Английская Википедия:Candlemas Island

Шаблон:Short description Шаблон:Use dmy dates Шаблон:Infobox islands Candlemas Island is a small uninhabited island of the Candlemas Islands in the South Sandwich Islands. It is one of about a dozen islands that make up the South Sandwich island arc, a chain of volcanoes in the Southern Ocean that was discovered in 1775 by James Cook. The volcanism is caused by the subduction of the South American Plate beneath the Sandwich Plate. The island is remote and rarely visited due to the often hostile weather conditions, but is populated by penguins and seabirds, which form large breeding colonies.

The island consists of two parts. The southeastern part is older and consists of the heavily glaciated volcanoes Mount Andromeda - with Шаблон:Convert elevation the highest point of the island - and Mount Perseus, and shows no evidence of recent activity. The northwestern part features the younger scoria cone complex Lucifer Hill, which is surrounded by lava flows. Some of the lava flows may have been emplaced during the 20th century. The older rocks consist mostly of basalt and basaltic andesite, while the younger rocks are predominantly andesite and dacite; the two groups share a common magma formation process.

The Lucifer Hill complex features numerous fumaroles which emit volcanic gases. A vegetation community consisting of mosses and lichens grows around the fumaroles, with some members extending to non-fumarolic terrain.

Geography and geomorphology

Candlemas Island is one of the South Sandwich Islands, a Шаблон:Convert long north–south trending island arc to the southeast of South Georgia and the Falklands. They include Zavodovski, Leskov Island, Visokoi, Candlemas and Vindication Island, Saunders Island, Montagu Island, Bristol Island and Freezland Rock, Bellingshausen Island, Cook Island and Thule Island. All the islands are small and volcanic, most showing evidence of activity during the last two centuries.Шаблон:Sfn They are subject to intense marine erosion. Submarine volcanoes including Protector Shoals at the northern and Nelson and Kemp seamounts at the southern end of the island chain.Шаблон:Sfn

The island is also known as Lichtmess-Insel and Candelaria.Шаблон:Sfn It is rarely visitedШаблон:Sfn owing to the hostile weather and sea conditions,Шаблон:Sfn and the south and southeast coasts are hardly accessible;Шаблон:Sfn tourist vessels occasionally land on Candlemas.Шаблон:Sfn Longline fishing takes place in the surrounding waters.Шаблон:Sfn Politically, South Georgia and the South Sandwich Islands make up the UK Overseas Territory of South Georgia and the South Sandwich Islands. In 2012, a marine protected area was established in the South Sandwich Islands. The scope of the protected area was further expanded in 2019.Шаблон:Sfn

With dimensions of Шаблон:Convert,Шаблон:Sfn Candlemas is the third-largest of the South Sandwich IslandsШаблон:Sfn and consists of a southeastern, roughly square-shaped half and an irregularly shaped northwestern half.Шаблон:Sfn Vindication Island to the west is separated from Candlemas by the shallow (Шаблон:Convert Шаблон:Sfn-Шаблон:Convert) Шаблон:Convert wide Nelson Channel. Visokoi lies Шаблон:Convert north and Saunders Шаблон:Convert south of Candlemas Island.Шаблон:Sfn

The northwestern half consists of a complex of scoria cones named Lucifer Hill (also known as Lucifer HillsШаблон:Sfn),Шаблон:Sfn which reach a maximum elevation of Шаблон:Convert,Шаблон:Sfn Шаблон:Convert Шаблон:Sfn or Шаблон:Convert above sea level.Шаблон:Sfn Two main craters with depths of about Шаблон:Convert and diameters of Шаблон:Convert flank the main summit, which has a flat top. A subsidiary crater lies on the southwestern flank.Шаблон:Sfn They are surrounded by five lava flows, the eastern of which is old and covered with volcanic ash Шаблон:Sfn while the northern one is younger, with an irregular surface featuring blocks, ridges and gullies.Шаблон:Sfn The lava flows are morphologically aa lavas.Шаблон:Sfn The eastern lava flow forms Breakbones Plateau, while a northwestward extending lava flow constitutes the Vulcan Point peninsula. The southwestward and northwestward extending lava flows enclose the Tow Bay; Cauldron Pool lies just east of Tow Bay.Шаблон:Sfn Another unnamed pool lies at the end of Clinker Gulch on Lucifer Hill,Шаблон:Sfn and there are freshwater pools throughout the island.Шаблон:Sfn The coastline is formed by cliffs with interspersed recesses and bays.Шаблон:Sfn

