Visokoi Island

"Wordie Point" redirects here. For the site in the South Shetland Islands, see Point Wordie (South Shetland Islands).

Visokoi Island

South Sandwich Islands
Location of Visokoi Island
Geography
Coordinates	56°42′S27°09′W / 56.700°S 27.150°W / -56.700; -27.150 [1]
Archipelago	South Sandwich Islands
Length	8 km (5 mi)
Width	6 km (3.7 mi)
Highest elevation	1,005 m (3297 ft)
Highest point	Mount Hodson
Administration
United Kingdom
Demographics
Population	Uninhabited

Visokoi Island is an uninhabited volcanic island and one the three Traversay Islands that constitute a subgroup of the South Sandwich Islands, in the South Atlantic Ocean.

Visokoi consists of one major volcano, Mount Hodson whose height is usually given as 1,005 metres (3,297 ft). The mountain is mostly covered by glaciers, except for several low areas on the coast like the northern Finger Point and eastern Irving Point. Several parasitic vents are found especially on the eastern side, and one vent close to Finger Point is still hot. Eruptions were reported in 1830, 1927 and 1930.

Geography and geomorphology

Visokoi is one of the South Sandwich Islands, which lie southeast of South Georgia ^[2] in the Southern Ocean ^[3] and extend over a distance of 350 kilometres (220 mi) in north-south direction. ^[4] Leskov Island is 58 kilometres (36 mi) west and Zavodovski Island 45 kilometres (28 mi) north from Visokoi; ^[5] together they makes up the Traversay Islands ^[6] subgroup of the South Sandwich Islands. ^[2] Icebergs occur in the surrounding waters. ^[7]

The island has an oval shape with a length of 8 kilometres (5.0 mi) and a width of 6 kilometres (3.7 mi); ^[8] the surface area is about 30.7 square kilometres (11.9 sq mi). ^[9] The pointy end is east and ends at Irving Point, and the blunt end west with the western Sulphur Point and southwestern Wordie Point. The northernmost point is Finger Point and the southernmost Mikhaylov Point. ^[10] Cliffs and ice falls make up most of the coastline, except at Irving Point where there are an offshore reef and sandy beaches ^[5] and Finger Point which is a low-lying lava flow. ^[11] The island is asymmetric, with the western side having higher cliffs and steeper slopes than the eastern side. ^[12] Most of the inside of the island is covered with heavily crevassed ice, ^[8] which reaches the coast in several locations. ^[10] The total surface area covered by ice in 1962 amounted to 24.1 square kilometres (9.3 sq mi). ^[9] The 835 metres (2,740 ft) ^[13] or (more commonly mentioned) 1,005 metres (3,297 ft) high Mount Hodson rises on the western side of the island ^[10] and has a flat summit. ^[8] It features a 900 metres (3,000 ft) wide summit crater ^[14] surrounded by two concentric sector collapse scars. ^[15] Several scoria cones rise from the eastern part, including Shamrock Hill ^[8] and an unnamed but probably young cone ^[16] which form a nunatak. ^[10] They rise slightly above the ice level and bear no evidence of craters. ^[17]

Finger Point appears to consist of a lava flow with preserved surface features that extends northwards from the scree-covered slopes of Visokoi, forming a low-lying coastal platform. ^[18] Several islets lie around Visokoi, such as Coffin Rock off the northeastern coast. ^[10] The island is surrounded by a 2.3–6 kilometres (1.4–3.7 mi) wide shelf at less than 200 metres (660 ft) depth. ^[12] The shelf broadens with depth to form a large submarine volcano, which reaches a width of 57 kilometres (35 mi) at 2,500 metres (8,200 ft) depth. The total volume of Visokoi complete with the submarine parts is about 3,000 cubic kilometres (720 cu mi). ^[19] The submarine edifice has an east-west extension, with numerous small volcanoes, chutes ^[20] and traces (hummocky terrain) of a sector collapse ^[21] on the western side and a more extensive shelf cut by submarine canyons on the eastern side. From there, a submarine ridge connects Visokoi with Candlemas Island farther south. ^[20]

Geology

East of the South Sandwich Islands, the South America Plate subducts beneath the Scotia Plate at a rate of 70 millimetres per year (2.8 in/year). The subduction is responsible for the existence of the South Sandwich island arc, which is constituted by about eleven islands ^[4] in an eastward curving chain, ^[22] and submarine volcanoes such as Protector in the north and Adventure and Kemp in the south. ^[23] From north to south Zavodovski, Leskov Island, Visokoi Island, Candlemas Island-Vindication Island, Saunders Island, Montagu Island, Bristol Island-Freezland Rock, Bellingshausen Island, Cook Island-Thule Island emerge from the sea. Most of the islands are stratovolcanoes of various sizes. ^[24]

Composition

Volcanic rocks are mostly basaltic, but basaltic andesite and andesite are also found. ^[25] Phenocrysts include clinopyroxene, hypersthene, magnetite, olivine and plagioclase. ^[8] The rocks are notably iron-rich ^[26] and define a tholeiitic suite. ^[27]

