2012 Kermadec Islands eruption

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2012 Kermadec Islands eruption
Havre Seamount Eruption 19 July 2012 with labels.jpg
NASA image of Havre Seamount eruption and initial formation of pumice raft
Volcano Havre Seamount
Start date18 July 2012
Start timeMorning
End date19 July 2012
Type Submarine
Location Kermadec Islands
31°07′13″S179°58′07″W / 31.12028°S 179.96861°W / -31.12028; -179.96861
VEI 1

The 2012 Kermadec Islands eruption was a major undersea volcanic eruption that was produced by the previously little-known Havre Seamount near the L'Esperance and L'Havre Rocks [1] in the Kermadec Islands of New Zealand. [2] [3] The large volume of low density pumice produced by the eruption accumulated as a large area of floating pumice, a pumice raft, that was originally covering a surface of 400 square kilometres (150 square miles), spread to a continuous float of between 19,000 and 26,000 square kilometres (7,500 and 10,000 sq mi) [4] [5] and within three months dispersed to an area of more than twice the size of New Zealand. [6]

Contents

The thickness of the raft may initially have been as high as 3.5 metres (11 feet) and was reduced to around 0.5 metres (1 foot 8 inches) within a month. [7]

Three months after the eruption, the mass had dispersed into very dilute rafts and ribbons of floating pumice clasts. Most pumice clasts became waterlogged and sank to the sea floor, while some flocks have stranded in the Tonga islands, on the northern shores of New Zealand, and eventually on the eastern coast of Australia one year after the eruption. [7]

While the eruption is officially rated as a VEI 1 by the Smithsonian Institution, studies have found that approximately 1.5 cubic kilometres of material erupted, which correlates to a VEI 5 eruption. [8]

Eruption

Bathymetric map of Kermadec islands and seamounts Kermadec Arc.jpg
Bathymetric map of Kermadec islands and seamounts

The eruption of the Havre Seamount was not initially noticed by scientists, and volcanologists were not even aware that the Havre Seamount was an active submarine volcano. [2] After the pumice raft was detected, researchers retrospectively examined satellite imagery and past seismic activity in an attempt to pinpoint the time and location of the eruption that produced the pumice raft. [2] Seismologists discovered a cluster of earthquakes (ranging in magnitude between 3.0 and 4.8) that occurred 18–19 July 2012. [2] [9] These earthquakes were consistent with magma rising into a magma chamber prior to eruption. [2] Analysis of satellite imagery showed an ash plume appear on 18 July 2012 and conclude several days later. [2] [9] Although some volcanologists initially believed that the eruption might have occurred at the Monowai Seamount, this possibility was later ruled out. [9] It is also believed that the eruption was unrelated to the 2012 Te Māri eruption at New Zealand's Mount Tongariro. [10]

In 2015 a scientific expedition set out to study changes of seafloor topography in the area surrounding Havre Seamount. [6] The same group of researchers mapped the distribution of the floating pumice blocks driven by wind, ocean currents and eddies. [7]

Pumice raft

Kermadec Islands pumice raft on 12 August 2012. Raft can be seen as fibrous tendrils primarily in lower right quadrant; Raoul Island can be seen as green dot near upper right. KermadecIsland.A2012225.2140.250m.jpg
Kermadec Islands pumice raft on 12 August 2012. Raft can be seen as fibrous tendrils primarily in lower right quadrant; Raoul Island can be seen as green dot near upper right.

Scientists were not aware that any eruption had occurred until a huge pumice raft was sighted and photographed at 14:40 NZST on 31 July 2012 by Maggie de Grauw while on a commercial flight from Faleolo, Samoa to Auckland, New Zealand. She emailed her pictures to Dr Scott Bryan, senior research fellow at Queensland University of Technology. After discussion, it was ascertained that the raft was around 1,000 kilometres (620 miles) north of Auckland. Bryan then contacted Olivier Hyvernaud from the Laboratoire de Géophysique, Tahiti, who confirmed the location from Terra/MODIS imagery from NASA. The raft was subsequently sighted by members of the New Zealand Defence Force on 9 August 2012 [11] —several weeks after the eruption had occurred. [2] It was spotted by an Orion aircraft and then approached and sampled by the strategic sealift ship HMNZS Canterbury. [9] The pumice raft measured approximately 480 kilometres (300 mi) in length and more than 48 kilometres (30 mi) in width, making the floating island larger in surface area than Israel. [10] [11] An officer in the Royal Australian Navy said that it was "the weirdest thing [he had] seen in 18 years at sea". [10] [11]

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Kermadec Islands Subtropical island arc in the South Pacific Ocean

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L'Esperance Rock, formerly known as French Rock and Brind Rock,(named after William Brind) is the southernmost islet in the Kermadec Islands, to the north of New Zealand. It is 80 km (50 mi) south of Curtis Island and 600 km (370 mi) northeast of East Cape on New Zealand's North Island. The smaller L'Havre Rock lies 8 km (5 mi) to the north-west of L'Esperance; it is a reef that barely reaches the surface. L'Esperance Rock is 250 m (820 ft) in diameter with an area of 4.8 ha. It rises to a height of 70 m (230 ft).

