The African Plate
is a major tectonic plate
straddling the Equator
as well as the prime meridian
. It includes much of the continent
, 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
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.
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.
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)[clarify]
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.
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.
- ^ "Sizes of Tectonic or Lithospheric Plates". About.com. Retrieved 30 June 2015.
- ^ "Somali Plate". Ashten Sawitsky. Retrieved 30 June 2015.
- ^ 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. S2CID 4403043.
- ^ Huang, Zhen Shao (1997). "Speed of the Continental Plates". The Physics Factbook. Retrieved 7 June 2018.
- ^ 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.
Last edited on 5 May 2021, at 18:17
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