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.[2] 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.[3]

African Plate
The African Plate
TypeMajor
Approximate area61,300,000 km2 (23,700,000 sq mi)[1]
FeaturesAfrica, Atlantic Ocean, Mediterranean Sea

Boundaries

The western edge of the African Plate is a divergent boundary with the North American Plate to the north and the South American Plate to the south which forms the central and southern part of the Mid-Atlantic Ridge. The African Plate is bounded on the northeast by the Arabian Plate, the southeast by the Somali Plate, the north by the Eurasian Plate, the Aegean Sea Plate, and the Anatolian Plate, and on the south by the Antarctic Plate. All of these are divergent or spreading boundaries with the exception of the northern boundary and a short segment near the Azores known as the Terceira Rift.

Components

The African Plate includes several cratons, stable blocks of old crust with deep roots in the subcontinental lithospheric mantle, and less stable terranes, which came together to form the African continent during the assembly of the supercontinent Pangea around 250 million years ago. The cratons are, from south to north, the Kalahari Craton, Congo Craton, Tanzania Craton and West African Craton. The cratons were widely separated in the past, but came together during the Pan-African orogeny and stayed together when Gondwana split up. The cratons are connected by orogenic belts, regions of highly deformed rock where the tectonic plates have engaged. The Saharan Metacraton has been tentatively identified as the remains of a craton that has become detached from the subcontinental lithospheric mantle, but alternatively may consist of a collection of unrelated crustal fragments swept together during the Pan-African orogeny.

In some areas, the cratons are covered by sedimentary basins, such as the Tindouf Basin, Taoudeni Basin and Congo Basin, where the underlying archaic crust is overlaid by more recent Neoproterozoic sediments. The plate includes shear zones such as the Central African Shear Zone (CASZ) where, in the past, two sections of the crust were moving in opposite directions, and rifts such as the Anza Trough where the crust was pulled apart, and the resulting depression filled with more modern sediment.

Modern movements

Motion of Nubia Plate
Today, the African Plate is moving over Earth's surface at a speed of 0.292° ± 0.007° per million years, relative to the "average" Earth (NNR-MORVEL56)
EAfrica
Map of East Africa showing some of the historically active volcanoes(red triangles) and the Afar Triangle (shaded, center) – a triple junction where three plates are pulling away from one another: the Arabian Plate, the African Plate, and the Somali Plate (USGS).

The African Plate is rifting in the eastern interior of the African continent along the East African Rift. This rift zone separates the African Plate to the west from the Somali Plate to the east. One hypothesis proposes the existence of a mantle plume beneath the Afar region, whereas an opposing hypothesis asserts that the rifting is merely a zone of maximum weakness where the African Plate is deforming as plates to its east are moving rapidly northward.

The African Plate's speed is estimated at around 2.15 cm (0.85 in) per year.[4] It has been moving over the past 100 million years or so in a general northeast direction. This is drawing it closer to the Eurasian Plate, causing subduction where oceanic crust is converging with continental crust (e.g. portions of the central and eastern Mediterranean). In the western Mediterranean, the relative motions of the Eurasian and African plates produce a combination of lateral and compressive forces, concentrated in a zone known as the Azores–Gibraltar Fault Zone. Along its northeast margin, the African Plate is bounded by the Red Sea Rift where the Arabian Plate is moving away from the African Plate.

The New England hotspot in the Atlantic Ocean has probably created a short line of mid- to late-Tertiary age seamounts on the African Plate but appears to be currently inactive.[5]

References

  1. ^ "Sizes of Tectonic or Lithospheric Plates". About.com. Retrieved 30 June 2015.
  2. ^ "Somali Plate". Ashten Sawitsky. Retrieved 30 June 2015.
  3. ^ Chu, D.; Gordon, R.G. (1999). "Evidence for motion between Nubia and Somalia along the Southwest Indian ridge". Nature. 398 (6722): 64–67. Bibcode:1999Natur.398...64C. doi:10.1038/18014. Retrieved 20 June 2015.
  4. ^ Huang, Zhen Shao (1997). "Speed of the Continental Plates". The Physics Factbook. Retrieved 7 June 2018.
  5. ^ Duncan, R.A. (1984). "Age progressive volcanism in the New England Seamounts and the opening of the central Atlantic Ocean". Journal of Geophysical Research: Solid Earth. 89 (B12): 9980–90. Bibcode:1984JGR....89.9980D. doi:10.1029/jb089ib12p09980.

