Continental crustal fragments, partly synonymous with microcontinents, [1] are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. [2]
Continental fragments and microcontinent crustal compositions are very similar to those of regular continental crust. The rifting process that caused the continental fragments to form most likely impacts their layers and overall thickness along with the addition of mafic intrusions to the crust. Studies have determined that the average crustal thickness of continental fragments is approximately 24.8 ± 5.7 kilometres (15.4 ± 3.5 mi). [3] The sedimentary layer of continental fragments can be up to 5 kilometres (3.1 mi) thick and can overlay two to three crustal layers. Continental fragments have an average crustal density of 2.81 g/cm3 (0.102 lb/cu in) which is very similar to that of typical continental crust.
Strike-slip fault zones cause the fragmentation of microcontinents. The zones link the extensional zones where continental pieces are already isolated through the remaining continental bridges. Additionally, they facilitate quick crustal thinning across narrow zones and near-vertical strike-slip-dominated faults. They develop fault-block patterns that slice the portion of continent into detachable slivers. The continental fragments are located at various angles from their transform faults. [4]
Some microcontinents are fragments of Gondwana or other ancient cratonic continents; examples include Madagascar; the northern Mascarene Plateau, which includes the Seychelles Microcontinent; and the island of Timor. [5] Other islands, such as several in the Caribbean Sea, are composed largely of granitic rock as well, but all continents contain both granitic and basaltic crust, and there is no clear dividing line between islands and microcontinents under such a definition. The Kerguelen Plateau is a large igneous province formed by a volcanic hotspot; however, it was associated with the breakup of Gondwana and was for a time above water, so it is considered a microcontinent, though not a continental fragment. [6] [7] Other hotspot islands such as the Hawaiian Islands and Iceland are considered neither microcontinents nor continental fragments. Not all islands can be considered microcontinents: Borneo, the British Isles, Newfoundland, and Sri Lanka, for example, are each within the continental shelf of an adjacent continent, separated from the mainland by inland seas flooding its margins. [8]
Several islands in the eastern Indonesian Archipelago are considered continental fragments, although this designation is controversial. The archipelago is home to numerous microcontinents with complex geology and tectonics. This makes it complicated to classify landmasses and determine causation for the formation of the landmass. [9] These include southern Bacan, Banggai-Sulu Islands (Sulawesi), the Buru-Seram-Ambon complex (Maluku), Obi, Sumba, and Timor (Nusa Tenggara) [10]
An island or isle is a piece of subcontinental land completely surrounded by water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island in a river or a lake island may be called an eyot or ait, and a small island off the coast may be called a holm. Sedimentary islands in the Ganges Delta are called chars. A grouping of geographically or geologically related islands, such as the Philippines, is referred to as an archipelago.
The Maluku Islands or the Moluccas are an archipelago in the eastern part of Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located east of Sulawesi, west of New Guinea, and north and east of Timor. Lying within Wallacea, the Moluccas have been considered as a geographical and cultural intersection of Asia and Oceania.
The Barat Daya Islands are a group of islands in the Maluku province of Indonesia. The Indonesian phrase barat daya means 'south-west'.
This is a list of the extreme points of Eurasia, the points that are farther north, south, east or west than any other location on the continent. Some of these locations are open to debate, owing to the diverse definitions of Europe and Asia.
Adonara is an island in the Lesser Sunda Islands of Indonesia, located east of the larger island of Flores in the Solor Archipelago. To the east lies Lembata, formerly known as Lomblen. Adonara is the highest of the islands of the archipelago, reaching an altitude of 1,659 metres, and it has an area of 529.75 km2. It is situated administratively in the East Flores Regency of East Nusa Tenggara province.
Rinca, also known as Rincah, Rindja, Rintja and Pintja, is a small island near Komodo and Flores island, East Nusa Tenggara, Indonesia, within the West Manggarai Regency. It is one of the three largest islands included in Komodo National Park. The island is famous for Komodo dragons, giant lizards that can measure up to 3 metres (9.8 ft) long. Rinca is also populated with many other species such as wild pigs, buffalos and many birds.
Sangeang Api is an active complex volcano on the island of Sangeang in Indonesia. It consists of two volcanic cones, 1,949 metres (6,394 ft) Doro Api and 1,795 m (5,889 ft) Doro Mantoi. Sangeang Api is one of the most active volcanoes in the Lesser Sunda Islands. It erupted in 1988 and the island's inhabitants were evacuated. Between its first recorded eruption in 1512 and 1989 it erupted 17 times. It erupted again during December 2012 and May 2014.
