Somali Plate

The Somali Plate is a minor tectonic plate, which straddles the equator in the eastern hemisphere. It is approximately centered on the island of Madagascar and includes about half of the East coast of Africa, from the Gulf of Aden in the North through the East African Rift Valley. The southern boundary with the Nubian-African Plate is a diffuse plate boundary consisting of the Lwandle Plate.[2]

Somali Plate
The Somali Plate
TypeMinor
Approximate area16,700,000 km2[1]
Movement1south-east
Speed16 mm/year
FeaturesEast Africa, Madagascar, Indian Ocean
1Relative to the African Plate

Geology

The Arabian Plate diverges to the north forming the Gulf of Aden. The Indian Plate, Australian Plate, and Antarctic Plate all diverge from the Somali Plate forming the eastern Indian Ocean. The Somali-Indian boundary spreading ridge is known as the Carlsberg Ridge. The Somali-Australian boundary spreading ridge is known as the Central Indian Ridge. The Somali-Antarctic boundary spreading ridge is known as the Southwest Indian Ridge. The western boundary with the African Plate is diverging to form the East African Rift, which stretches south from the triple junction in the Afar depression. The southern boundary with the Nubian-African Plate is a diffuse plate boundary with of the Lwandle Plate.[2] The Seychelles and the Mascarene Plateau are located northeast of the Madagascar.

Tectonic history

From 1.4 to 1.2 Ga the Kibaran orogeny fused the Tanzanian and Congo cratons.[3] From 1000 to 600 Ma the super-continent Gondwana was formed and the Pan-African orogeny sutured the Tanzanian and Kalahari cratons.[3] The rifting of Gondwana occurred from 190 Ma to 47 Ma separating Madagascar from the eastern coast of Africa and placing the Seychelles/Mascarene Plateau northeast of Madagascar.[4][5] The rifting of the Red Sea started around 30 million years ago and the first rifting occurred in the northern East African Rift System around 20 million years ago.[6]

References

  1. ^ Alden, Andrew (2017-03-17) Here Are the Sizes of Tectonic or Lithospheric Plates. thoughtco.com
  2. ^ a b Saria, E (20 March 2014). "Present-day Kinematics of the East African Rift". JGR Solid Earth. 119 (4): 3584–3600. doi:10.1002/2013JB010901.
  3. ^ a b Rogers, J; Santosh, M (2004). Continents and supercontinents (PDF). Oxford: Oxford University Press. p. 723. ISBN 9780195165890.
  4. ^ Ali, J; Aitchison, C (2008). "Gondwana to Asia: Plate tectonics, paleogeography and the biological connectivity of the Indian sub-continent from the Middle Jurassic through latest Eocene (166–35 Ma)". Earth-Science Reviews. 88 (3–4): 145–166. doi:10.1016/j.earscirev.2008.01.007.
  5. ^ Plummer, P (1995). "Ages and geological significance of the igneous rocks from Seychelles". Journal of African Earth Sciences. 20 (2): 91–101. Bibcode:1995JAfES..20...91P. doi:10.1016/0899-5362(95)00035-R.
  6. ^ Chorowicz, Jean (October 2005). "The East African rift system". Journal of African Earth Sciences. 43 (1–3): 379–410. Bibcode:2005JAfES..43..379C. doi:10.1016/j.jafrearsci.2005.07.019.

Further reading

Addis Ababa

Addis Ababa (Amharic: አዲስ አበባ, Addis Abäba IPA: [adˈdis ˈabəba] (listen), "new flower") or Addis Abeba, also known as Finfinne (Oromo: Finfinne "natural spring"), is the capital and largest city of Ethiopia. According to the 2007 census, the city has a population of 2,739,551 inhabitants.As a chartered city, Addis Ababa also serves as a capital city of Oromia. It is where the African Union is headquartered and where its predecessor the Organisation of African Unity (OAU) was based. It also hosts the headquarters of the United Nations Economic Commission for Africa (ECA), as well as various other continental and international organizations. Addis Ababa is therefore often referred to as "the political capital of Africa" for its historical, diplomatic and political significance for the continent. The city lies a few miles west of the East African Rift which splits Ethiopia into two, through the Nubian Plate and the Somali Plate.The city is populated by people from different regions of Ethiopia. It is home to Addis Ababa University.

