The Banda Arc (main arc, Inner, and Outer) is a set of island arcs in eastern

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

. It is the result of the collision of a

continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions In geography, regions, otherwise referred to as zones, lands or territories, are areas t ...

and an intra-oceanic

island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle alon ...

. The presently active arc is located on what appears to be

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic ...

whereas the associated subduction trench is underlain by

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial'' be ...

. The convergence of the Indo-Australian plates and

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

resulted in the formation of the Sunda and Banda

s. The transitional zone between the arcs is located south of Flores Island and is characterized by the change in the

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

regime along the boundary.

Terminology

Some academic literature refers to the arcs by location – so that main arc can be referred to as the 'southern', the 'western' Situated at the centre of three converging and colliding major

tectonic plates Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...

, Indo-Australia,

Pacific 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 contine ...

, the Banda arc includes young

enclosed by a volcanic inner arc, outer arc islands and a trough parallel to the Australian

continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

. It is a complex subduction setting (where one plate moves under another, sinking into the Earth's mantle), with possibly the largest fold on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, extending to a depth of about , in a subducted plate.

Inner and outer arcs

The Banda Arc is a double

formed by the collision of the

Indo-Australian plate The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...

with the

Eurasian plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

. Principal islands include

Timor Timor is an island at the southern end of Maritime Southeast Asia, in the north of the Timor Sea. The island is divided between the sovereign states of East Timor on the eastern part and Indonesia on the western part. The Indonesian part, also ...

, Flores, and

Seram Seram (formerly spelled Ceram; also Seran or Serang) is the largest and main island of Maluku province of Indonesia, despite Ambon Island's historical importance. It is located just north of the smaller Ambon Island and a few other adjacent is ...

. * The Inner Banda Arc consists of a string of recent and active volcanic islands from Komodo to Kekeh-besar of the

Barat Daya Islands The Barat Daya Islands ( id, Kepulauan Barat Daya) are a group of islands in the Maluku province of Indonesia. The Indonesian phrase ''barat daya'' means 'south-west'. Geography These islands are located off the eastern end of East Timor. Wetar ...

, including Flores, Solor, Alor,

Wetar Wetar is a tropical island which belongs to the Indonesian province of Maluku and is the largest island of the Maluku Barat Daya Islands (literally ''Southwest Islands'') of the Maluku Islands. It lies east of the Lesser Sunda Islands, which i ...

, and Damar. * The Outer Banda Arc is older and non-volcanic. It overlies the margin of the Precambrian

craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging an ...

that makes up much of the continent of Australia. It stretches from

Savu Savu ( id, Sawu, also known as Sabu, Havu, and Hawu) is the largest of a group of three islands, situated midway between Sumba and Rote, west of Timor, in Indonesia's eastern province, East Nusa Tenggara. Ferries connect the islands to Waingapu ...

through Rote,

, Leti, Babar,

Tanimbar The Tanimbar Islands, also called ''Timur Laut'', are a group of about 65 islands in the Maluku province of Indonesia. The largest and most central of the islands is Yamdena; others include Selaru to the southwest of Yamdena, Larat and F ...

, and the

Kai Islands The Kai Islands (also Kei Islands) of Indonesia are a group of islands in the southeastern part of the Maluku Islands, located in the province of Maluku. The Moluccas have been known as the Spice Islands due to regionally specific plants such ...

, before turning west to

Ambon Ambon may refer to: Places * Ambon Island, an island in Indonesia ** Ambon, Maluku, a city on Ambon Island, the capital of Maluku province ** Governorate of Ambon, a colony of the Dutch East India Company from 1605 to 1796 * Ambon, Morbihan, a c ...

, and

Buru Buru (formerly spelled Boeroe, Boro, or Bouru) is the third largest island within the Maluku Islands of Indonesia. It lies between the Banda Sea to the south and Seram Sea to the north, west of Ambon and Seram islands. The island belongs to ...

. The outer arc is geologically associated with the Australian continent, though it is a more recent accretion than the neighbouring

Aru Islands The Aru Islands Regency ( id, Kabupaten Kepulauan Aru) is a group of about 95 low-lying islands in the Maluku Islands of eastern Indonesia. It also forms a regency of Maluku Province, with a land area of . At the 2011 Census the Regency had a ...

. The resulting feature is a 180-degree

, which is more than long. Geographically, it stretches across eastern

, and is delimited by an active inner

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...

arc. The outer arc contains numerous

island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island ...

s, and its internal geologic structure contains young

exclusively.

References

* {{authority control Plate tectonics Island arcs Archipelagoes of Indonesia Arcs of Indonesia

Terminology

Inner and outer arcs

See also

References