The Pleiades are avolcanic group in northernVictoria Land ofAntarctica. It consists of youthfulcones anddomes with Mount Atlas/Mount Pleiones, a smallstratovolcano formed by three overlapping cones, being the dominant volcano and rising 500 m (1,600 ft) above theEvans Névé plateau. Two other named cones are Alcyone Cone and Taygete Cone, the latter of which has beenradiometrically dated to have erupted during theHolocene. A number oftephra layers across Antarctica have been attributed to eruptions of this volcanic group, including several that may have occurred within the last few hundred years.
The volcanic group is formed by at least 12[9] steep,[10] small volcanic cones andlava domes thatemerge from the ice of Evans Neve[11] over a 13 km (8.1 mi) long area. Most are nameless with the exception of the central Taygete Cone, Alcyone Cone just south of Taygete and the pair ofc. 3,020 m (9,910 ft) high Mount Pleiones and c. 3,040 m (9,970 ft) high Mount Atlas in the southern sector.[12] Mount Atlas and Mount Pleiones form a compoundstratovolcano[13] which is the principal volcano of The Pleiades[3] and rises about 500 metres (1,600 ft) above the ice.[14] Mount Atlas is formed by three separate cones that rise 0.5 km (0.31 mi) above the ice.Dykes,lava andscoria flows are found on these cones, the youngest of which has a semicircular crater.[15] andscoria cones dot its flanks.[11] At the foot of Mount Atlas aremoraines with the form of ridges[15] and there are moraines within one of its craters as well.[16] The summit of Mount Pleiones features nested craters.[17] The distribution of the cones may mark the edges of a buriedcaldera.[18]
Alcyone Cone lies 3.5 km (2.2 mi) north of Mount Atlas.[5] It is only slightly lower than Mount Atlas but is much smaller. It has two poorly defined craters and consists of lava flows covered withscree andvolcanic bombs when not buried under snow.[15] Taygete Cone 6 km (3.7 mi) north of Mount Atlas[5] appears to be alava dome bearing traces ofhydrothermal alteration and of a small crater.[15] Apart from the lava flows which make up most of Mount Atlas,[19]pyroclastic rocks have been encountered at The Pleiades.[3] The other cones are partly buried by snow and some have breached or otherwise eroded craters.[20]
The volcanoes have alternatively been described as eroded[19] or uneroded.[3] The young appearance of the edifices indicates a young age of The Pleiades volcanoes.[3] The volcanoes have been prospected for the possibility to generategeothermal energy but the presence of a good heat source is unlikely.[21] An aeromagnetic anomaly has been correlated to the volcano group.[22] The cones form an arcuate alignment that might reflect the existence of a 6 kilometres (3.7 mi) wide caldera to their southeast.[23]
The Pleiades belong to theMcMurdo Volcanic Group and more specifically to the Melbourne volcanic province, which extends fromMount Melbourne to The Pleiades andMalta Plateau.[3] These consist of theCenozoic volcanoes of northernVictoria Land which form alignments and lineaments possibly controlled by deep fractures, and which are subdivided into a "Central Suite" consisting of largestratovolcanoes and a "Local Suite" consisting of other volcanic centres. Among the volcanoes of the McMurdo Volcanic Group are the large volcanoesMount Overlord,Mount Melbourne[4] and in the area of The Pleiades theMalta Plateau.[10] Volcanic activity began about 10 – 7 million years ago.[24] Earlier volcanic activity began during theCretaceous, when theWest Antarctic Rift System became active.[25]
Thecrust under the volcanic field is about 40 kilometres (25 mi) thick.[26] Thebasement underneath the volcanoes consists ofPrecambrian andPaleozoic sedimentary andintrusive rocks. The former are mostly represented by theBowers Group/Bowers Supergroup and theRobertson Bay Group north of the volcanic complex and the latter by theGranite Harbour andAdmiralty Intrusives mostly south of the volcanic complex. A major localfault system passes northeast of the volcanoes[6][27] and roughly follows the path of the Mariner Glacier,[27] while the Lanternman Fault passes southwest of them.[25] Some of these faults formed during theRoss Orogeny, when threeterranes collided to form northern Victoria Land;[28] The Pleiades are located on theBowers Terrane.[25] Faults may also govern the position of The Pleiades volcanoes.[29]
The oldest dated rocks are 847,000 ± 12,000 years old.[16] Eruptions took place about 825,000 years ago and emplaced trachytes in the central part of the field; even older eruptions may have occurred but are now buried underneath of snow and ice. Three more eruptions occurred in the subsequent 700,000 years before activity began to increase after 100,000 years.[35]potassium–argon dating has yielded imprecise ages of 40,000 ± 50,000 for Mount Atlas and 20,000 ± 40,000 and 12,000 ± 40,000 for other volcanic cones.[12] Laterargon-argon dating has yielded ages of less than 100,000 years for lavas on Mount Atlas[35] and for a lava east of Taygete, and ages of about 45,000 years for Alcyone and two more lava flows on Mount Atlas.[36] The Pleiones-Atlas complex may have last erupted 20,000 ± 7,000 years ago.[16] Volcanic activity may have been influenced by ice load, which prevented the ascent of the magmas and allowed them to accumulate and evolve in the crust,[37] yielding peculiar magmas that underwent intensecrystal fractionation and absorbed large quantities of crustal material.[38] When ice loads decreases, the evolved magmas rise to the surface.[39]
Tephra deposits have been found inAntarctica which may originate at The Pleiades. These include:
Tephras inice cores that date to 1776 – 1885 AD,[49] including one tephra layer atSiple Dome dated to about 1809.[50]
Finally, a major eruption may have occurred either at The Pleiades or at Mount Melbourne between 1880 and 1980.[51]
The youngest ages of 6,000 ± 6,000[36] and 3,000 ± 14,000 years ago have been obtained on Taygete,[12] which together with the youthful texture of this dome[13] indicates a young age for The Pleiades, despite the imprecise dates.[15] The presence ofpumicelapilli has been taken as evidence of very recent activity in the form of a moderate pumice eruption.[52] Presently, only minorfumarolic activity has been reported.[51] Future eruptions are possible[36] and The Pleiades are not monitored, but they are also remote from any research station.[53]
^abBoutron, Claude (20 December 1980). "Respective influence of global pollution and volcanic eruptions on the past variations of the trace metals content of Antarctic snows since 1880s".Journal of Geophysical Research: Oceans.85 (C12): 7431.Bibcode:1980JGR....85.7426B.doi:10.1029/JC085iC12p07426.
Rocchi, Irene; Tomassini, Alice; Masotta, Matteo; Petrelli, Maurizio; Ágreda López, Mónica; Rocchi, Sergio (1 April 2024). "Textures and Chemistry of Crystal Cargo of the Pleiades Volcanic Field, Antarctica: Potential Influence of Ice Load in Modulating the Plumbing System".Journal of Petrology.65 (4).doi:10.1093/petrology/egae027.
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