi) from the Amundsen Sea. It is a c. 30-kilometre-wide (19 mi) mountain with parasitic vents and a caldera up to 8 kilometres (5 mi) wide. Most of the volcano is formed by trachytic lava flows, but hyaloclastite is also found. Snow, ice, and glaciers cover most of Mount Takahe. With a volume of 780 km3 (200 cu mi), it is a massive volcano; the parts of the edifice that are buried underneath the West Antarctic Ice Sheet are probably even larger. It is part of the West Antarctic Rift System along with eighteen other known volcanoes.

<span class="mw-page-title-main">Toney Mountain</span> Shield volcano in the Antarctic

Toney Mountain is an elongated snow-covered shield volcano, 60 km (37 mi) long and rising to 3,595 m (11,795 ft) at Richmond Peak, located 56 km (35 mi) southwest of Kohler Range in Marie Byrd Land, Antarctica.

<span class="mw-page-title-main">Crary Mountains</span> Volcanoes in Antarctica

Crary Mountains are a group of ice-covered volcanoes in Marie Byrd Land, Antarctica. They consist of two or three shield volcanoes, named Mount Rees, Mount Steere and Mount Frakes, which developed during the course of the Miocene and Pliocene and last erupted about 30,000-40,000 years ago. The first two volcanoes are both heavily incised by cirques, while Mount Frakes is better preserved and has a 4 kilometres (2.5 mi) wide caldera at its summit. Boyd Ridge is another part of the mountain range and lies southeast of Mount Frakes; it might be the emergent part of a platform that underlies the mountain range.

<span class="mw-page-title-main">Fosdick Mountains</span> Mountain range in Marie Byrd Land, Antarctica

The Fosdick Mountains are an east–west trending mountain range with marked serrate outlines, standing along the south side of Balchen Glacier at the head of Block Bay, in the Ford Ranges of Marie Byrd Land, Antarctica. They were discovered by the Byrd Antarctic Expedition in 1929, and named by Richard E. Byrd for Raymond B. Fosdick, who became president of the Rockefeller Foundation.

<span class="mw-page-title-main">Cape Colbeck</span> Headland of Antarctica

Cape Colbeck is a prominent ice-covered cape which forms the northwestern extremity of the Edward VII Peninsula and Marie Byrd Land in Antarctica. It was discovered in January 1902 by the British National Antarctic Expedition and named for Captain William Colbeck, Royal Naval Reserve, who commanded Robert Scott's relief ship, the Morning.

<span class="mw-page-title-main">Geology of Antarctica</span> Geologic composition of Antarctica

The geology of Antarctica covers the geological development of the continent through the Archean, Proterozoic and Phanerozoic eons.

<span class="mw-page-title-main">Shetland Plate</span> Tectonic microplate off the tip of the Antarctic Peninsula

The Shetland Plate, or South Shetland Plate, is a tectonic microplate located off the tip of the Antarctic Peninsula that contains the South Shetland Islands. The plate is bordered on three sides by the Antarctic Plate, while the fourth side is bordered by the Scotia Plate. The northwestern border is defined by the South Shetland Trench, separating the Shetland Plate to the south from the Antarctic Plate to the north. This trench is the remnant of a subduction zone where the defunct Phoenix Plate, now part of the Antarctic Plate, subducted under the Antarctic Peninsula and the Shetland Islands. The southeastern border is a rift zone, with the Antarctic Plate creating the Bransfield Basin. The southwestern and northeastern boundaries are each part of larger fracture zones. The southwestern border is the Hero Fracture Zone and separates the Antarctic Plate to the southwest from the Shetland Plate to the northeast. The northeastern boundary is the Shackleton Fracture Zone and separates the Shetland Plate to the southwest from the Scotia Plate.