The southeastern half is the larger and consists of an extinctШаблон:Sfn and eroded stratovolcano.Шаблон:Sfn A north-south trending ridgeШаблон:Sfn has two summits, the northeastern Шаблон:Convert high Mount PerseusШаблон:Sfn and the southeastern Mount Andromeda; the latter is the highest point of Candlemas with Шаблон:Convert Шаблон:Sfn or Шаблон:Convert elevation.Шаблон:Sfn This half is asymmetric, rising from west to east, which may indicate that it is the remnant of a formerly larger volcano that was centered east of the current island.Шаблон:Sfn Glaciers coverШаблон:Sfn most of the southeastern half of Candlemas,Шаблон:Sfn an area of Шаблон:Convert Шаблон:As of Шаблон:Sfn which amounts to 40% of the island.Шаблон:Sfn The ice reaches thicknesses of Шаблон:Convert in coastal cliff exposures.Шаблон:Sfn On the southern and eastern side of Candlemas, the ice descends to the sea, in the northШаблон:Sfn it forms glacer tongues at elevations of Шаблон:Convert Шаблон:Sfn surrounded by a belt of moraines around the ice edge.Шаблон:Sfn Streams draining meltwater Шаблон:Sfn have incised glacial deposits.Шаблон:Sfn Cliffs with heights of Шаблон:Convert form most of the southern and eastern coasts,Шаблон:Sfn while a Шаблон:Convert wide youthful coastal terrace makes up the western and northern side.Шаблон:Sfn Marine deposits have formed the northward extending Demon Point peninsula, which encloses Kraken Bay between the peninsula and Lucifer Hill. Shrove Point is the southeastern end of Candlemas Island, while Boot Rock juts out from the eastern coastline and ClapmatchШаблон:Sfn and Carbon Points.Шаблон:Sfn Шаблон:Convert east of the coastline is the islet Tomblin Point.Шаблон:Sfn

Between the two halves lies Chimaera Flats,Шаблон:Sfn a southwest–northeast trending sandy plainШаблон:Sfn with two lagoons named Gorgon Pool and Medusa Pool.Шаблон:Sfn Medusa Pool is the southwestern lagoon and was connected to the sea at Sea Serpent Cove in 1964, while Gorgon Pool is the northeastern one.Шаблон:Sfn The configuration of Chimaera Flats is variable over time, during 1830-1927 Candlemas Island was sometimes reported to consist of three islandsШаблон:Sfn although visual conditions can lead to Candlemas Island being mistaken for two islands.Шаблон:Sfn The two halves of Candlemas Island shielded the terrain from marine erosion,Шаблон:Sfn thus allowing the growth of spits formed by boulders and shingles.Шаблон:Sfn

Submarine structure

Both Candlemas and Vindication rise from the same submarine volcano, and are named the Candlemas Islands.Шаблон:Sfn Around the islands the sea is less than Шаблон:Convert deep,Шаблон:Sfn forming a Шаблон:Convert wide shallow platform with numerous shoals, islets and sea stacks.Шаблон:Sfn They are remnants of eroded islandsШаблон:Sfn and include Buddha Rock, Castor Rock, Cook Rock, Pollux Rock, Santa Rock, Saw Rock, Tomblin Rock and Trousers Rock. Most of the islets lie around Vindication.Шаблон:Sfn Шаблон:Sfn Some of these rocks make up a series of shoals between the islands.Шаблон:Sfn The shelf itself probably formed through marine erosion and scouring by icebergs.Шаблон:Sfn

The volcano has a base diameter of more than Шаблон:Convert at Шаблон:Convert Шаблон:Sfn and a total volume of about Шаблон:Convert.Шаблон:Sfn Away from the shallow platform, the slopes of the volcano drop off steeply into the deep ocean.Шаблон:Sfn East of Candlemas and abutting its southeastern side is a large Шаблон:Convert wide submarine embayment, probably the remnant of a large sector collapse.Шаблон:Sfn Two other structures interpreted as landslide scars lie north and south of the shelf,Шаблон:Sfn which is scalloped by landslide scars.Шаблон:Sfn The submarine slopes have wave-like bedforms in many places.Шаблон:Sfn Smaller ridges emanate from the submarine volcano and are interpreted as parts of it,Шаблон:Sfn while chutes emanating in all directions formed through mass wasting.Шаблон:Sfn A submarine ridge at Шаблон:Convert depth connects the group to Visokoi farther north.Шаблон:Sfn West of Candlemas, monogenetic volcanoes are developed on the seafloor.Шаблон:Sfn