Geologically, the Sunda Shelf is a south-eastern extension of the continental shelf of Mainland Southeast Asia. Major landmasses on the shelf include Bali, Borneo, Java, Madura, and Sumatra, as well as their surrounding smaller islands. It covers an area of approximately 1.85 million km2. Sea depths over the shelf rarely exceed 50 metres and extensive areas are less than 20 metres resulting in strong bottom friction and strong tidal friction. Steep undersea gradients separate the Sunda Shelf from the Philippines, Sulawesi, and the Lesser Sunda Islands.
The Kerguelen Plateau, also known as the Kerguelen–Heard Plateau, is an oceanic plateau and large igneous province (LIP) located on the Antarctic Plate, in the southern Indian Ocean. It is about 3,000 km (1,900 mi) to the southwest of Australia and is nearly three times the size of California. The plateau extends for more than 2,200 km (1,400 mi) in a northwest–southeast direction and lies in deep water.
Solor is a volcanic island located off the eastern tip of Flores island in the Lesser Sunda Islands of Indonesia, in the Solor Archipelago. The island supports a small population that has been whaling for hundreds of years. They speak the languages of Adonara and Lamaholot. There are at least five volcanoes on this island which measures only 40 kilometres by 6 kilometres. The island's area is 226.34 square kilometres, and it had a population of 34,029 at the 2020 Census. The official estimate as at mid 2022 was 35,891.
Pamana Island is a small island off Rote Island in Indonesia's East Nusa Tenggara province of Lesser Sunda Islands, and the southernmost point of Asia. It lies exactly on latitude 11°S. Administratively this island is part of Rote Ndao Regency. It borders the Ashmore and Cartier Islands to the south.
Moyo is an island in Indonesia's West Nusa Tenggara province. It is off the north coast of Sumbawa Island, and has an area of 349 km2. Moyo Island is located in Sumbawa Regency within the Nusa Tenggara province, just north of Sumbawa. The island has an area of 32,044 hectares, about 8° south of the equator. The island is proposed as part of Moyo Satonda National Park along with Satonda Island.
Timor is an island in South East Asia. Geologically considered a continental crustal fragment, it lies alongside the Sunda shelf, and is the largest in a cluster of islands between Java and New Guinea. European colonialism has shaped Timorese history since 1515, a period when it was divided between the Dutch in the west of the island and the Portuguese in the east.
Zealandia, also known as Te Riu-a-Māui (Māori) or Tasmantis, is an almost entirely submerged mass of continental crust in Oceania that subsided after breaking away from Gondwana 83–79 million years ago. It has been described variously as a submerged continent, continental fragment, and microcontinent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. A 2021 study suggests Zealandia is 1 billion years old, about twice as old as geologists previously thought.
This is a list of articles related to plate tectonics and tectonic plates.
The Seychelles Microcontinent is a microcontinent underlying Seychelles in the western Indian Ocean made of Late Precambrian rock.
Avicennia rumphiana is a species of tropical mangrove in the family Acanthaceae. It is considered vulnerable by the IUCN Red List of Threatened Species in the 2008 assessment. As of March 2022, Plants of the World Online considered it to be only a variety of Avicennia marina, Avicennia marina var. rumphiana. In the Malay language it is known as api api bulu.
The Lesser Sunda Islands, also known as Nusa Tenggara Islands, are an archipelago in Maritime Southeast Asia, most of the Lesser Sunda Islands are located within the Wallacea region, except for the Bali province which is west of the Wallace Line and is within the Sunda Shelf. Together with the Greater Sunda Islands to the west they make up the Sunda Islands. The islands are part of a volcanic arc, the Sunda Arc, formed by subduction along the Sunda Trench in the Java Sea. Slightly over 20 million people live on the islands. Etymologically, Nusa Tenggara means "Southeast Islands" from the words of nusa which means 'island' from Old Javanese language and tenggara means 'southeast'.
The geology of Seychelles is an example of a felsic granite microcontinent that broke off from the supercontinent Gondwana within the past 145 million years and become isolated in the Indian Ocean. The islands are primarily granite rock, with some sequences of sedimentary rocks formed during rift basin periods or times when the islands were submerged in shallow water.