African Plate

The African Plate is a major tectonic plate straddling the equator as well as the prime meridian. It includes much of the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges. Between 60 million years ago and 10 million years ago, the Somali Plate began rifting from the African Plate along the East African Rift. Since the continent of Africa consists of crust from both the African and the Somali plates, some literature refers to the African Plate as the Nubian Plate to distinguish it from the continent as a whole.

Antarctic Plate

The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau and extending outward under the surrounding oceans. After breakup from Gondwana (the southern part of the supercontinent Pangea), the Antarctic plate began moving the continent of Antarctica south to its present isolated location causing the continent to develop a much colder climate. The Antarctic Plate is bounded almost entirely by extensional mid-ocean ridge systems. The adjoining plates are the Nazca Plate, the South American Plate, the African Plate, the Somali Plate, the Indo-Australian Plate, the Pacific Plate, and, across a transform boundary, the Scotia Plate.

The Antarctic Plate has an area of about 60,900,000 km2 (23,500,000 sq mi). It is the Earth's fifth-largest plate.

The Antarctic Plate's movement is estimated to be at least 1 cm (0.4 in) per year towards the Atlantic Ocean

East African Rift

The East African Rift (EAR) or East African Rift System (EARS) is an active continental rift zone in East Africa. The EAR began developing around the onset of the Miocene, 22–25 million years ago. In the past it was considered to be part of a larger Great Rift Valley that extended north to Asia Minor.

The rift, a narrow zone, is a developing divergent tectonic plate boundary where the African Plate is in the process of splitting into two tectonic plates, called the Somali Plate and the Nubian Plate, at a rate of 6–7 mm (0.24–0.28 in) annually. As extension continues, lithospheric rupture will occur within 10 million years; the Somali Plate will break off and a new ocean basin will form.

Geography of Madagascar

Madagascar is a large island in the Indian Ocean off the eastern coast of southern Africa, east of Mozambique. It has a total area of 587,040 square kilometres (226,660 sq mi) with 581,540 square kilometres (224,530 sq mi) of land and 5,500 square kilometres (2,100 sq mi) of water. Madagascar is the fourth largest island and the 2nd largest island country in the world. The highest point is Maromokotro, in the Tsaratanana Massif region in the north of the island, at 2,876 metres (9,436 ft). The capital Antananarivo is in the Central Highlands near the centre of the island. It has the 25th largest Exclusive Economic Zone of 1,225,259 km2 (473,075 sq mi). Madagascar is 400 kilometres (250 miles) east of mainland Africa.

Geography of Mauritius

Mauritius is an island of Africa's southeast coast located in the Indian Ocean, east of Madagascar. It is geologically located within the Somali plate.

Geography of Mayotte

Mayotte is an island of volcanic origin in the northernmost Mozambique Channel, about one-half of the way from northern Madagascar to northern Mozambique. Mayotte is part of the Comoro Islands, and like them is the result of a former hot spot, the oldest of the Comoros archipelago, formed about 7.7 mya.Mayotte has an area of 374 square kilometres, and a coastline of length 185.2 km. Its maritime claims are an exclusive economic zone of 200 nautical miles, and a territorial sea of 12 nm.

Geography of Mozambique

The geography of Mozambique consists mostly of coastal lowlands with uplands in its center and high plateaus in the northwest. There are also mountains in the western portion. The country is located on the east coast of southern Africa, directly west of the island of Madagascar. Mozambique has a tropical climate with two seasons, a wet season from October to March and a dry season from April to September.

Geography of Réunion

Réunion is an island in Southern Africa, in the Indian Ocean, east of Madagascar. It is an overseas region of France. The total area of the island is 2,512 km², of which 10 km² is water. The island has a coastline of 207 km. The maritime claims of Réunion include an exclusive economic zone of 200 nautical miles, and a territorial sea of 12 nautical miles (22 km). Reunion is geologically situated in the Somali plate.

Geography of Seychelles

The Seychelles is a small island nation located in the Somali sea northeast of Madagascar and about 835 mi (1,344 km) from Mogadishu, Somalia, its nearest foreign mainland city, while Antsiranana is the nearest foreign city overall. Seychelles lies between approximately 4ºS and 10ºS and 46ºE and 54ºE. The nation is an archipelago of 115 tropical islands, some granite and some coral. the majority of which are small and uninhabited. The landmass is only 452 km2 (175 sq mi), but the islands are spread wide over an Exclusive Economic Zone of 1,336,559 km2 (516,048 sq mi). About 90 percent of the population of 90,000 live on Mahé, 9 percent on Praslin and La Digue. Around a third of the land area is the island of Mahé and a further third the atoll of Aldabra.