Geology

East of the South Sandwich Islands, the South America Plate subducts into theШаблон:Sfn more than Шаблон:Convert deep South Sandwich TrenchШаблон:Sfn at a rate of Шаблон:Convert.Шаблон:Sfn The volcanic arc consists of volcanoes with heights of Шаблон:Convert that developed on top of the Sandwich Plate,Шаблон:Sfn which is produced at the East Scotia Ridge west of the arc.Шаблон:Sfn Both the underlying oceanic crust (8-10 million years old) and the volcanic arc appear to be young; this may explain the peculiar basalt-rich composition and small size of the volcanoes.Шаблон:Sfn

Composition

Volcanic rocks from Candlemas consist of basalt, basaltic andesite,Шаблон:Sfn andesite and dacite.Шаблон:Sfn The basalts and basaltic andesite define a potassium-poor tholeiitic suite,Шаблон:Sfn while the andesites and dacites are calc-alkaline. Phenocrysts include feldspar, olivine, plagioclase and pyroxene,Шаблон:Sfn and there are gabbro-like xenoliths,Шаблон:Sfn but unlike other South Sandwich volcanoes the lavas are mostly aphyric.Шаблон:Sfn Rocks from the older southeastern half are mostly basaltic, the younger northwestern half is mostly andesitic/Шаблон:Sfn dacitic,Шаблон:Sfn one dacitic obsidian has been reported from the southeastern half.Шаблон:Sfn Some rocks have been weathered.Шаблон:Sfn Sulfur has accumulated around active fumaroles.Шаблон:Sfn

The basalt, which forms about 90% of all Candlemas rocks, is considered to be the primary rock,Шаблон:Sfn from which the andesites evolved through fractional crystallization.Шаблон:Sfn A contribution of melting slab rocks is likely.Шаблон:Sfn The rocks of southeastern Candlemas resemble these of Vindication.Шаблон:Sfn

Eruption history

No radiometric dating has been performed on Candlemas Island rocks,Шаблон:Sfn but the island appears to have formed in two stages. During the first stage, the southeastern half of the island formed, which today constitutes about 90% of the volume of Candlemas.Шаблон:Sfn Outcrops in cliffs of the southeastern half of the island feature alternating layers of porphyritic lava flows and scoria, which are intruded by dykes and sills and show evidence of later deformation.Шаблон:Sfn Apart from the lava flows, some deposits were originally emplaced in now-dry lagoons, others formed through fallout.Шаблон:Sfn Subglacial eruptions of Mount Perseus produced glacial meltwater floods.Шаблон:Sfn Close to Medusa Pool, some lava flows have become palagonitic. Later in the history of the island, two lava flows were emplaced on the southwestern end of the southeastern half of Candlemas; they form Carbon Point and Clapmatch Point.Шаблон:Sfn Шаблон:Sfn These flows may be analogous to historical eruptions at Tristan da Cunha.Шаблон:Sfn The southeastern half of the island was extensively eroded by the sea and by glaciers.Шаблон:Sfn

After a hiatus, volcanism shifted north of the previous volcanic centre, where eruptions in shallow water formed Lucifer HillШаблон:Sfn initially probably as a separate island.Шаблон:Sfn It is possible that an earlier volcano existed at the present location of Lucifer Hill, leaving pyroclastic flow deposits in the northwestern sector of the southeastern half of Candlemas Island.Шаблон:Sfn Lucifer Hill consists mostly of volcanic ash mixed with scoria, with blocks reaching sizes of Шаблон:Convert.Шаблон:Sfn The oldest outcrops belong to the northern cone and are found in Clinker Gulch. The cones emitted numerous lava flows reaching thicknesses of Шаблон:Convert, separated by scoria and ash eruptions.Шаблон:Sfn Lava flows are thick and fragmented, with surface ridges.Шаблон:Sfn The relative ages of the lava flows have been established from their appearance and relative grade of erosion;Шаблон:Sfn two southern and northern flows formed first. Then the entire eastern half of the lava flow field was emplaced. Subsequently, the southwestern lava flow was erupted from the southern vent. Last, the northwestern lava flow and lava flows on the southeastern flank were emplaced.Шаблон:Sfn The lava flows form Шаблон:Convert wide lava deltas.Шаблон:Sfn

