Geology of the Cook Islands

Last updated
The hotspot highway intersects in the area of the Cook Islands. The tracks shown in this map are no longer fully accurate due to further definition. The Rarotonga track has indifferent evidence. HotspotHighway.jpg
The hotspot highway intersects in the area of the Cook Islands. The tracks shown in this map are no longer fully accurate due to further definition. The Rarotonga track has indifferent evidence.

There are fifteen Cook Islands, all being related to extinct volcanoes that have erupted in the volcanic hotspot highway of the south-central Pacific Ocean. Low islands include six of the more northern islands that are atolls, and four of the more southern being uplifted coral islands. Rarotonga, the largest island of the group is a mountainous volcanic island. Rock formations include late Pliocene to more recent volcanics, Oligocene and Miocene reefs and middle Tertiary limestone underlying atolls [1] More recent emergence of the coral reefs is characterised in several cases consistent with sealevel fall at Mangaia, of at least 1.7 m (5 ft 7 in) in the last 3400 years. [2] The northern Suwarrow Atoll rim has portions of reef dated to between 4680 and 4310 years B.P. and at the northeast of the atoll the three ridges are dated from the land out at 4220 years B.P., 3420 years B.P. and from 1250 years B.P. [2] On Mitiaro the centre of the reef flat has regions dated 5140–3620 years B.P. [2]

Contents

Map of the Cook Islands Cook-Islands-map.gif
Map of the Cook Islands

Rarotonga

While not all the islands have firm dates for technical reasons after modern composition and redating studies more is understood. Rarotonga erupted between 1·697 to 1·157 million years ago and so can not be assigned to say the Macdonald hotspot which went through this area 20 million years ago and explains Mangaia nearby. [3] If its formation started with that hotspot it would be an example of rejuvenated volcanism rather than its conventional attribution to the Rarotonga hotspot which is not definite. [3] The main above sea rock type are basalts, mostly olivine basalt but phonolite and trachyte eruptives are found to the south-east of the island and on the lagoon islet of Taa Koka. [1] Phonolite eruptives are also common around the central caldera. [1] There are coastal sedimentary gravels and sands as well as coral deposits. A raised coral deposit 6 ft (1.8 m) near the airfield has been dated at 43,000 years ago. [1]

Mangaia

The 19 million year old [4] basaltic volcanics have been subjected to extensive study as it is the type for a recycled basaltic magma reservoir believed to have elements over 500 million years old that is known as HIMU (high μ = 238U/204Pb) mantle reservoir. [5]

Aitutaki

Aitutaki, which erupted most recently on the carbonate platform of a near-atoll has now been characterised as an example of rejuvenated volcanism with ages from ages from 1.941 to 1·382  million years ago [3] rather than the conventional assignment to the so-called Rarotonga hotspot. However its base volcano was a hot spot volcano that erupted 9·39 million years ago in expected time sequence in the Arago hotspot series of volcanoes. [3] Aitutaki, a high island, has been described as a near-atoll, with 85% of the area within the reef as a lagoon, with in its centre island composed primarily of volcanic rocks, as well as the two smaller volcanic islands of Moturakau and Rapota, and some smaller carol sand islands. [3]

Arago hotspot islands

The Arago hotspot which has a northern track through the Cook Islands area is the younger, in this area of the Pacific, of the two definite volcanic hot spots that contributed to the formation of most of the southern Cook Islands. [3] The Arago hotspot Cook Islands are:

  1. Palmerston
  2. Aitutaki (9·39 Ma) [3]
  3. Atiu (7.44 to 7·20 Ma) [3]
  4. Manaue
  5. Takutea
  6. Atiu
  7. Mitiaro
  8. Mauke

Northern Island Group

These are the islands of Manihiki, Nassau, Penrhyn atoll,Pukapuka, Rakahanga and Suwarrow and likely have limestone caps to their large, old volcanoes erupting from the early Tertiary that are now coral atolls. The largest volcano is Penrhyn rising 16,000 ft (4,900 m) from the sea floor. [1]

See also

  1. Cook Islands
  2. Geography of the Cook Islands
  3. Geology of the Pacific Ocean

Related Research Articles

<span class="mw-page-title-main">Geography of the Cook Islands</span>

The Cook Islands can be divided into two groups: the Southern Cook Islands and the Northern Cook Islands. The country is located in Oceania, in the South Pacific Ocean, about halfway between Hawaii and New Zealand.

