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.
The Tonga Trench is an oceanic trench located in the southwestern Pacific Ocean. It is the deepest trench in the Southern hemisphere and the second deepest on Earth after the Mariana Trench. The fastest plate-tectonic velocity on Earth is occurring at this location, as the Pacific Plate is being subducted westward in the trench.
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At 103 million km2 (40 million sq mi), it is the largest tectonic plate.
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.
The Galapagos Microplate (GMP) is a geological feature of the oceanic crust located at 1°50' N, offshore of the west coast of Colombia. The GMP is collocated with the Galapagos Triple Junction, which is an atypical ridge-ridge-ridge triple junction. At the Galapagos Triple Junction, the Pacific Plate, Cocos Plate, and Nazca Plate meet incompletely, forming two counter-rotating microplates at the junction of the Cocos-Nazca, Pacific-Cocos, and Pacific-Nazca spreading ridges.
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.
The New Hebrides Plate, sometimes called the Neo-Hebridean Plate, is a minor tectonic plate located in the Pacific Ocean. While most of it is submerged as the sea bottom of the North Fiji Basin, the island country of Vanuatu, with multiple arc volcanoes, is on the western edge of the plate. It is bounded on the south-west by the Australian Plate, which is subducting below it at the New Hebrides Trench. The Vanuatu subduction zone is seismically active, producing many earthquakes of magnitude 7 or higher. To its north is the Pacific Plate, north-east the Balmoral Reef Plate and to its east the Conway Reef Plate.
The Marquesas hotspot is a volcanic hotspot in the southern Pacific Ocean. It is responsible for the creation of the Marquesas Islands – a group of eight main islands and several smaller ones – and a few seamounts. The islands and seamounts formed between 5.5 and 0.4 million years ago and constitute the northernmost volcanic chain in French Polynesia.
The Manihiki Plateau is an oceanic plateau in the south-west Pacific Ocean. The Manihiki Plateau was formed by volcanic activity 126 to 116 million years ago during the mid-Cretaceous period at a triple junction plate boundary called the Tongareva triple junction. Initially at 125 million years ago the Manihiki Plateau formed part of the giant Ontong Java-Manihiki-Hikurangi plateau.
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.
The Conway Reef Plate is a small tectonic plate (microplate) located in the south Pacific west of Fiji. The western boundary is with the New Hebrides Plate while the eastern is with the Australian Plate. A short transform boundary also exists with the Balmoral Reef Plate. Much of the plate underlies the south central portion of the North Fiji Basin.
The Maoke Plate is a small tectonic plate located in western New Guinea underlying the Sudirman Range from which the highest mountain on the island- Puncak Jaya rises. To its east was proposed a convergent boundary with the Woodlark Plate, although this is now best modelled after further studies as a boundary with an enlarged Solomon Sea Plate or a new microplate called the Trobriand Plate. To the south lies a transform boundary with the Australian Plate and the Bird's Head Plate lies to the west.
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.
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.
The North Fiji Basin (NFB) is an oceanic basin west of Fiji in the south-west Pacific Ocean. It is an actively spreading back-arc basin delimited by the Fiji islands to the east, the inactive Vitiaz Trench to the north, the Vanuatu/New Hebrides island arc to the west, and the Hunter fracture zone to the south. Roughly triangular in shape with its apex located at the northern end of the New Hebrides Arc, the basin is actively spreading southward and is characterised by three spreading centres and an oceanic crust younger than 12 Ma. The opening of the NFB began when a slab roll-back was initiated beneath the New Hebrides and the island arc started its clockwise rotation. The opening of the basin was the result of the collision between the Ontong Java Plateau and the Australian Plate along the now inactive Solomon–Vitiaz subduction system north of the NFB. The NFB is the largest and most developed back-arc basin of the south-west Pacific. It is opening in a complex geological setting between two oppositely verging subduction systems, the New Hebrides/Vanuatu and Tonga trenches and hence its ocean floor has the World's largest amount of spreading centres per area.
Oblique subduction is a form of subduction for which the convergence direction differs from 90° to the plate boundary. Most convergent boundaries involve oblique subduction, particularly in the Ring of Fire including the Ryukyu, Aleutian, Central America and Chile subduction zones. In general, the obliquity angle is between 15° and 30°. Subduction zones with high obliquity angles include Sunda trench and Ryukyu arc.
The Lau-Colville Ridge is an extinct oceanic ridge located on the oceanic Australian Plate in the south-west Pacific Ocean extending about 2,700 km (1,700 mi) from the south east of Fiji to the continental shelf margin of the North Island of New Zealand. It was an historic subduction boundary between the Australian Plate and the Pacific Plate and has important tectonic relationships to its east where very active spreading and subduction processes exist today. It is now the inactive part of an eastward-migrating, 100 million year old Lau-Tonga-Havre-Kermadec arc/back-arc system or complex and is important in understanding submarine arc volcanism because of these relationships. To its west is the South Fiji Basin whose northern bedrock is Oligocene in origin.
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.