Geologic history

The island grew during the past one million years by an alternation of pyroclastic rocks ^[8] and lava flows with columnar jointing, ^[28] cut by dykes, ^[29] building one volcano. ^[30] Later the eastern cinder cones formed, and the western side of the island was subject to coastal erosion. ^[8] Potassium-argon dating has yielded an age of 300,000 ± 100,000 years for a rock at Sulphur Point, ^[31] but activity continued into the Holocene ^[1] and the Finger Point lava flow may be recent. ^[12] An 18,000 years old tephra layer in the Vostok ice core has been attributed to Visokoi. ^[32]

The occurrence of historical eruptions is uncertain. ^[12] Eruptions were recorded in 1830, 1927 and 1930 ^[33] when passing ships observed smoke columns. ^[10] There are no tephra layers embedded in ice ^[8] but scoria lying on ice may represent either recent activity or older eruptions whose products were covered by ice and then re-exposed. ^[16]

Fumarole

An active fumarole associated with the scoria cone at Finger Point was observed in 1930. In 1962 this fumarole was gone, but volcanically heated ground was reported from the same site in 1964. ^[33] Thermal anomalies are not visible from satellite images. ^[14] The fumarole was surrounded by a concentric area of algae, lichens and mosses. ^[34]

Flora and fauna

Away from the fumarole, vegetation is largely absent from Visokoi ^[35] and consists mostly of lichens growing on bare rocks. ^[33] Non-vertebrates include mites and springtails ^[30] while amphipods, ^[36] brittle stars, bryozoans, sponges ^[37] and hydrozoans have been recovered from the shallow water surrounding Visokoi. ^[38]

Antarctic fulmars, cape petrels, chinstrap penguins, gentoo penguins, kelp gulls, macaroni penguins and skuas nest in the cliffs which are ice-free, and on the low coastal platforms especially at Finger Point. ^[33] More than 100,000 chinstrap penguin breeding pairs occur on Visokoi. ^[39] Additional seabirds and seals visit the island without clear evidence of reproduction. ^[40] Almost a thousand Antarctic fur seals were seen at Irving Point in 1964, making it the largest occurrence in the South Sandwich Islands. ^[41]

Human history

Visokoi was discovered on the 23 December 1819 by the Thaddeus von Bellingshausen expedition. ^[42] The proper spelling of the island name is Vysokij. ^[43] The island can be accessed from Wordie Point and Finger Point, where there are low-lying platforms. ^[8]

References

1. LeMasurier et al. 1990, p. 363.
2. Barr 2000, p. 318.
3. Lynch et al. 2016, p. 1615.
4. LeMasurier et al. 1990, p. 361.
5. Holdgate & Baker 1979, p. 22.
6. Barr 2000, p. 317.
7. Wild 1923, p. 84.
8. LeMasurier et al. 1990, p. 372.
9. Kargel et al. 2014, p. 773.
10. LeMasurier et al. 1990, p. 371.
11. Holdgate & Baker 1979, p. 23.
12. Leat et al. 2010, p. 117.
13. GVP 2023, General Information.
14. Patrick & Smellie 2013, p. 484.
15. Patrick & Smellie 2013, p. 483.
16. Holdgate & Baker 1979, p. 24.
17. Holdgate & Baker 1979, p. 26.
18. Holdgate & Baker 1979, p. 25.
19. Leat et al. 2010, p. 121.
20. Leat et al. 2010, p. 120.
21. Leat et al. 2010, p. 123.
22. Holdgate & Baker 1979, p. 3.
23. Leat et al. 2010, p. 111.
24. LeMasurier et al. 1990, p. 362.
25. Baker 1978, p. 9.
26. Baker 1978, p. 18.
27. Pearce et al. 1995, p. 1101.
28. GVP 2023, Photo Gallery.
29. Baker 1978, p. 6.
30. Baker et al. 1964, p. 693.
31. LeMasurier et al. 1990, p. 365.
32. コウノミカ,フジイヨシユキ 1999, p. 127.
33. Holdgate & Baker 1979, p. 27.
34. Longton & Holdgate 1979, p. 39.
35. Longton & Holdgate 1979, p. 40.
36. Alonso, Rauschert & de Broyer 2008, p. 23.
37. Fratt & Dearborn 1984, p. 130.
38. Cantero & Vervoort 2004, p. 808.
39. Hart & Convey 2018, p. 27.
40. Holdgate & Baker 1979, pp. 27–28.
41. Holdgate & Baker 1979, p. 28.
42. Holdgate & Baker 1979, p. 5.
43. Bulkeley 2021, p. 235.

