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. MoluccaSeaCollisionZone

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 province of Indonesia, and Sofifi, the capital of the province, is located on the west coast of the island. Ha ...

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 oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...

, the Molucca Sea 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 world's eleventh-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of Mindanao and the Sulu ...

) to the west,

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

Celebes Sea The Celebes Sea, (; ms, Laut Sulawesi, id, Laut Sulawesi, fil, Dagat Selebes) 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 b ...

to the west. To the north is the

Philippine Sea The Philippine Sea is a marginal sea of the Western Pacific Ocean east of the Philippine archipelago (hence the name), the largest in the world, occupying an estimated surface area of . The Philippine Sea Plate forms the floor of the sea. I ...

and to the east is the Halmahera Sea. Situated south of

Mindanao Mindanao ( ) ( Jawi: مينداناو) is the second-largest island in the Philippines, after Luzon, and seventh-most populous island in the world. Located in the southern region of the archipelago, the island is part of an island group of ...

, 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 above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found i ...

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 arcs. 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 Forearc is a plate tectonic term referring to a region between an oceanic trench, also known as a subduction zone, and the associated volcanic arc. Forearc regions are present along a convergent margins and eponymously form 'in front of' the v ...

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 that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found ...

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