New Britain subduction zone

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New Britain subduction zone
New Britain subduction zone
Approximate surface projection on Pacific Ocean of subduction features and high earthquake activity near the New Britain subduction zone. The earthquake activity can be due to other tectonic processes than subduction, but does hint at where subducted slabs may be. Key:'"`UNIQ--templatestyles-00000000-QINU`"'
  Up to 70 km (43 mi) deep shallow-focus earthquakes
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  70–300 km (43–186 mi) deep shallow-focus earthquakes
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  More than 300 km (190 mi) deep shallow-focus earthquakes
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  (blue) Active subduction trenches
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  (light blue) Inactive trenches
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  (brown) Selected oceanic floor ridges
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  (yellow) Spreading centers or rifts
Postulated active tectonic transform boundaries are not shown to reduce map complexity as direction of movement can not be shown. Click, then mouse-over shows feature names.'"`UNIQ--ref-00000007-QINU`"'
Etymology New Britain
Tectonics
Plate Australian, New Hebrides
Status Active
Earthquakes Up to Mw 8.1 [1]
Age Miocene-current

The New Britain subduction zone is one of the most recently formed and most active subduction zones on earth, producing great earthquakes (magnitude 8.1 or greater), with potential for tsunami hazard, and being associated with active volcanism, [2] as part of the Pacific Ring of Fire. [3] It has a close relationship to an area of subduction tectonic activity that extends south eastward from New Britain to the Vanuatu subduction zone, involving the north eastern portion of the Australian Plate and its complicated collision dynamics with the south-western portion of the Pacific Plate. [2]

Contents

Geography

The subduction zone is under the eastern part of New Guinea and the islands of New Britain and New Ireland, with associated volcanoes and volcanic seamounts being in the zone, and with the New Britain Trench marking the current subduction boundary. [4] [5] The trench is up to 9,046 m (29,678 ft) deep. [6] To the zone's south east are the San Cristobal Trench (South Solomon Trench) and New Hebrides trenches with beyond them to the east the Solomon Islands and Vanuatu. Further away from the area of current subduction is most of New Guinea itself to the west and to the north and east, the now inactive ocean floor structures of the West Melanesian Trench (Melanesian Trench, Manus Trench), the North Solomon Trench and the Vityaz Trench .

Geology

The active Quaternary New Britain volcanic arc, [7] [4] has volcanic rock composition consistent with a highly depleted source magma from dehydrated oceanic crust with little sediment. [8] The islands have Upper Eocene basement rocks of coralline limestone and volcanics overlain by Upper Oligocene volcaniclastic formations with plutonic intrusions. [4] Carbonates overlay these and were deposited in the Lower to Middle Miocene. [4] Pleistocene to Holocene coral reefs fringe many of the islands. [4] The Solomon Sea bottom is predominantly E-type MORB between 28 and 34 million years old and mudrocks. [7]

Tectonics

The New Britain subduction zone is an example of polarity-reversal subduction initiation, [9] where a new subduction zone is created in a back-arc region with the opposite direction of subduction to that previously operating between two major plates. The major plates in this case are the Australian and Pacific Plates. However a number of minor plates, both active and now inactive (relic) have formed during the change in polarity. These presently active minor plates include the South Bismarck Plate to the north of the New Britain subduction zone and the main subducting Solomon Sea Plate and its adjacent to the east Trobriand Plate. The rates of subduction and roll back are high and are currently for the New Britain Trench, a subduction velocity of 65–120 cm/year (26–47 in/year), a convergence velocity of 2–48 cm/year (0.79–18.90 in/year), and spreading deformation rate in its arc-back- arc area of 10–74 cm/year (3.9–29.1 in/year). [10] In various parts of the trench there is up to 18 cm/year (7.1 in/year) of trench roll back and 20 cm/year (7.9 in/year) of trench advance. [10]

The New Britain subduction zone is a continuum with the south Solomon's and Vanuatu subduction, which are also polarity-reversal. [9] It is possible that the collision to the west of the 30–35 km (19–22 mi) thick Ontong Java Plateau with the Vitiaz Trench from about 25 million years ago initiated this polarity reversal. [9]

However while current tectonics may be well understood, historic tectonics beyond a few million years ago, if that, are poorly understood. The models as developed have been pointed out to be quite inconsistent with the older geology, land fault structures or even the alkaline volcanism of the Tabar, Lihir, Tanga and Feni Islands. [11]

Seismicity

The region is seismically active with twenty two earthquakes with magnitudes equal to or more than 7.5 in 115 years including two Mw 8.1 earthquakes. [1] There is tsunami risk, particularly with great earthquakes. [1] In the area under New Britain and in the area between New Ireland and Bougainville Island the majority of the earthquakes are associated with subduction and in the later portion a subducted slab can be mapped by seismicity to reach a maximum depth close to 660 km (410 mi). [12] There are however many known faults and fault zones, for example the Weitin Fault in Southern New Ireland. This is a transform fault between the South Bismarck Plate and the Pacific Plate, [13] associated with the 16th of November events of the 2000 New Ireland earthquakes. [14] The Bismarck Sea Seismic Delineation is an active transform fault zone that separates the suspected relic North Bismarck Plate (ie Pacific Plate) from the South Bismark Plate to the north of the subduction zone. [14]

Volcanism

Spreading ridges volcanoes map-en.svg
Spreading ridges volcanoes map-en.svg
Approximate map of current volcanic activity near the New Britain subduction zone. Back arc spreading centers are shown as red lines.