<span class="mw-page-title-main">Geography of Samoa</span>

The Samoan archipelago is a chain of 16 islands and numerous seamounts covering 3,123 km2 (1,206 sq mi) in the central South Pacific, south of the equator, about halfway between Hawaii and New Zealand, forming part of Polynesia and of the wider region of Oceania. The islands are Savaiʻi, Upolu, Tutuila, ’Uvea, Taʻū, Ofu, Olosega, Apolima, Manono, Nuʻutele, Niulakita, Nuʻulua, Namua, Fanuatapu, Rose Atoll, Nu'ulopa, as well as the submerged Vailuluʻu, Pasco banks, and Alexa Bank.

<span class="mw-page-title-main">Rarotonga</span> Island of the Cook Islands

Rarotonga is the largest and most populous of the Cook Islands. The island is volcanic, with an area of 67.39 km2 (26.02 sq mi), and is home to almost 75% of the country's population, with 10,898 of a total population of 15,040. The Cook Islands' Parliament buildings and international airport are on Rarotonga. Rarotonga is a very popular tourist destination with many resorts, hotels and motels. The chief town, Avarua, on the north coast, is the capital of the Cook Islands.

<span class="mw-page-title-main">Evolution of Hawaiian volcanoes</span> Processes of growth and erosion of the volcanoes of the Hawaiian islands

The fifteen volcanoes that make up the eight principal islands of Hawaii are the youngest in a chain of more than 129 volcanoes that stretch 5,800 kilometers (3,600 mi) across the North Pacific Ocean, called the Hawaiian–Emperor seamount chain. Hawaiʻi's volcanoes rise an average of 4,600 meters (15,000 ft) to reach sea level from their base. The largest, Mauna Loa, is 4,169 meters (13,678 ft) high. As shield volcanoes, they are built by accumulated lava flows, growing a few meters or feet at a time to form a broad and gently sloping shape.

<span class="mw-page-title-main">Galápagos hotspot</span> Pacific volcanic hotspot

The Galápagos hotspot is a volcanic hotspot in the East Pacific Ocean responsible for the creation of the Galápagos Islands as well as three major aseismic ridge systems, Carnegie, Cocos and Malpelo which are on two tectonic plates. The hotspot is located near the Equator on the Nazca Plate not far from the divergent plate boundary with the Cocos Plate. The tectonic setting of the hotspot is complicated by the Galapagos Triple Junction of the Nazca and Cocos plates with the Pacific Plate. The movement of the plates over the hotspot is determined not solely by the spreading along the ridge but also by the relative motion between the Pacific Plate and the Cocos and Nazca Plates.

<span class="mw-page-title-main">Pitcairn hotspot</span>

The Pitcairn hotspot is a volcanic hotspot located in the south-central Pacific Ocean. Over the past 11 million years, it has formed the Pitcairn-Gambier hotspot chain. It is responsible for creating the Pitcairn Islands and two large seamounts named Adams and Bounty, as well as atolls at Moruroa, Fangataufa and the Gambier Islands. The hotspot is currently located at Adams and Bounty, which are ~60 kilometers East-Southeast of Pitcairn Island.

<span class="mw-page-title-main">Louisville hotspot</span> Volcanic hotspot that formed the Louisville Ridge in the southern Pacific Ocean

The Louisville hotspot is a volcanic hotspot responsible for the volcanic activity that has formed the Louisville Ridge in the southern Pacific Ocean.