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Adriatic Plate

The Adriatic or Apulian Plate is a small tectonic plate carrying primarily continental crust that broke away from the African plate along a large transform fault in the Cretaceous period. The name Adriatic Plate is usually used when referring to the northern part of the plate. This part of the plate was deformed during the Alpine orogeny, when the Adriatic/Apulian Plate collided with the Eurasian plate.

The Adriatic/Apulian Plate is thought to still move independently of the Eurasian Plate in NNE direction with a small component of counter-clockwise rotation. The fault zone that separates the two is the Periadriatic Seam that runs through the Alps. Studies indicate that in addition to deforming, the Eurasian continental crust has actually subducted to some extent below the Adriatic/Apulian Plate, an unusual circumstance in plate tectonics. Oceanic crust of the African Plate is also subducting under the Adriatic/Apulian Plate off the western and southern coasts of the Italian Peninsula, creating a berm of assorted debris which rises from the seafloor and continues onshore. This subduction is also responsible for the volcanics of southern Italy.

The eastern Italian Peninsula, the coastal part of Slovenia, Istria, Malta and the Adriatic Sea are on the Adriatic/Apulian Plate. Mesozoic sedimentary rocks deposited on the plate include the limestones that form the Southern Calcareous Alps.

Aegean Sea Plate

The Aegean Sea Plate (also called the Hellenic Plate or Aegean Plate) is a small tectonic plate located in the eastern Mediterranean Sea under southern Greece and far western Turkey. Its southern edge is a subduction zone south of Crete, where the African Plate is being swept under the Aegean Sea Plate. To the north is the Eurasian Plate, which is a divergent boundary responsible for the formation of the Gulf of Corinth.

Agulhas Basin

The Agulhas Basin is an oceanic basin located south of South Africa where the South Atlantic Ocean and south-western Indian Ocean meet. Part of the African Plate, it is bounded by the Agulhas Ridge (part of the Agulhas-Falkland Fracture Zone) to the north and the Southwest Indian Ridge to the south; by the Meteor Rise to the west and the Agulhas Plateau to the east. Numerous bathymetric anomalies hint at the basin's dynamic tectonic history.

Aleppo plateau

Aleppo plateau (Arabic: هضبة حلب‎ [ˈhædˤabæt ˈħælæb]) is a low, gently undulating plateau of northern Syria. It lies at the northern end of the junction between the Arabian Plate and the African Plate at the Dead Sea Rift. The plateau lies mostly in the Aleppo Governorate and Idlib Governorate. Aleppo is located in the north-center of the plateau.

Alpine orogeny

The Alpine orogeny or Alpide orogeny is an orogenic phase in the Late Mesozoic (Eoalpine) and the current Cenozoic that has formed the mountain ranges of the Alpide belt. These mountains include (from west to east) the Atlas, the Rif, the Baetic Cordillera, the Cantabrian Mountains, the Pyrenees, the Alps, the Apennine Mountains, the Dinaric Alps, the Pindus (Hellenides), the Carpathians, the Balkanides - Balkan Mountains and Rila-Rhodope massifs, the Pontic Mountains, the Taurus, the Armenian Highlands, the Caucasus, the Alborz, the Zagros, the Hindu Kush, the Pamir, the Karakoram, and the Himalayas. Sometimes other names occur to describe the formation of separate mountain ranges: for example Carpathian orogeny for the Carpathians, Hellenic orogeny for the Pindus, Altai orogeny for Altai Mountains or the Himalayan orogeny for the Himalayas.