The arc volcanoes are grouped into western, Willaumez Peninsula-Mount Ulawun and Rabaul areas. [4] The Gazelle Volcanic Zone extends for 65 km (40 mi) across the central to northern part of the Gazelle Peninsula and the active Rabaul Caldera area to its north had eruptions that destroyed the port in 1994. [15] The Solomon Islands are an active arc volcano chain. The spreading centers in the center of the Woodlark Basin are active volcanically but not manifest as activity on the surface of the ocean. There is probably no seafloor current volcanic activity associated with the Bismarck Sea Seismic Lineation but the Melanesian arc to its north is active. Active volcanism continues into both north-eastern and south-eastern New Guinea.

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<span class="mw-page-title-main">Convergent boundary</span> Region of active deformation between colliding tectonic plates

A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.

<span class="mw-page-title-main">Australian Plate</span> Major tectonic plate separated from Indo-Australian Plate about 3 million years ago

The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately 100 million years ago when India broke away and began moving north. Australia and Antarctica had begun rifting by 96 million years ago and completely separated a while after this, some believing as recently as 45 million years ago, but most accepting presently that this had occurred by 60 million years ago.

<span class="mw-page-title-main">Izu–Bonin–Mariana Arc</span> Convergent boundary in Micronesia

The Izu–Bonin–Mariana (IBM) arc system is a tectonic plate convergent boundary in Micronesia. The IBM arc system extends over 2800 km south from Tokyo, Japan, to beyond Guam, and includes the Izu Islands, the Bonin Islands, and the Mariana Islands; much more of the IBM arc system is submerged below sealevel. The IBM arc system lies along the eastern margin of the Philippine Sea Plate in the Western Pacific Ocean. It is the site of the deepest gash in Earth's solid surface, the Challenger Deep in the Mariana Trench.

The Solomon Sea Plate is a minor tectonic plate to the northwest of the Solomon Islands archipelago in the south Pacific Ocean. It roughly corresponds with the Solomon Sea east of Papua New Guinea. The plate boundaries are associated with high earthquake activity as part of the New Britain subduction zone.

<span class="mw-page-title-main">Caroline Plate</span> Minor oceanic tectonic plate north of New Guinea

The Caroline Plate is a minor tectonic plate that straddles the Equator in the eastern hemisphere located north of New Guinea. It forms a subduction zone along the border with the Bird's Head Plate and other minor plates of the New Guinea region to the south. A transform boundary forms the northern border with the Pacific Plate. Along the border with the Philippine Sea Plate is a convergent boundary that transitions into a rift.

<span class="mw-page-title-main">North Bismarck Plate</span> Small tectonic plate in the Bismarck Sea north of New Guinea

The North Bismarck Plate is a small tectonic plate located in the Bismarck Sea off the northeast coast of New Guinea. It is currently regarded as a relic or inactive plate by most. At one time it was called the Manus Plate, but this term was later used for a modelled microplate at the south east boundary of the North Bismarck Plate.

The South Bismarck Plate is a small tectonic plate located mainly in the southern Bismarck Sea. The eastern part of New Guinea and the island of New Britain are on this plate. It is associated with high earthquake and volcanic activity as part of the New Britain subduction zone within the Pacific Ring of Fire.

<span class="mw-page-title-main">Solomon Islands (archipelago)</span> Archipelago in the South Pacific spreading over two countries

The Solomon Islands (archipelago) is an island group in the western South Pacific Ocean, north-east of Australia. The archipelago is in the Melanesian subregion and bioregion of Oceania and forms the eastern boundary of the Solomon Sea. The many islands of the archipelago are distributed across Papua New Guinea and Solomon Islands (country). The largest island in the archipelago is Bougainville Island, which is a part of the Autonomous Region of Bougainville along with Buka Island, the Nukumanu Islands, and a number of smaller nearby islands. Much of the remainder falls within the territory of Solomon Islands and include the atolls of Ontong Java, Sikaiana, the raised coral atolls of Bellona and Rennell, and the volcanic islands of Choiseul, Guadalcanal, Makira, Malaita, New Georgia, the Nggelas, Santa Isabel, and the Shortlands. The Santa Cruz Islands are not a part of the archipelago.

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Shortly after midnight local time on January 20, 1981, eastern Indonesia was struck by an earthquake known as the 1981 Irian Jaya earthquake. Registering a moment magnitude of 6.7, it killed more than 300 people, damaging structures and buildings across the Irian Jaya province. Indonesia is highly active in terms of seismicity and volcanic eruptions, with a subduction zone and many faults. It is neighbored by several tectonic plates. Such earthquakes pose a significant threat to life in the area through earthquakes and also tsunamis.