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Monowai (seamount) Volcanic seamount north of New Zealand

Monowai Seamount is a volcanic seamount to the north of New Zealand. It is formed by a large caldera and a volcanic cone just south-southeast from the caldera. The volcanic cone rises to depths of up to 100 metres (330 ft) but its depth varies with ongoing volcanic activity, including sector collapses and the growth of lava domes. The seamount and its volcanism were discovered after 1877, but only in 1980 was it named "Monowai" after a research ship of the same name.

Helen Bostock

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Havre Seamount Volcanic seamount in the Kermadec Islands group

Havre Seamount is an active volcanic seamount lying within the Kermadec Islands group of New Zealand, in the south-west Pacific Ocean, on the Tonga-Kermadec Ridge. Its most recent eruption took place in July 2012.

Volcano F is a submarine volcano in the Tonga Islands of the South Pacific Ocean. It is located 50 km (31 mi) northwest of Vavaʻu, between Late and Fonualei on the Tofua ridge. It is part of the highly active Kermadec-Tonga subduction zone and its associated volcanic arc, which extends from New Zealand north-northeast to Fiji, and is formed by the subduction of the Pacific Plate under the Indo-Australian Plate.

Macauley Island Volcanic island in New Zealands Kermadec Islands

Macauley Island is a volcanic island in New Zealand's Kermadec Islands, approximately halfway between New Zealand's North Island and Tonga in the southwest Pacific Ocean. It is part of a larger submarine volcano that features a 10.5 by 7 kilometres wide underwater caldera northwest of Macauley Island. Two islets, Haszard Island and Newcome Rock, lie east offshore of Macauley Island. The island is mostly surrounded by high cliffs that make accessing it difficult; the inland parts are mostly gently sloping terrain covered with ferns and grasses.

Curtis Island (New Zealand) Island in New Zealand

Curtis Island is an island in the southwest Pacific. It is a volcanic island which, together with neighbouring Cheeseman Island, belongs to the Kermadec Islands, an outlying island group of New Zealand. It is a volcanic island with a fumarolically active crater, while vegetated slopes are nested by seabirds. There are uncertain reports of eruptions and the island has been uplifted by about 18 m (59 ft) during the past 200 years.

South Kermadec Ridge Seamounts Missing volcanic geological feature

The South Kermadec Ridge Seamounts are a continuation of the volcanic island arc, formed at the convergent boundary where the Pacific Plate subducts under the Indo-Australian Plate. The subducting Pacific Plate created the Kermadec Trench, the second deepest submarine trench, to the east of the islands. The seamounts lie along the western aspect of the undersea Kermadec Ridge, which runs southwest from the Kermadec Islands towards the North Island of New Zealand and northeast towards Tonga. This area of the Kermadec Arc - Havre Trough is a relatively young oceanic arc- back-arc system as it became active in the Quaternary. The seamounts include:

References

  1. ↑ Science Direct map of Kermadec Islands and Seamounts Archived 2 February 2013 at archive.today
  2. 1 2 3 4 5 6 7 Klemetti, Erik (13 August 2012). "Havre Seamount: The Source of Kermadec Island Pumice Raft?". Wired. Retrieved 13 August 2012.
  3. ↑ Bryner, Jeanna (14 August 2012). "'Raft' in Pacific Found, NASA Says". Live Science . Retrieved 14 August 2012.
  4. ↑ Memmott, Mark (10 August 2012). "7,500 Square Miles of Pumice Floating in Pacific Is 'Weirdest Thing I've Seen'". NPR . Retrieved 13 August 2012.
  5. ↑ "Massive Rock Raft Found Floating off New Zealand". ABC News . Associated Press. 10 August 2012. Archived from the original on 12 August 2012. Retrieved 13 August 2012.
  6. 1 2 Website of the expedition Mesh
  7. 1 2 3 Jutzeler, Martin; Marsh, Robert; Carey, Rebecca J.; White, James D. L.; Talling, Peter J.; Karlstrom, Leif (22 April 2014). "On the fate of pumice rafts formed during the 2012 Havre submarine eruption". Nature Communications . 5 (3660): 3660. doi:10.1038/ncomms4660. PMC   3997806 . PMID   24755668.
  8. ↑ Carey, Rebecca; Soule, S. Adam; Manga, Michael; White, James D. L.; McPhie, Jocelyn; Wysoczanski, Richard; Jutzeler, Martin; Tani, Kenichiro; Yoerger, Dana; Fornari, Daniel; Caratori-Tontini, Fabio (5 January 2018). "The largest deep-ocean silicic volcanic eruption of the past century". Science Advances . 4 (1): e1701121. doi:10.1126/sciadv.1701121. ISSN   2375-2548. PMC   5762192 . PMID   29326974.
  9. 1 2 3 4 Cooke, Michelle (11 August 2012). "Scientists rock theory on pumice raft". Stuff.co.nz . Retrieved 13 August 2012.
  10. 1 2 3 Gannon, Megan (10 August 2012). "Huge pumice rock 'island' seen floating in South Pacific: New Zealand's Royal Navy spots raft larger than Israel — but no one knows where it's from". NBC News . Retrieved 13 August 2012.
  11. 1 2 3 Gannon, Megan (13 August 2012). "Mystery Rock Shelf Floating in Pacific: Floating pumice rocks are covering an area larger than Israel in the South Pacific". Discovery News . Archived from the original on 15 August 2012. Retrieved 13 August 2012.
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