The Alpine orogeny has also led to the formation of more distant and smaller geological features such as the Weald–Artois Anticline in southern England and northern France, the remains of which can be seen in the chalk ridges of the North and South Downs in southern England. Its effects are particularly visible on the Isle of Wight, where the Chalk Group and overlying Eocene strata are folded to near-vertical, as seen in exposures at Alum Bay and Whitecliff Bay, and on the Dorset coast near Lulworth Cove. Stresses arising from the Alpine orogeny caused the Cenozoic uplift of the Sudetes mountain range and possibly faulted rocks as far away as Öland in southern Sweden during the Paleocene.The Alpine orogeny is caused by the continents Africa and India and the small Cimmerian plate colliding (from the south) with Eurasia in the north. Convergent movements between the tectonic plates (the Indian plate and the African plate from the south, the Eurasian plate from the north, and many smaller plates and microplates) had already begun in the early Cretaceous, but the major phases of mountain building began in the Paleocene to Eocene. The process continues currently in some of the Alpide mountain ranges.

The Alpine orogeny is considered one of the three major phases of orogeny in Europe that define the geology of that continent, along with the Caledonian orogeny that formed the Old Red Sandstone Continent when the continents Baltica and Laurentia collided in the early Paleozoic, and the Hercynian or Variscan orogeny that formed Pangaea when Gondwana and the Old Red Sandstone Continent collided in the middle to late Paleozoic.

Anatolian Plate

The Anatolian Plate or the Turkish Plate is a continental tectonic plate comprising most of the Anatolia (Asia Minor) peninsula (and the country of Turkey).

To the east, the East Anatolian Fault, a left lateral transform fault, forms a boundary with the Arabian Plate. To the south and southwest is a convergent boundary with the African Plate. This convergence manifests in compressive features within the oceanic crust beneath the Mediterranean as well as within the continental crust of Anatolia itself, and also by what are generally considered to be subduction zones along the Hellenic and Cyprus arcs.

The northern edge is a transform boundary with the Eurasian Plate, forming the North Anatolian Fault Zone (NAFZ).

Research indicates that the Anatolian Plate is rotating counterclockwise as it is being pushed west by the Arabian Plate, impeded from any northerly movement by the Eurasian Plate. In some references, the Anatolian Plate is referred to as a "block" of continental crust still coupled to the Eurasian Plate. But studies of the North Anatolian Fault indicate that Anatolia is de-coupled from the Eurasian Plate. It is now being squeezed by the Arabian Plate from the east and forced toward the west as the Eurasian Plate to its north is blocking motion in that direction. The African Plate is subducting beneath the Anatolian Plate along the Cyprus and Hellenic Arcs offshore in the Mediterranean Sea.

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

Arabian Plate

The Arabian Plate is a tectonic plate in the northern and eastern hemispheres.

It is one of three continental plates (the African, Arabian, and Indian Plates) that have been moving northward in recent geological history and colliding with the Eurasian Plate. This is resulting in a mingling of plate pieces and mountain ranges extending in the west from the Pyrenees, crossing Southern Europe to Iran, forming the Alborz and Zagros Mountains, to the Himalayas and ranges of Southeast Asia.

Eurasian Plate

The Eurasian Plate is a tectonic plate which 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 the area east of the Chersky Range in East Siberia. It also includes oceanic crust extending westward to the Mid-Atlantic Ridge and northward to the Gakkel Ridge.