There are two distinct regions, the granitic islands, the world's only oceanic islands of granitic rock and the coralline outer islands. The granite islands are the world’s oldest ocean islands, while the outer islands are mainly very young, though the Aldabra group and St Pierre (Farquhar Group) are unusual, raised coral islands that have emerged and submerged several times during their long history, the most recent submergence dating from about 125,000 years ago

Geology of Socotra

The geology of Socotra is part of the national geology of Yemen. Ancient Precambrian metamorphic rocks are intruded by younger igneous rocks, overlain by limestones and other marine sediments that deposited during marine transgression periods in the Cretaceous and the past 66 million years of the Cenozoic. The island is on the Somali Plate, which rifted away from the Arabian mainland within the past 60 million years.

Geology of Somalia

The geology of Somalia is built on more than 700 million year old igneous and metamorphic crystalline basement rock, which outcrops at some places in northern Somalia. These ancient units are covered in thick layers of sedimentary rock formed in the last 200 million years and influenced by the rifting apart of the Somali Plate and the Arabian Plate. The geology of Somaliland, the de facto independent country in northern Somalia, is to some degree better studied than that of Somalia as a whole. Instability related to the Somali Civil War and previous political upheaval has limited geologic research in places while heightening the importance of groundwater resources for vulnerable populations.

Geology of Somaliland

The geology of Somaliland is very closely related to the geology of Somalia. Somaliland is a de facto independent country within the boundaries that the international community recognizes as Somalia. Because it encompasses the former territory of British Somaliland, the region is historically better researched than former Italian Somaliland. Somaliland is built on more than 700 million year old igneous and metamorphic crystalline basement rock.. These ancient units are covered in thick layers of sedimentary rock formed in the last 200 million years and influenced by the rifting apart of the Somali Plate and the Arabian Plate.

Great Rift Valley

The Great Rift Valley is a series of contiguous geographic trenches, approximately 6,000 kilometres (3,700 mi) in total length, that runs from the Beqaa Valley in Lebanon in Asia to Mozambique in southeastern Africa. While the name continues in some usages, it is rarely used in geology as it is considered an imprecise merging of separate though related rift and fault systems.

Today, the term is most often used to refer to the valley of the East African Rift, the divergent plate boundary which extends from the Afar Triple Junction southward across eastern Africa, and is in the process of splitting the African Plate into two new separate plates. Geologists generally refer to these incipient plates as the Nubian Plate and the Somali Plate.

Gregory Rift

The Gregory Rift is the eastern branch of the East African Rift fracture system. The rift is being caused by the separation of the Somali plate from the Nubian plate, driven by a thermal plume. Although the term is sometimes used in the narrow sense of the Kenyan Rift, the larger definition of the Gregory Rift is the set of faults and grabens extending southward from the Gulf of Aden through Ethiopia and Kenya into Northern Tanzania, passing over the local uplifts of the Ethiopian and Kenyan domes.

Ancient fossils of early hominins, the ancestors of humans, have been found in the southern part of the Gregory Rift.

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.

Lwandle Plate

The Lwandle Plate is one of three tectonic microplates, along with the Rovuma Plate and Victoria Plate, that make up the African Plate with the Somali Plate and the Nubian Plate. Its discovery is very recent, so the velocity of the plate is neither well known nor well understood. Many experiments are ongoing to quantify this. The Lwandle Plate lies between 30°E and 50°E, sharing a boundary with the Nubian, Somali, and Antarctic Plates.The Lwandle Plate is largely oceanic, lying off the southeast coast of Africa. It is currently believed that the southern part of Madagascar forms part of the Lwandlean Plate, with one of the plate boundaries cutting through the island.

Rovuma Plate

The Rovuma Plate is one of three tectonic microplates that contribute to the Nubian Plate and the Somali Plate. The other two plates are the Lwandle Plate and the Victoria Plate.

Somali Sea

The Somali Sea is a body of water that borders the eastern coast of Somalia.

Major
Minor
Other
Historical
Major African geological formations
Plates
Cratons and shields
Shear zones
Orogens
Rifts
Sedimentary basins
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