The Erebus hotspot is a volcanic hotspot responsible for the high volcanic activity on Ross Island in the western Ross Sea of Antarctica. Its current eruptive zone, Mount Erebus, has erupted continuously since its discovery in 1841. Magmas of the Erebus hotspot are similar to those erupted from hotspots at the active East African Rift in eastern Africa. Mount Bird at the northernmost end of Ross Island and Mount Terror at its eastern end are large basaltic shield volcanoes that have been potassium-argon dated 3.8–4.8 and 0.8–1.8 million years old.

Phillips Mountains is a range of mountains on the north side of Balchen Glacier and Block Bay in the Ford Ranges, Marie Byrd Land, West Antarctica. Discovered by the Byrd Antarctic Expedition (1928–30) and named by Byrd for Albanus Phillips, Sr., a manufacturer in Cambridge, Maryland, United States, and patron of the Byrd expeditions.

<span class="mw-page-title-main">East Antarctic Shield</span> Cratonic rock body which makes up most of the continent Antarctica

The East Antarctic Shield or Craton is a cratonic rock body that covers 10.2 million square kilometers or roughly 73% of the continent of Antarctica. The shield is almost entirely buried by the East Antarctic Ice Sheet that has an average thickness of 2200 meters but reaches up to 4700 meters in some locations. East Antarctica is separated from West Antarctica by the 100–300 kilometer wide Transantarctic Mountains, which span nearly 3,500 kilometers from the Weddell Sea to the Ross Sea. The East Antarctic Shield is then divided into an extensive central craton that occupies most of the continental interior and various other marginal cratons that are exposed along the coast.

<span class="mw-page-title-main">Adare Basin</span>

The Adare Basin is a geologic structural basin located north-east of Cape Adare of Antarctica, for which its named, and north of the western Ross Sea. The Adare Basin is an extensional rift basin located along a seafloor spreading center that forms the failed arm of the Tertiary spreading ridge separating East and West Antarctica, known as the West Antarctic Rift System and similar in structure to the East Africa Rift System. Centrally located in the Adare Basin is the Adare Trough. The extension of this rift system is recorded in a series of magnetic anomalies which run along the seafloor at the extinct, north–south trending, Adare spreading axis. The Adare spreading system continues unbroken into the Northern Basin underlying the adjacent Ross Sea continental shelf.

<span class="mw-page-title-main">Christine Siddoway</span> American Antarctic researcher

Christine Siddoway is an American Antarctic researcher, best known for her work on the geology and tectonics of the Ford Ranges in western Marie Byrd Land. Other discoveries relate to preserved records of continental-interior sedimentation during the Sturtian glaciation, Cryogenian Period, in Rodinia, and evidence of a reduced Pliocene extent of the West Antarctic ice sheet, based upon investigation of clasts transported to/deposited in deep water by Ice rafting in the Amundsen Sea.

<span class="mw-page-title-main">Bruce P. Luyendyk</span> American geophysicist and oceanographer (born 1943)

Bruce Peter Luyendyk is an American geophysicist and oceanographer, currently professor emeritus of marine geophysics at the University of California, Santa Barbara. His work spans marine geology of the major ocean basins, the tectonics of southern California, marine hydrocarbon seeps, and the tectonics and paleoclimate of Antarctica. His research includes tectonic rotations of the California Transverse Ranges, participation in the discovery of deep-sea hydrothermal vents, quantitative studies of marine hydrocarbon seeps, and geologic exploration of the Ford Ranges in Marie Byrd Land, Antarctica.

<span class="mw-page-title-main">Ross Embayment</span> Region of Antarctica

The Ross Embayment is a large region of Antarctica, comprising the Ross Ice Shelf and the Ross Sea, that lies between East and West Antarctica.