The eastern side is a boundary with the North American Plate to the north and a boundary with the Philippine Sea Plate to the south and possibly with the Okhotsk Plate and the Amurian Plate. The southerly side is a boundary with the African Plate to the west, the Arabian Plate in the middle and the Indo-Australian Plate to the east. The westerly side is a divergent boundary with the North American Plate forming the northernmost part of the Mid-Atlantic Ridge, which is straddled by Iceland. All of the volcanic eruptions in Iceland, such as the 1973 eruption of Eldfell, the 1783 eruption of Laki, and the 2010 eruption of Eyjafjallajökull, are caused by the North American and the Eurasian Plates moving apart, which is a result of divergent plate boundary forces.

The geodynamics of central Asia is dominated by the interaction between the Eurasian and Indian Plates. In this area, many subplates or crust blocks have been recognized, which form the Central Asian and the East Asian transit zones.

Farmakas

Farmakas (Greek: Φαρμακάς) is a village in the Nicosia District of Cyprus, located around 5 km east of Palaichori Oreinis.

It is a fragment of a fully developed oceanic crust, consisting of plutonic, intrusive and volcanic rocks and chemical sediments. The stratigraphic completeness of the ophiolite makes it unique. It was created during the complex process of sea-floor spreading and formation of oceanic crust and was emerged and placed in its present position through complicated tectonic processes related to the collision of the Eurasian plate to the north and the African plate to the south.

The Troodos Ophiolite has a very significant role for the water budget of the island. Most of the rocks, especially the gabbros and the sheeted dykes are good aquifers due to fracturing. The perennial rivers running radially are feeding the main aquifers in the periphery of the Troodos and the plains.

Geology of Europe

The geology of Europe is varied and complex, and gives rise to the wide variety of landscapes found across the continent, from the Scottish Highlands to the rolling plains of Hungary. Europe's most significant feature is the dichotomy between highland and mountainous Southern Europe and a vast, partially underwater, northern plain ranging from England in the west to the Ural Mountains in the east. These two halves are separated by the Pyrenees and the Alps-Carpathians mountain chain. The northern plains are delimited in the west by the Scandinavian Mountains and the mountainous parts of the British Isles. The southern mountainous region is bounded by the Mediterranean Sea and the Black Sea. Major shallow water bodies submerging parts of the northern plains are the Celtic Sea, the North Sea, the Baltic Sea and the Barents Sea.

From the standpoint of plate tectonics, the ongoing northward drive of the African plate into the Eurasian plate in the Mediterranean basin is the most prominent aspect of the European scene today. The pressure exerted by the African plate is the overall cause of the rise of the Pyrenees, the Alps and the Carpathian mountains. Limestones and other sediments, the ancient floor of the Tethys Sea, are pushed high and now make up much of these ranges. A submarine back-arc basin develops south of Italy, which is one of several Mediterranean mini-continental fragments caught between the two plates. This buckling of the Earth's crust forces up Italy's mountains and stimulates active faults and volcanoes such as Mount Etna. Iberia, another separate terrain unit, has been rotated and emplaced against the rest of Europe by the plate collision.

Moving north from the Alps and other ranges, tectonic activity largely fades away in the stable Baltic craton. One exception to this trend is a hot spot, rising from the mantle underneath central Germany, which has been responsible in geologic time for volcanoes such as the Vogelsberg in Hesse and currently provides heat to hot springs and lakes in the region.

Weathering mantles made up of saprolite are common in Europe. Saprolite composition varies from kaolinitic and ferrallitic to grus. The first were formed in the Mesozoic and early Cenozoic while the latter in the late Cenozoic. Stripping of weathered rock has produced depressions occupied by numerous lakes in Finland and Sweden.

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.

Macaronesia

Macaronesia is a collection of four archipelagos in the North Atlantic Ocean off the coast of the continents of Europe and Africa. Each archipelago is made up of a number of Atlantic oceanic islands formed by seamounts on the ocean floor with peaks above the ocean's surface. The Macaronesian islands belong to three countries: Portugal, Spain, and Cape Verde. Politically, the islands belonging to Portugal and Spain are part of the European Union. Geologically, Macaronesia is part of the African Plate, including the Azores, which mark its edge at the meeting point with the Eurasian and American Plates.The European Union considers that the three European archipelagos (i.e. not including Cape Verde) conform a unique biogeographical region called the Macaronesian Region.

