South Arch volcanic field

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Coordinates: 17°15′N 155°45′W / 17.250°N 155.750°W / 17.250; -155.750
Source: Wikipedia, the free encyclopedia.
South Arch volcanic field
Hawaiʻi Island
Highest point
Hawaiʻi Island
CountryUnited States
StateHawaii
Geology
Mountain typeVolcanic field
Type of rockBasaltic rock
Map
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200km
124miles
South Arch
Location south of the Hawaiian Islands

South Arch volcanic field is an

Hawaiʻi Island
. It was active during the last 10,000 years, and covers an area of 35 by 50 kilometres (22 mi × 31 mi) at a depth of 4,950 metres (16,240 ft).

Although the field is related to the Hawaiian hotspot, it does not appear to be a precursory volcano, but seems to have formed when the weight of the growing Hawaiian volcanoes caused the oceanic crust to buckle, opening up pathways for magma to ascend in front of the hotspot.

Geomorphology

The volcanic field lies about 200 kilometres (120 mi) south from

seamounts[2] mainly to the west and southwest.[1]

In sidescan sonar images, young lava flows have a bright appearance while older ones are covered by sediments and thus appear darker, and structures identified as lava coils, lava rubble, lava tumuli, pillow lavas, polygons and sheet flows have been observed on young flows. The lava flows have buried the pre-existent seafloor topography, smoothening it,[2] and in one place a flow front rises about 10 metres (33 ft) from the seafloor.[4] The lava flows erupted in the South Arch volcanic field were probably fluid and were produced at high rates.[5] There is no evidence for the presence of a magma chamber at the South Arch volcanic field.[6]

Geology

The volcanic field is located on the crest of the Hawaiian Arch, an area of Cretaceous seafloor around Hawaii which has buckled under the weight of the Hawaiian volcanoes, causing uplift and volcanic activity[1] where the crust has broken up, allowing magma to rise to the surface.[5] The presence of older seamounts in the area of the South Arch volcanic field may have influenced the onset of volcanism in the field.[5] Such eccentric volcanism has also been inferred at other hotspots.[7]

The South Arch volcanic field is not the only volcanic system on the Arch, there is also the

Hawaiian hotspot[10] and has been described as "precursory"[11] although it does not appear to be an early stage of a typical Hawaiian shield volcano.[3]

Composition

Dredging has yielded

clinopyroxene, iddingsite, olivine, plagioclase and sometimes spinel.[4] Lava flows are covered by manganese crusts less than 0.15 millimetres (0.0059 in) thick.[12] They often display traces of alteration and formation of glasses such as palagonite. Some dredge samples might come from neighbouring Cretaceous seamounts rather than the South Arch volcanic field, however.[4]

The alkalic composition

Hawaiian hotspot and components typical of mid-ocean ridge basalts may have given rise to the volcanics of the South Arch volcanic field,[15] with metasomatism involved as well.[16] The magmas of the South Arch volcanic field appear to have been unusually water-rich, perhaps because of an early melting of water-rich mantle.[17]

Eruption and research history

The field appears to consist of some central younger lava flows which are surrounded by older lava flow fields.

Kilauea and Kamaʻehuakanaloa rocks.[19] Another age range cited in the literature is 14,000–20,000 years ago.[20] It is possible that magma ascended to the surface mainly in areas where the lithosphere has anomalous properties and is more likely to crack rather than to flex; this would explain why the vents of the South Arch volcanic field coincide with Cretaceous seamounts.[21]

The South Arch volcanic field was discovered in 1986 through

GLORIA sidescan sonar imaging and dredged in 1988.[1] Another investigation by the Kaikō remotely operated underwater vehicle took place in 2001;[22] in general the field has been explored by dredging, remotely operated underwater vehicle and submersible.[12]

References

  1. ^ a b c d e f g h i j Holcomb et al. 1989, p. 611.
  2. ^ a b c d Holcomb et al. 1989, p. 612.
  3. ^
    doi:10.1016/j.epsl.2011.09.041
    .
  4. ^ a b c d Holcomb et al. 1989, p. 613.
  5. ^ a b c d e Holcomb et al. 1989, p. 614.
  6. doi:10.1130/G22077.1 – via ResearchGate
    .
  7. doi:10.2973/odp.proc.sr.129.128.1992
    .
  8. ISSN 0012-821X
    .
  9. ^ Clague et al. 1990, p. 184.
  10. ^ Clague & Dixon 2001, p. 629.
  11. ^ Clague & Dixon 2001, p. 640.
  12. ^ a b Clague & Moore 2004, p. 341.
  13. ^ Clague et al. 1990, p. 181.
  14. ISBN 9781118872161
    .
  15. Bibcode:2005AGUFM.V51A1470K
    .
  16. ^ Clague & Dixon 2001, p. 645.
  17. ^ Clague & Dixon 2001, p. 650.
  18. ^ Holcomb et al. 1989, pp. 613–614.
  19. ^ Clague & Moore 2004, p. 343.
  20. ISSN 0022-3530
    .
  21. ^ Clague et al. 1990, p. 190.
  22. doi:10.1016/j.chemgeo.2004.08.051
    .

Sources

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