The tectonic setting of the Molucca Sea region is unique. It is the only global example of an active arc-arc collision consuming an oceanic basin via subduction in two directions. The Molucca Sea Plate has been subsumed by tectonic microplates, the Halmahera Plate and the Sangihe Plate. The whole complexity is now known as the Molucca Sea Collision Zone.
The existence of Sangihe as a tectonic plate separate from the Molucca Sea Plate is not yet entirely agreed upon by geologists. Some see Sangihe as a western slab of the Molucca Sea Plate, just as they regard Halmahera as an eastern slab of the Molucca Sea Plate. What is apparent to date is that Sangihe was part of the Molucca Sea slab subducted during the Neogene between 45 Ma and 25 Ma.
Seismicity shows the west-dipping Sangihe reaches a depth of about 650 kilometres (400 mi). Both Sangihe and Halmahera are exposed to the surface while the Molucca Sea plate is completely subsumed below these two microplates. The southern boundary of the Molucca Sea Plate is also the boundary of the Philippine Sea Plate and the Australian Plate, and is moving northwards. Since the Sangihe Plate and the Halmahera Plate are in continuity with the Molucca Sea Plate, this implies all three slabs are moving northward in mantle with the Australian Plate.
The Cotabato Trench is an oceanic trench in the Pacific Ocean, off the southwestern coast of Mindanao in the Philippines. Along this trench the oceanic crust of the Sunda Plate beneath the Celebes Sea is being subducted beneath the Philippines Mobile Belt. It forms part of a linked
set of trenches along the western side of the Philippines formed over east-dipping subduction zones, including the Manila Trench and the Negros Trench. At its northern end the rate of convergence across this boundary is about 100 mm per year. It is a relatively young structure, forming during the late Miocene to Pliocene. This age is consistent with the estimated age of the sedimentary rocks in the accretionary wedge associated with the trench and the age of adakitic arc rocks on Mindanao thought to date the onset of subduction.Geology of the Pacific Ocean
The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.The tectonic plates continue to move today. The slowest spreading ridge is the Gakkel Ridge on the Arctic Ocean floor, which spreads at less than 2.5 cm/year (1 in/year), while the fastest, the East Pacific Rise near Easter Island, has a spreading rate of over 15 cm/year (6 in/year).Halmahera Arc
Halmahera Arc is the volcanic arc of the Halmahera region of eastern Indonesia. It is considered to belong to the Halmahera Plate tectonics, within the Molucca Sea Collision Zone.Halmahera Plate
Halmahera Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.List of tectonic plates
This is a list of tectonic plates on the Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks.Manila Trench
The Manila Trench is an oceanic trench in the Pacific Ocean, located west of the islands of Luzon and Mindoro in the Philippines. The trench reaches a depth of about 5,400 metres (17,700 ft), in contrast with the average depth of the South China Sea of about 1,500 metres (4,900 ft). It is created by subduction, in which the Sunda Plate (part of Eurasian Plate) is subducting under the Philippine Mobile Belt, producing this almost N-S trending trench. The convergent boundary is terminated to the north by the Taiwan collision zone, and to the south by the Mindoro terrane (Sulu-Palawan block colliding with SW Luzon). It is an area pervaded by negative gravity anomalies.The Manila Trench is associated with frequent earthquakes, and the subduction zone is responsible for the belt of volcanoes on the west side of the Philippine island of Luzon, which includes Mount Pinatubo.
Convergence between the Philippine Mobile Belt and the Sunda Plate have been estimated using GPS measurements, and this value ranges from ~ 50+ mm/yr in Taiwan, to 100 mm/yr near N. Luzon, and ~ 50 mm/yr near Zambales and ~20+mm/yr near Mindoro island. Plate locking between the Sunda Plate and Luzon is about 1% coupled, almost unlocked as determined by elastic block models, suggesting that the trench absorbs the Philippine Mobile Belt-Eurasian Plate convergence.Marikina Valley Fault System
The Marikina Valley Fault System, also known as the Valley Fault System (VFS), is a dominantly dextral strike-slip fault system in Luzon, Philippines. It extends from Doña Remedios Trinidad, Bulacan in the north and runs through the provinces of Rizal, and the Metro Manila cities of Quezon, Marikina, Pasig, Makati, Taguig and Muntinlupa, and the provinces of Cavite and Laguna that ends in Canlubang.Molucca Sea Collision Zone
The Molucca Sea Collision Zone is postulated by paleogeologists to explain the tectonics of the area based on the Molucca Sea in Indonesia, and adjacent involved areas.Molucca Sea Plate
Located in the western Pacific Ocean near Indonesia, the Molucca Sea Plate has been classified by scientists as a fully subducted microplate that is part of the Molucca Sea Collision Complex. The Molucca Sea Plate represents the only known example of divergent double subduction (DDS), which describes the subduction on both sides of a single oceanic plate.