<span class="mw-page-title-main">Samoa hotspot</span> Volcanic hotspot located in the south Pacific Ocean

The Samoa hotspot is a volcanic hotspot located in the south Pacific Ocean. The hotspot model describes a hot upwelling plume of magma through the Earth's crust as an explanation of how volcanic islands are formed. The hotspot idea came from J. Tuzo Wilson in 1963 based on the Hawaiian Islands volcanic chain.

<span class="mw-page-title-main">Macdonald hotspot</span> Volcanic hotspot in the southern Pacific Ocean

The Macdonald hotspot is a volcanic hotspot in the southern Pacific Ocean. The hotspot was responsible for the formation of the Macdonald Seamount, and possibly the Austral-Cook Islands chain. It probably did not generate all of the volcanism in the Austral and Cook Islands as age data imply that several additional hotspots were needed to generate some volcanoes.

<span class="mw-page-title-main">Ocean island basalt</span> Volcanic rock

Ocean island basalt (OIB) is a volcanic rock, usually basaltic in composition, erupted in oceans away from tectonic plate boundaries. Although ocean island basaltic magma is mainly erupted as basalt lava, the basaltic magma is sometimes modified by igneous differentiation to produce a range of other volcanic rock types, for example, rhyolite in Iceland, and phonolite and trachyte at the intraplate volcano Fernando de Noronha. Unlike mid-ocean ridge basalts (MORBs), which erupt at spreading centers (divergent plate boundaries), and volcanic arc lavas, which erupt at subduction zones (convergent plate boundaries), ocean island basalts are the result of intraplate volcanism. However, some ocean island basalt locations coincide with plate boundaries like Iceland, which sits on top of a mid-ocean ridge, and Samoa, which is located near a subduction zone.

The sport of football in the country of Cook Islands is run by the Cook Islands Football Association, a full member of the OFC and FIFA. The association administers the national football team. CIFA registered 13 full members as in football clubs, 6 Rarotonga Football Clubs ; 7 Island associations Aitutaki Football Association, Atiu Football Association, Mangaia Football Association, Mauke Football Association, Mitiaro Football Association, Pukapuka Football Association and Rakahanga Football Association; and 3 associate members, Manihiki, Nassau and Penrhyn.

<span class="mw-page-title-main">Mauke</span>

Mauke is an island of the Cook Islands archipelago, lying in the central-southern Pacific Ocean. Part of the Nga-pu-Toru, it is 277 km (172 mi) northeast of Rarotonga.

<span class="mw-page-title-main">Arago hotspot</span> Hotspot in the Pacific Ocean

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

<span class="mw-page-title-main">Wōdejebato</span> Guyot in the Marshall Islands northwest of the smaller Pikinni Atoll

Wōdejebato is a Cretaceous guyot or tablemount in the northern Marshall Islands, Pacific Ocean. Wōdejebato is probably a shield volcano and is connected through a submarine ridge to the smaller Pikinni Atoll 74 kilometres (46 mi) southeast of the guyot; unlike Wōdejebato, Pikinni rises above sea level. The seamount rises for 4,420 metres (14,500 ft) to 1,335 metres (4,380 ft) depth and is formed by basaltic rocks. The name Wōdejebato refers to a sea god of Pikinni.

<span class="mw-page-title-main">Limalok</span> Cretaceous-Paleocene guyot in the Marshall Islands

Limalok is a Cretaceous-Paleocene guyot/tablemount in the southeastern Marshall Islands, one of a number of seamounts in the Pacific Ocean. It was probably formed by a volcanic hotspot in present-day French Polynesia. Limalok lies southeast of Mili Atoll and Knox Atoll, which rise above sea level, and is joined to each of them through a volcanic ridge. It is located at a depth of 1,255 metres (4,117 ft) and has a summit platform with an area of 636 square kilometres (246 sq mi).

<span class="mw-page-title-main">Lo-En</span> Albian–Campanian guyot in the Marshall Islands in the Pacific Ocean

Lo-En or Hess is an Albian–Campanian guyot in the Marshall Islands. One among a number of seamounts in the Pacific Ocean, it was probably formed by a hotspot in what is present-day French Polynesia. Lo-En lies southeast of Eniwetok which rises above sea level, and Lo-En is almost connected to it through a ridge.