<span class="mw-page-title-main">West Melanesian Trench</span> Oceanic trench in the Bismarck Sea north of Papua New Guinea

The West Melanesian Trench is an oceanic trench in the Bismarck Sea north of Papua New Guinea delineating the plate tectonic boundary between the Caroline and North Bismarck plates.

<span class="mw-page-title-main">Kilinailau Trench</span> Ocean trench in south western Pacific Ocean

The Kilinailau Trench is an oceanic trench delineating the former oceanic crust boundary between the Pacific Plate and the now inactive North Bismarck Plate, in the area to the west of Papua New Guinea. To its south west is the inactive North Solomon Trench. The collision of the Ontong Java Plateau in the then subducting oceanic crust of the Pacific Plate, initially to the trench's south-east, changed the plate collision dynamics relative to the then Indo-Australian Plate to the west. Now the Ontong Java Plateau is just to the east of the trench and its great depth of crust appears to explain why subduction stalled here, and moved to the opposite direction along the far side of New Britain and the Solomons. The Melanesian ocean arc ridge structures formed when the trench was active are to its west and would include the north eastern part of New Ireland.

<span class="mw-page-title-main">New Britain Trench</span> Oceanic trench in the southern Pacific Ocean

The New Britain Trench has formed due to subduction of the floor of the Solomon Sea and has some of the highest current seismic activity in the world.

<span class="mw-page-title-main">Geology of the Pacific Ocean</span> Overview about the geology of the Pacific Ocean

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<span class="mw-page-title-main">Woodlark Basin</span> Oceanic basin located to the east of the island of New Guinea

The Woodlark Basin is a young geologic structural basin located in the southwestern Pacific Ocean, found to the southeast of the island country of Papua New Guinea. The basin is an extensional basin that is actively spreading and has a seafloor spreading center. The basin formed between the then Indo-Australian Plate and the Solomon microplate creating the presently independent Woodlark Plate. The Woodlark Basin has a complex geologic history dating back twenty million years to the initial opening of the basin but most of the spreading has happened in the last 3.6 million years.

<span class="mw-page-title-main">Subduction tectonics of the Philippines</span>

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<span class="mw-page-title-main">New Hebrides Trench</span> Oceanic trench in the southern Pacific Ocean

The New Hebrides Trench is an oceanic trench which is over 7.1 km (4.4 mi) deep in the Southern Pacific Ocean. It lies to the northeast of New Caledonia and the Loyalty Islands, to the southwest of Vanuatu, east of Australia, and south of Papua New Guinea and the Solomon Islands. The trench was formed as a result of a subduction zone. The Australian Plate is being subducted under the New Hebrides Plate causing volcanism which produced the Vanuatu archipelago.

The Vanuatu subduction zone is currently one of the most active subduction zones on earth, producing great earthquakes, with potential for tsunami hazard to all coastlines of the Pacific ocean. There are active volcanoes associated with arc volcanism.

<span class="mw-page-title-main">Trobriand Plate</span> Small tectonic plate located to the east of the island of New Guinea

The Trobriand Plate was, and likely is, an independent microplate between New Guinea and the Solomon Islands. It has some unique geology, having the presence of the youngest metamorphic core complexes on earth. If there is presently active subduction between it and the Solomon Plate, at the Trobriand Trough, it continues to be an active microplate. Otherwise in the latest tectonic models it has merged with the Solomon Sea Plate, which becomes somewhat larger than predicted by Bird's 2003 model of Tectonic Plates. As a smaller Solomon Sea Plate is totally underwater, global positioning data can not resolve this issue. The area of the plate is associated with earthquake and volcanic activity as part of the Pacific Ring of Fire.

References

  1. 1 2 3 Heidarzadeh et al. 2015 , p. 5958
  2. 1 2 Li et al. 2023 , Figure 1
  3. ↑ Yang et al. 2018 , Section:1. Introduction
  4. 1 2 3 4 5 6 Lindley 2006 , pp. 403–5
  5. ↑ Holm & Richards 2013 , Section:Discussion
  6. ↑ Yang et al. 2018 , 6. Conclusions
  7. 1 2 Woodhead & Brauns 2004 , Section:Geological setting and samples studied
  8. ↑ Woodhead & Brauns 2004 , Introduction
  9. 1 2 3 Li et al. 2023 , Section: 2.1 Polarity-reversal subduction initiation
  10. 1 2 Li et al. 2023 , Table 2, p482
  11. ↑ Lindley 2006 , pp. 421–2
  12. ↑ Li et al. 2023 , p. 484
  13. ↑ Lindley 2006 , pp. 410–11
  14. 1 2 Park & Mori 2007 , Introduction
  15. ↑ McKee & Duncan 2016 , Introduction
Sources
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