References

  1. 1 2 3 4 Behrendt, J.C.; LeMasurier, W.E.; Cooper, A.K.; Tessensohn, F.; Tréhu, A.; Damaske, D. (1991). "Geophysical studies of the West Antarctic Rift System". Tectonics. 10 (6): 1257–1273. Bibcode:1991Tecto..10.1257B. doi:10.1029/91TC00868.
  2. 1 2 Luyendyk, Bruce P.; Wilson, Douglas S.; Siddoway, Christine S. (1 October 2003). "Eastern margin of the Ross Sea Rift in western Marie Byrd Land, Antarctica: Crustal structure and tectonic development". Geochemistry, Geophysics, Geosystems. 4 (10): 1090. Bibcode:2003GGG.....4.1090L. doi: 10.1029/2002GC000462 . ISSN   1525-2027.
  3. ↑ Tessensohn, F., and G. Wörner. 1991. "The Ross Sea rift system, Antarctica: structure, evolution and analogues." In Geological Evolution of Antarctica, edited by M.R.A. Thomson, J.A. Crame and J.W. Thomson, 273–277. Cambridge University Press.
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  6. ↑ Bell, R.E., M. Studinger, Karner G., Finn C.A., and D.D.  Blankenship. 2006. "Identifying Major Sedimentary Basins Beneath the West Antarctic Ice Sheet from Aeromagnetic Data Analysis." In Antarctica. , edited by Fütterer D.K., Damaske D., Kleinschmidt G., Miller H. and Tessensohn F., 117–121. Berlin, Heidelberg: Springer.
  7. 1 2 3 4 5 Wilson, Douglas S.; Luyendyk, Bruce P. (1 August 2009). "West Antarctic paleotopography estimated at the Eocene-Oligocene climate transition". Geophysical Research Letters. 36 (16). Bibcode:2009GeoRL..3616302W. doi:10.1029/2009GL039297. ISSN   1944-8007. S2CID   163074.
  8. 1 2 3 Granot, Roi; Dement, Jérôme (9 August 2018). "Late Cenozoic unification of East and West Antarctica". Nature Communications. 9 (1): 3189. Bibcode:2018NatCo...9.3189G. doi:10.1038/s41467-018-05270-w. ISSN   2041-1723. PMC   6085322 . PMID   30093679.
  9. ↑ Lawver, L. A., and L. M. Gahagan. 1994. "Constraints on timing of extension in the Ross Sea region."  Terra Antartica1:545–552.
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  12. 1 2 3 Granot, R.; Cande, S. C.; Stock, J. M.; Damaske, D. (28 January 2013). "Revised Eocene-Oligocene kinematics for the West Antarctic rift system" (PDF). Geophysical Research Letters. 40 (2): 279–284. Bibcode:2013GeoRL..40..279G. doi: 10.1029/2012GL054181 . ISSN   1944-8007.
  13. ↑ Davey, F. J.; Granot, R.; Cande, S. C.; Stock, J. M.; Selvans, M.; Ferraccioli, F. (28 June 2016). "Synchronous oceanic spreading and continental rifting in West Antarctica" (PDF). Geophysical Research Letters. 43 (12): 6162–6169. Bibcode:2016GeoRL..43.6162D. doi:10.1002/2016GL069087. ISSN   1944-8007. S2CID   41698490.
  14. ↑ Davey, F. J.; Cande, S. C.; Stock, J. M. (1 October 2006). "Extension in the western Ross Sea region-links between Adare Basin and Victoria Land Basin" (PDF). Geophysical Research Letters. 33 (20). Bibcode:2006GeoRL..3320315D. doi: 10.1029/2006GL027383 . ISSN   1944-8007.
  15. ↑ Granot, R.; Cande, S. C.; Stock, J. M.; Davey, F. J.; Clayton, R. W. (1 August 2010). "Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences" (PDF). Geochemistry, Geophysics, Geosystems. 11 (8): n/a. Bibcode:2010GGG....11.8005G. doi: 10.1029/2010GC003105 . ISSN   1525-2027.