Chronology and historical reports

Unlike the first stage, which may have lasted for 1-2 million years, the second stage probably only began a few centuriesШаблон:Sfn or millennia ago, which might make it one of the youngest volcanoes of the South Sandwich Islands.Шаблон:Sfn There is no evidence of recent activity in the southeastern half of the island,Шаблон:Sfn other than a localized tilting in its northwestern sector that may be caused by the activity of northwestern Candlemas.Шаблон:Sfn

The ice of Mount Andromeda contains tephra layers produced by eruptions of Lucifer Hill.Шаблон:Sfn A 6,000 years oldШаблон:Sfn tephra layer in the Vostok and South Pole ice cores has been tentatively attributed to a large explosive eruption at Candlemas,Шаблон:Sfn which would have spread ash over a distance of Шаблон:Convert.Шаблон:Sfn Research published in 2001 indicated that this tephra may have originated at a different South Sandwich Islands volcano.Шаблон:Sfn The Global Volcanism Program cites a 1250 BCE eruption recorded in ice cores, most likely from Candlemas.Шаблон:Sfn Three other tephra layers in the Vostok ice core, dated to 30,000, 36,500 and 109,500 years ago may have originated at Candlemas.Шаблон:Sfn

Owing to their remote location, volcanic activity in the South Sandwich Islands is poorly documented.Шаблон:Sfn Шаблон:Sfn No eruptions have been directly observed at Candlemas.Шаблон:Sfn Steam and dark clouds were reported in 1823 and 1911.Шаблон:Sfn Some discrepancies between maps may indicate activity since 1930.Шаблон:Sfn Glowing lava fields were observed from the Шаблон:Ship in 1953–1954 on the northern side of Candlemas,Шаблон:Sfn and steam emission indicates that the northern lava flow may have been emplaced during this eruption,Шаблон:Sfn but it is not clear which lava flow,Шаблон:Sfn and the 1953-1954 report was considered questionable by LeMasurier et al. 1990.Шаблон:Sfn Volcanic tremors were recorded in 1998.Шаблон:Sfn

Fumaroles

Lucifer Hill is fumarolically active,Шаблон:Sfn emitting steam and sulfurous gases. Gas emissions are concentrated in its two craters and at various fumaroles on its lower slopes.Шаблон:Sfn The fumarolic activity can be seen from passing ships.Шаблон:Sfn One fumarole in 2020Шаблон:Sfn had a temperature of Шаблон:Convert.Шаблон:Sfn Carbon dioxide is the principal non-water gas emitted by the fumaroles; sulfur species are dominated by hydrogen sulfide.Шаблон:Sfn Temperatures underground reach Шаблон:Convert at Шаблон:Convert depth;Шаблон:Sfn the volcanic warmth keeps Lucifer Hill ice-freeШаблон:Sfn Шаблон:Sfn and the lack of ice/Шаблон:Sfn heat signature has been observed from space by satellites.Шаблон:Sfn The southeastern half of Candlemas lacks fumarolic activity.Шаблон:Sfn

Vent locations change over time,Шаблон:Sfn with a survey in 1997 noting a decline of fumarolic activity and vegetation shifts associated with changes in the fumarolic vents.Шаблон:Sfn In 1962, a geyser was observed at Cauldron Pool; in 1964 the geyser was gone but water temperatures in the pool exceeded Шаблон:Convert in many locations,Шаблон:Sfn with the pool itself steaming.Шаблон:Sfn In 1997 the hot pools were gone as well but Шаблон:As of Cauldron Pool does not freeze over.Шаблон:Sfn

Climate

The South Sandwich Islands have an oceanic climate with sparse sunshine, low seasonal temperature variation and temperatures only a few degrees above freezing most of the year.Шаблон:Sfn The skies on Candlemas Island are usually overcast, and strong westerly winds blow. The winds mobilize glacial dust and volcanic deposits.Шаблон:Sfn Fog is common.Шаблон:Sfn Between June and November the sea surrounding the islands is covered with sea ice.Шаблон:Sfn Icebergs occur around Candlemas and occasionally run aground in shallow waters.Шаблон:Sfn