Sources

• コウノミカ,フジイヨシユキ, Mika (1999). "Major element analysis of fine tephras found in an ice core from Dome Fuji Station, Antarctica". Polar Meteorology and Glaciology. 13: 123–132. doi:10.15094/00002896.
• Alonso, Gloria Maria; Rauschert, Martin; de Broyer, Claude (April 2008). "A catalogue of the Antarctic and sub-Antarctic Phoxocephalidae (Crustacea: Amphipoda: Gammaridea) with taxonomic, distribution and ecological data". Magnolia. 1752: 1. doi:10.11646/zootaxa.1752.1.1. hdl: 11336/135292 . ISSN   1175-5326.
• Baker, P. E.; Holdgate, M. W.; Longton, R. E.; Tilbrook, P. J.; Tomblin, J. F.; Vaughan, R. W.; Wynne-Edwards, C. J. C. (August 1964). "A Survey of the South Sandwich Islands". Nature. 203 (4946): 691–693. Bibcode:1964Natur.203..691B. doi:10.1038/203691a0. ISSN   1476-4687. S2CID   33809071.
• Baker, P.E. (1978). "The South Sandwich Islands: III. Petrology of the volcanic rocks" (PDF). British Antarctic Survey Scientific Reports. 93. Cambridge: British Antarctic Survey: 34.
• Barr, William (October 2000). "First landings on Zavodovski Island, South Sandwich Islands, 1819". Polar Record. 36 (199): 317–322. doi:10.1017/S0032247400016806. ISSN   1475-3057. S2CID   130347679.
• Bulkeley, Rip (2021). The Historiography of the First Russian Antarctic Expedition, 1819–21. Cham: Springer International Publishing. doi:10.1007/978-3-030-59546-3. ISBN   978-3-030-59545-6. S2CID   243441677.
• Cantero, A. L. Peña; Vervoort, W. (April 2004). "Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species". Journal of Natural History. 38 (7): 805–861. doi:10.1080/0022293021000045154. S2CID   84248772.
• Fratt, D. B.; Dearborn, J. H. (1 August 1984). "Feeding biology of the Antarctic brittle star Ophionotus victoriae (Echinodermata: Ophiuroidea)". Polar Biology. 3 (3): 127–139. doi:10.1007/BF00442644. ISSN   1432-2056. S2CID   45488834.
• "Hodson". Global Volcanism Program . Smithsonian Institution . Retrieved 22 September 2023.
• Hart, Tom; Convey, Peter (18 June 2018). "The South Sandwich Islands – a community of meta-populations across all trophic levels". Biodiversity: 1–14. doi:10.1080/14888386.2018.1464952. S2CID   133771224.
• Holdgate, M.W.; Baker, P.E. (1979). "The South Sandwich Islands: I. General description" (PDF). British Antarctic Survey Scientific Reports. 91. Cambridge: British Antarctic Survey: 76.
• Kargel, Jeffrey S.; Leonard, Gregory J.; Bishop, Michael P.; Kääb, Andreas; Raup, Bruce H., eds. (2014). Global Land Ice Measurements from Space. Berlin, Heidelberg: Springer Berlin Heidelberg. doi:10.1007/978-3-540-79818-7. hdl:2060/20040111284. ISBN   978-3-540-79817-0. S2CID   126510624.
• Leat, Philip T.; Tate, Alex J.; Tappin, David R.; Day, Simon J.; Owen, Matthew J. (September 2010). "Growth and mass wasting of volcanic centers in the northern South Sandwich arc, South Atlantic, revealed by new multibeam mapping". Marine Geology. 275 (1–4): 110–126. Bibcode:2010MGeol.275..110L. doi:10.1016/j.margeo.2010.05.001.
• 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. Washington, D. C.: American Geophysical Union. doi:10.1029/ar048. ISBN   978-0-87590-172-5.
• Longton, R.E.; Holdgate, M.W. (1979). "The South Sandwich Islands: IV. Botany" (PDF). British Antarctic Survey Scientific Reports. 94. Cambridge: British Antarctic Survey: 53.
• Lynch, Heather J.; White, Richard; Naveen, Ron; Black, Andy; Meixler, Marcia S.; Fagan, William F. (1 September 2016). "In stark contrast to widespread declines along the Scotia Arc, a survey of the South Sandwich Islands finds a robust seabird community". Polar Biology. 39 (9): 1615–1625. Bibcode:2016PoBio..39.1615L. doi:10.1007/s00300-015-1886-6. ISSN   1432-2056. S2CID   253814987.
• Patrick, Matthew R.; Smellie, John L. (August 2013). "Synthesis A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000–10". Antarctic Science. 25 (4): 475–500. Bibcode:2013AntSc..25..475P. doi:10.1017/S0954102013000436. ISSN   0954-1020. S2CID   128905897.
• Pearce, J. A.; Baker, P. E.; Harvey, P. K.; Luff, I. W. (1 August 1995). "Geochemical Evidence for Subduction Fluxes, Mantle Melting and Fractional Crystallization Beneath the South Sandwich Island Arc". Journal of Petrology. 36 (4): 1073–1109. doi:10.1093/petrology/36.4.1073.
• Wild, Frank (February 1923). "The Voyage of the "Quest"". The Geographical Journal. 61 (2): 73–97. doi:10.2307/1781104. JSTOR   1781104.

External links

• Hogg, Oliver T.; Downie, Anna-Leena; Vieira, Rui P.; Darby, Chris (2021). "Macrobenthic Assessment of the South Sandwich Islands Reveals a Biogeographically Distinct Polar Archipelago". Frontiers in Marine Science. 8. doi: 10.3389/fmars.2021.650241 . ISSN   2296-7745.