  16. ↑ Henrys, Stuart; et al. (16 July 2007). "USGS Open-File Report 2007-1047, Short Research Paper 049". Tectonic History of Mid-Miocene to Present Southern Victoria Land Basin, Inferred from Seismic Stratigraphy in McMurdo Sound, Antarctica. 2007 (1047srp049). doi:10.3133/of2007-1047.srp049. ISSN   0196-1497.
  17. ↑ Sauli, C., C. C. Sorlien, M. Busetti, L. De Santis, N. Wardell, S. Henrys, R. Geletti, T. Wilson, B. Luyendyk, 2015, Neogene development of Terror Rift, western Ross Sea, Antarctica, Abstract T51F-2965 presented at 2015 Fall Meeting, AGU, San Francisco, Calif., 14–18 Dec.
  18. ↑ Donnellan, Andrea; Luyendyk, Bruce (1 July 2004). "GPS evidence for a coherent Antarctic plate and for postglacial rebound in Marie Byrd Land". Global and Planetary Change. 42 (1–4): 305–311. Bibcode:2004GPC....42..305D. doi:10.1016/j.gloplacha.2004.02.006. ISSN   0921-8181.
  19. ↑ LeMasurier, W.E.; Thomson, J.W.; Baker, P.E.; Kyle, P.R.; Rowley, P.D.; Smellie, J.L.; Verwoerd, W.J., eds. (1990). Volcanoes of the Antarctic Plate and Southern Oceans. Antarctic Research Series. Vol. 48. doi:10.1029/ar048. ISBN   978-0-87590-172-5. ISSN   0066-4634.
  20. ↑ van Wyk de Vries, Maximillian; Bingham, Robert G.; Hein, Andrew S. (29 May 2017). "A new volcanic province: an inventory of subglacial volcanoes in West Antarctica". Geological Society, London, Special Publications. 461 (1): 231–248. doi: 10.1144/sp461.7 . ISSN   0305-8719.
  21. ↑ Winberry, J. Paul; Anandakrishnan, Sridhar (1 November 2004). "Crustal structure of the West Antarctic rift system and Marie Byrd Land En Daarom was Ian Tolliehotspot". Geology. 32 (11): 977–980. Bibcode:2004Geo....32..977W. doi:10.1130/G20768.1. ISSN   0091-7613.
  22. ↑ Blankenship, Donald D.; Bell, Robin E.; Hodge, Steven M.; Brozena, John M.; Behrendt, John C.; Finn, Carol A. (1993). "Active volcanism beneath the West Antarctic ice sheet and implications for ice-sheet stability". Nature. 361 (6412): 526–529. Bibcode:1993Natur.361..526B. doi:10.1038/361526a0. ISSN   1476-4687. S2CID   4267792.
  23. ↑ Studinger, Michael; Bell, Robin E.; Blankenship, Donald D.; Finn, Carol A.; Arko, Robert A.; Morse, David L.; Joughin, Ian (15 September 2001). "Subglacial sediments: A regional geological template for ice flow in West Antarctica". Geophysical Research Letters. 28 (18): 3493–3496. Bibcode:2001GeoRL..28.3493S. doi: 10.1029/2000GL011788 . ISSN   1944-8007.
  24. ↑ Peters, Leo E.; Anandakrishnan, Sridhar; Alley, Richard B.; Winberry, J. Paul; Voigt, Donald E.; Smith, Andrew M.; Morse, David L. (1 January 2006). "Subglacial sediments as a control on the onset and location of two Siple Coast ice streams, West Antarctica". Journal of Geophysical Research: Solid Earth. 111 (B1). Bibcode:2006JGRB..111.1302P. doi: 10.1029/2005JB003766 . ISSN   2156-2202.
  25. ↑ Veen, C. J. Van Der; Whillans, I. M. (1993). "New and improved determinations of velocity of Ice Streams B and C, West Antarctica". Journal of Glaciology. 39 (133): 483–590. doi: 10.3189/S0022143000016373 . ISSN   1727-5652.

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