Life

Plant communities consisting of hepatics, liverworts and mosses grow around fumaroles Шаблон:Sfn with a distinct structuration that can extend to Шаблон:Convert width.Шаблон:Sfn Fumaroles provide water through condensation of steam, supporting life.Шаблон:Sfn Similar but less well-developed communities grow on cold terrain, where various forms of lichens predominate.Шаблон:Sfn Plant cover is most widespread on Breakbones Plateau and at the edge of the ice cap.Шаблон:Sfn The ground temperatures where mosses grow range between Шаблон:Convert and Шаблон:Convert.Шаблон:Sfn Dead plants have accumulated to form peat, in some places reaching thicknesses of Шаблон:Convert.Шаблон:Sfn Algae grow inside of fumarolic vents,Шаблон:Sfn in ice Шаблон:Sfn and in bird colonies.Шаблон:Sfn Basidiomycetes fungi grow among the plants,Шаблон:Sfn and other fungi cause white bands in the vegetation, killing it.Шаблон:Sfn One higher plant, the Antarctic hair grass, has been reported from fumarolic terrainШаблон:Sfn and its occurrence is restricted to these.Шаблон:Sfn

The vegetation resembles that of Deception Island, another volcanic island around Antarctica.Шаблон:Sfn The low temperatures and the high permeability of the ground restrict vegetation growth on most of the South Sandwich Islands,Шаблон:Sfn and trampling and faecal input from penguin colonies further limit growth close to penguin colonies.Шаблон:Sfn There are no known introduced species.Шаблон:Sfn

Seabirds are abundant at Candlemas.Шаблон:Sfn Penguins, petrels and skuas visit the island,Шаблон:Sfn and there are penguin colonies at numerous sites along the coast.Шаблон:Sfn Large breeding populations with over a hundred members have been recorded for Adélie penguins, brown skuas, cape petrels, chinstrap penguins, gentoo penguins, macaroni penguins, snow petrels, southern fulmars, southern giant petrels (their main breeding site in the South Sandwich IslandsШаблон:Sfn). Other birds that breed on Candlemas are Wilson's storm petrels and black-bellied storm petrels.Шаблон:Sfn Шаблон:Sfn Mammals include Antarctic fur seals, elephant seals, leopard seals and Weddell seals,Шаблон:Sfn which reproduce on the island.Шаблон:Sfn Penguin populations appear to be stable on Candlemas Island.Шаблон:Sfn Finds of charred bones imply that penguin populations are sometimes impacted by volcanic activity.Шаблон:Sfn Small animals include mites, nematodes, rotifers, springtails and tardigrades.Шаблон:Sfn Шаблон:Sfn Ticks have been recovered from birds.Шаблон:Sfn Amphipods,Шаблон:Sfn brittle stars Шаблон:Sfn and echinoderms occur on the shelf around Candlemas Island,Шаблон:Sfn Шаблон:Sfn and sea pens from somewhat deeper waters.Шаблон:Sfn

New species

The bacterium Bacillus fumarioli was discovered in soils on Candlemas Island, Mount Melbourne and Mount Rittmann.Шаблон:Sfn This wide dispersion may indicate that it is propagated by wind.Шаблон:Sfn Other species that were originally discovered on Candlemas Island are Bacillus shackletonii, which grew in soils on lava flowsШаблон:Sfn and was later renamed Heyndrickxia shackletonii,Шаблон:Sfn Bacillus luciferensis, which was discovered in soils from Lucifer Hill and named after the site of discovery,Шаблон:Sfn Paenibacillus cineris and Paenibacillus cooki,Шаблон:Sfn both from soil around an active fumarole.Шаблон:Sfn The mite Calvolia antarctica was discovered in lichen-encrusted rocks of Candlemas Island.Шаблон:Sfn

Research history

Candlemas Island was discovered on 2 February 1775Шаблон:Sfn (Candlemas Day, hence the nameШаблон:Sfn) by James Cook from the Шаблон:Ship, but he did not visit it. In the 19th century, only sealers went to Candlemas, and whaling took place in the surrounding sea. During the 20th century scientific research and landings began, first C.A. Larsen in 1908 landed on Shrove Point at the southeastern end of Candlemas, then by the Шаблон:Ship in January 1961 and the ice patrol ship Шаблон:Ship in March 1962 and 1964. As a consequence of the 1964 visit, Candlemas Island is the best investigated of the South Sandwich Islands.Шаблон:Sfn Шаблон:Sfn Some of these investigations established temporary field camps on Candlemas Island.Шаблон:Sfn Sealing and whaling activities are largely undocumented,Шаблон:Sfn but archaeological evidence indicates that landing parties stayed on Candlemas for several weeks,Шаблон:Sfn and sealing activity may have led to the disappearance of Antarctic fur seals from the surroundings.Шаблон:Sfn

Other

Marine debris, mostly human in origin, has been found at Candlemas Island.Шаблон:Sfn

References

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Sources

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External links

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