<span class="mw-page-title-main">Rarotonga hotspot</span> Volcanic hotspot in the southern Pacific Ocean

The Rarotonga hotspot is a volcanic hotspot in the southern Pacific Ocean. The hotspot is claimed to be responsible for the formation of Rarotonga and some volcanics of Aitutaki but an alternative explanation for these islands most recent volcanics has not been ruled out. Recently alternatives to hotspot activity have been offered for several other intra-plate volcanoes that may have been associated with the Rarotonga hotspot hypothesis.

<span class="mw-page-title-main">Cook Islands tropical moist forests</span>

The Cook Islands tropical moist forests is a tropical and subtropical moist broadleaf forests ecoregion that covers the Southern Cook Islands in the Cook Islands.

<span class="mw-page-title-main">Hotspot highway</span>

The hotspot highway is a term coined in 2010 by Boston University professor Matthew G. Jackson to describe the area of the South Pacific where the postulated tracks of the Samoa, Macdonald, Rurutu, and Rarotonga hotspots all cross paths with one another. While the concept has stood the test of time the key overlapping hot spot tracks appear to be what are now termed the Macdonald hotspot and Arago hotspot which have 10 million years separation but crossed each others paths just south of Samoa. The volcanics of the highway concept are related to the tectonic implications of the breakup of the Ontong Java-Hikurangi-Manihiki large igneous province and of the Pacific large low-shear-velocity province. The tracks are still being redefined by further research and show for example gaps in the Arago hotspot chain with wrong assignment to it rather than the Samoan chain which means we have now little evidence for a cross over between the two.

The Magellan Seamounts stretch from the Mariana Trench to Ita Mai Tai Guyot. Geological studies have demonstrated unique features with implications on understanding of ocean island basalt volcanism. Contracts exist with the International Seabed Authority to exploit the areas potential mineral wealth.

References

  1. 1 2 3 4 5 Wood, B. L. (1967). "Geology of the Cook Islands". New Zealand Journal of Geology and Geophysics. 10 (6): 1429–1445. doi: 10.1080/00288306.1967.10423227 .
  2. 1 2 3 Woodroffe, C.D.; Stoddart, D.R.; Spencer, T.; Scoffin, T. P.; Tudhope, A. W. (1990). "Holocene emergence in the Cook Islands, South Pacific". Coral Reefs. 9 (1): 31–39. Bibcode:1990CorRe...9...31W. doi:10.1007/BF00686719. S2CID   11637511.
  3. 1 2 3 4 5 6 7 8 Jackson, M. G.; Halldórsson, S. A.; Price, A.; Kurz, M. D.; Konter, J. G.; Koppers, A. A. P.; Day, J. M. D. (2020). "Contrasting Old and Young Volcanism from Aitutaki, Cook Islands: Implications for the Origins of the Cook–Austral Volcanic Chain". Journal of Petrology. 61 (3). doi:10.1093/petrology/egaa037.
  4. Hanyu, T; Tatsumi, Y; Senda, R; Miyazaki, T; Chang, Q; Hirahara, Y; Takahashi, T; Kawabata, H; Suzuki, K; Kimura, JI; Nakai, SI (2011). "Geochemical characteristics and origin of the HIMU reservoir: A possible mantle plume source in the lower mantle". Geochemistry, Geophysics, Geosystems. 12 (2). Bibcode:2011GGG....12.AC09H. doi:10.1029/2010GC003252. S2CID   134160019.
  5. Dottin III, JW; Labidi, J; Jackson, MG; Woodhead, J; Farquhar, J (2020). "Isotopic evidence for multiple recycled sulfur reservoirs in the Mangaia mantle plume". Geochemistry, Geophysics, Geosystems. 21 (10). Bibcode:2020GGG....2109081D. doi: 10.1029/2020GC009081 . hdl: 1903/27138 . S2CID   224839231.