Madagascar Plate

The Madagascar Plate or Madagascar block was once attached to the Gondwana supercontinent and later the Indo-Australian Plate.

Rifting in the Somali Basin began at the end of the Carboniferous 300 million years ago, as a part of the Karoo rift system. The initiation of Gondwana breakup, and transform faulting along the Davie Fracture Zone, occurred in the Toarcian (about 182 million years ago) following the eruption of the Bouvet (Karoo) mantle plume. At this time East Gondwana, comprising the Antarctic, Madagascar, Indian, and Australian plates, began to separate from the African Plate. East Gondwana then began to break apart about 115–120 million years ago when India began to move northward. Between 84–95 million years ago rifting separated Seychelles and India from Madagascar.

Since its formation the Madagascar block has moved roughly in conjunction with Africa, and thus there are questions as to whether the Madagascar Plate should be still considered a separate plate.

New England hotspot

The New England hotspot, also referred to as the Great Meteor hotspot, is a long-lived volcanic hotspot in the Atlantic Ocean. The hotspot's most recent eruptive center is the Great Meteor Seamount, and it probably created a short line of mid to late-Cenozoic age seamounts on the African Plate but appears to be currently inactive.The New England hotspot track is used to estimate the movement of the North American Plate away from the African Plate from early Cretaceous period to the present.The New England hotspot has been overridden by the Mid-Atlantic Ridge.

Red Sea Rift

The Red Sea Rift is a spreading center between two tectonic plates, the African Plate and the Arabian Plate. It extends from the Dead Sea Transform fault system, and ends at an intersection with the Aden Ridge and the East African Rift, forming the Afar Triple Junction in the Afar Depression of the Horn of Africa.

The Red Sea Rift was formed by the divergence between the African Plate and the Arabian Plate. The rift transitioned from a continental rift to an oceanic rift. Magnetic anomalies suggest that the spreading rate on either side of the Red Sea is about 1 cm/year. The African plate has a rotation rate of 0.9270 degrees/Ma, while the Arabian plate has a rotation rate of 1.1616 degrees/Ma.

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.

South American Plate

The South American Plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African Plate, with which it forms the southern part of the Mid-Atlantic Ridge.

The easterly edge is a divergent boundary with the African Plate; the southerly edge is a complex boundary with the Antarctic Plate, the Scotia Plate, and the Sandwich Plate; the westerly edge is a convergent boundary with the subducting Nazca Plate; and the northerly edge is a boundary with the Caribbean Plate and the oceanic crust of the North American Plate. At the Chile Triple Junction, near the west coast of the Taitao–Tres Montes Peninsula, an oceanic ridge known as the Chile Rise is actively subducting under the South American Plate.

Geological research suggests that the South American Plate is moving westward away from the Mid-Atlantic Ridge: "Parts of the plate boundaries consisting of alternations of relatively short transform fault and spreading ridge segments are represented by a boundary following the general trend." As a result, the eastward-moving and more dense Nazca Plate is subducting under the western edge of the South American Plate, along the continent's Pacific coast, at a rate of 77 mm (3.0 in) per year. The collision of these two plates is responsible for lifting the massive Andes Mountains and for creating the numerous volcanoes which are strewn throughout them.

Volcanology of Italy

Italy is a volcanically active country, containing the only active volcanoes in mainland Europe. The country's volcanism is due chiefly to the presence, a short distance to the south, of the boundary between the Eurasian Plate and the African Plate. The magma erupted by Italy's volcanoes is thought to result from the subduction and melting of one plate below another.

Three main clusters of volcanism exist: a line of volcanic centres running northwest along the central part of the Italian mainland (see: Campanian volcanic arc); a cluster in the northeast of Sicily; and another cluster around the Mediterranean island of Pantelleria.

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

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