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.

Tectonic setting

The Molucca Sea plate is one of many tectonic features that compose the Molucca Sea Collision Complex, which refers to the tectonic relationship of the Sangihe plate, Halmahera plate, and the Molucca Sea plate, in addition to the volcanic

Halmahera Halmahera, formerly known as Jilolo, Gilolo, or Jailolo, is the largest island in the Maluku Islands. It is part of the North Maluku Provinces of Indonesia, province of Indonesia, and Sofifi, the capital of the province, is located on the west coa ...

and Sangihe Arcs. The southeast moving Sangihe plate is situated along the western boundary of the Molucca Sea plate. The northwest moving Halmahera plate is situated along the eastern boundary of the Molucca Sea plate. In the western

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, the

Molucca Sea The Molucca Sea (Indonesian language, Indonesian: ''Laut Maluku'') is located in the western Pacific Ocean, around the vicinity of Indonesia, specifically bordered by the Indonesian Islands of Sulawesi, Celebes (Sulawesi) to the west, Halmahera t ...

is bordered by the Indonesian Islands of Celebes (

Sulawesi Sulawesi ( ), also known as Celebes ( ), is an island in Indonesia. One of the four Greater Sunda Islands, and the List of islands by area, world's 11th-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of Min ...

) to the west,

to the east, and the Sula Islands to the south. The Molucca Sea borders the

Banda Sea The Banda Sea (, , ) is one of four seas that surround the Maluku Islands of Indonesia, connected to the Pacific Ocean, but surrounded by hundreds of islands, including Timor, as well as the Halmahera Sea, Halmahera and Ceram Seas. It is about ...

to the south and the

Celebes Sea The Celebes Sea ( ; ) or Sulawesi Sea (; ) of the western Pacific Ocean is bordered on the north by the Sulu Archipelago and Sulu Sea and Mindanao Island of the Philippines, on the east by the Sangihe Islands chain, on the south by Sulawes ...

to the west. To the north is the

Philippine Sea The Philippine Sea is a List of seas#Marginal seas by ocean, marginal sea of the Pacific Ocean, Western Pacific Ocean east of the list of islands of the Philippines, Philippine Archipelago (hence the name) and the List of seas#Largest seas ...

and to the east is the

Halmahera Sea The Halmahera Sea is a regional sea located in the central eastern part of the Australasian Mediterranean Sea. It is centered at about 1°S and 129°E and is bordered by the Pacific Ocean to the north, Halmahera to the west, Waigeo and West ...

. Situated south of

Mindanao Mindanao ( ) is the List of islands of the Philippines, second-largest island in the Philippines, after Luzon, and List of islands by population, seventh-most populous island in the world. Located in the southern region of the archipelago, the ...

, the Molucca Sea is a narrow basin underlined by a north‐south

ophiolitic An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found in the name of o ...

ridge, which uplifts the central region of the basin.

Plate mechanics

While the scientific community has not come to a consensus as to when the Molucca Sea plate became fully subducted, the dominant theory is that the Molucca Sea plate has been completely subducted beneath the overriding

and Sangihe plates. When actively subducting, the crustal collision of the Molucca Sea plate was formed by surface intersection of "oppositely dipping Benioff zones” (also known as divergent double subduction) which results in the Sangihe and Halmahera

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc ...

s. The force exerted by the thick overlying collision complex of the Halmahera and Sangihe plates effectively depressed the crust of the Molucca Sea plate. The plate itself features an asymmetrical morphology, configured in an inverted U-shape. The arc-arc collision zone of the Molucca Sea plate is characterized as a thick, low velocity layer, which is highly variable in density. The variable in density of the Molucca Sea plate led to different subduction velocities on the two sides. Divergent Double Subduction may facilitate various tectonic processes, including closure of ocean basins,

accretion Accretion may refer to: Science * Accretion (astrophysics), the formation of planets and other bodies by collection of material through gravity * Accretion (meteorology), the process by which water vapor in clouds forms water droplets around nucl ...

and amalgamation of volcanic arcs, and growth of continents.

Earthquakes

Historically, the Molucca Sea plate has experienced hundreds of earthquakes ranging in magnitude. The most recent large earthquake occurred in January 2017 when a 7.3 magnitude earthquake deep beneath the

, which the USGS attributed to the “''deep reverse faulting within the inclined seismic zone defining the deep limit of the Molucca Sea microplate beneath the Celebes Sea Basin.''”

Geology

The geologic characteristics displayed on the surrounding islands provide insight regarding the complex plate movement of the divergent double subducting plate. Detached

series and thick melanges are overlain by

forearc A forearc is a region in a subduction zone between an oceanic trench and the associated volcanic arc. Forearc regions are present along convergent margins and eponymously form 'in front of' the volcanic arcs that are characteristic of convergen ...

deposits; subduction-driven east–west shortening of the Snellius Plateau caused the thrust melanges to reactivate and deform the

series. Exposed

rocks can be found on the islands of the submarine Talaud-Mayu Ridge, which bisects the arc-arc collision zone of the Molucca Sea plate; these

ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle (Earth), upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is ...

s provide insight regarding the relationship between earthquakes and uplift surrounding the plate.

References

{{DEFAULTSORT:Molucca Sea plate Tectonic plates Geology of the Pacific Ocean Geology of Indonesia Molucca Sea

Tectonic setting

Plate mechanics

Earthquakes

Geology

See also

References