President Thiers Bank

President Thiers Bank is a broad[2] guyot,[3] which lies northwest of Rapa[4] and 200 kilometres (120 mi) southeast of Raivavae,[5] in the Austral Islands.[4] Its summit reaches a depth of 33 metres (108 ft).[6] It may have been created by the Macdonald hotspot.[7] Another theory sees in the seamount the endpoint of an alignment that starts with Aitutaki[8] and also involves one volcanic phase at Raivavae.[5]

President Thiers Bank
Summit depth33 metres (108 ft)
Location
Coordinates24°40′S 145°55′W / 24.667°S 145.917°W[1]Coordinates: 24°40′S 145°55′W / 24.667°S 145.917°W[1]
Geology
TypeGuyot

References

  1. ^ Adam, C.; Bonneville, A. (18 October 2008). "No thinning of the lithosphere beneath northern part of the Cook-Austral volcanic chains" (PDF). Journal of Geophysical Research. 113 (B10): 12. doi:10.1029/2007JB005313.
  2. ^ Menard, H. W.; McNutt, Marcia (1982). "Evidence for and consequences of thermal rejuvenation". Journal of Geophysical Research. 87 (B10): 8573. doi:10.1029/JB087iB10p08570.
  3. ^ Bonneville, Alain; Suavé, Raymond Le; Audin, Laurence; Clouard, Valérie; Dosso, Laure; Gillot, Pierre Yves; Janney, Philip; Jordahl, Kelsey; Maamaatuaiahutapu, Keitapu (1 November 2002). "Arago Seamount: The missing hotspot found in the Austral Islands". Geology. 30 (11): 1025. doi:10.1130/0091-7613(2002)030<1023:ASTMHF>2.0.CO;2. ISSN 0091-7613.
  4. ^ a b Maury et al. 2013, p. 559.
  5. ^ a b Maury et al. 2013, p. 565.
  6. ^ Fairbridge, Rhodes W.; Chevalier, J.-P. (1975). World Regional Geology. Springer, Berlin, Heidelberg. pp. 499–500. doi:10.1007/3-540-31081-1_111. ISBN 978-3-540-31081-5.
  7. ^ Johnson, Rockne H.; Malahoff, Alexander (10 May 1971). "Relation of Macdonald Volcano to migration of volcanism along the Austral Chain". Journal of Geophysical Research. 76 (14): 3289. doi:10.1029/JB076i014p03282.
  8. ^ Maury et al. 2013, p. 558.

Sources

  • Maury, R. C.; Guille, G.; Guillou, H.; Chauvel, C.; Rossi, P.; Pallares, C.; Legendre, C. (1 November 2013). "Temporal evolution of a Polynesian hotspot: New evidence from Raivavae (Austral islands, South Pacific ocean)". Bulletin de la Société Géologique de France. 184 (6): 557–567. doi:10.2113/gssgfbull.184.6.557. ISSN 0037-9409.
Arago hotspot

Arago hotspot is a hotspot in the Pacific Ocean, presently located below the Arago seamount close to the island of Rurutu, French Polynesia.

Arago is part of a family of hotspots in the southern Pacific, which include the Society hotspot and the Macdonald hotspot among others. These are structures beneath Earth's crust which generate volcanoes and which are in part formed by mantle plumes, although Arago itself might have a shallower origin. As the Pacific plate moves over the hotspots, new volcanoes form and old volcanoes are carried away; sometimes an older volcano is carried over the hotspot and is then uplifted as happened with Rurutu.

The Arago hotspot is responsible for the formation of Arago seamount and uplift on Rurutu; however reconstructions of the past positions of tectonic plates and geochemistry suggest that other islands and seamounts were constructed by the Arago hotspot during the past 120 million years. These potentially include Tuvalu, Gilbert Islands, the Ratak Chain of the Marshall Islands as well as part of the Austral Islands and Cook Islands.

Foundation Seamounts

Foundation Seamounts are a series of seamounts in the southern Pacific Ocean. Discovered in 1992, these seamounts form a 1,350 kilometres (840 mi) long chain which starts from the Pacific-Antarctic Ridge. Some of these seamounts may have once emerged from the ocean.

The Foundation Seamounts were probably formed by a now-weakening mantle plume called the Foundation hotspot that is located close to the Pacific-Antarctic Ridge. It is possible that this hotspot generated additional volcanoes, such as the Ngatemato and Taukina seamounts farther west. The oldest volcanism on the Foundation Seamounts occurred 21 million years ago, while the youngest volcanism appears to be hydrothermal venting and the eruption of a lava flow between 1997-2001 where the Foundation Seamounts intersect the Pacific-Antarctic Ridge.

Hotspot (geology)

In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.

Macdonald seamount

Macdonald seamount (named after Gordon A. MacDonald) is a seamount in Polynesia, southeast of the Austral Islands and in the neighbourhood of a system of seamounts that include the Ngatemato seamounts and the Taukina seamount. It rises 4,200 metres (13,800 ft) from the seafloor to a depth of about 40 metres (130 ft) and has a flat top, but the height of its top appears to vary with volcanic activity. There are some subsidiary cones such as Macdocald seamount. The seamount was discovered in 1967 and has been periodically active with gas release and seismic activity since then. There is hydrothermal activity on Macdonald, and the vents are populated by hyperthermophilic bacteria.

Macdonald seamount is the currently active volcano of the Macdonald hotspot, a volcanic hotspot that has formed this seamount and some other volcanoes. Eruptions occurred in 1967, 1977, 1979–1983 and 1987–1989, and earthquakes were recorded in 2007. The activity, which has produced basaltic rocks, has modified the shape of the volcano and may lead to the formation of an island in the future.

Outline of oceanography

The following outline is provided as an overview of and introduction to Oceanography.

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