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The African continent consists of five old bedrock areas, cratons, which are
welded together with younger mountain chains. 57 percent of the continent
has exposed Precambrian rocks to the surface, and the rest has younger deposits
on this bedrock. Africa took its present form when South
America, Antarctica and Australia disassociated themselves from the great Gondwana continent
less than 200 million years ago.
Archaic bedrock (2.5 billion years and older)
The oldest bedrock in Africa is the so-called granite-gneiss-greenstone belts
in the Kaapvaal, Zimbabwe and Congo cratons. See all countries in the continents
of Africa on
Countryaah. They date from up to 3.6 billion
years ago. In the greenstone belts, the volcanic rock has comatite as a
particularly characteristic rock. This rock is originally a lava formed on the
seabed. After a period of throngs of huge volumes of granite towards the end of
the archaeological and tectonic stabilization, the area was worn down and
covered with sandstones, which contain economically important gold and uranium
deposits, including at Witwatersrand in South Africa. In silica slate(chert)
from greenstone belts in the Transvaal, fossils of unicellular algae have been
found, which is one of the oldest traces of life known in the world.
Proterozoic bedrock (from 2.5 billion to about 545 million years old)
At the end of the Precambrian 950–550 million years ago, several elongated
fold belts were formed (Pan-African episode). Towards the end of
the Precambrian, large, wide recesses formed, which were filled with sedimentary
and volcanic deposits, including in the Transvaal, Congo and West Africa basins.
The Transvaal contains economically important iron ore, and the West African
basin contains moraine conglomerate, confidence, which points to an ice age in
this area at the end of the Precambrian (as in Norway).
Younger bedrock
Between 545 and 248 million years ago, smaller folding belts were built,
including in South Africa (Cape Belt), Morocco ( Anti-Atlas Belt ) and
Mauritania (Mauritania Belt). These correspond to the Caledonian and Hercynian
mountain range folds in Europe.
200–300 million years ago, huge floods of the volcanic rock
erupted basally in South Africa, Namibia and East Africa ( Karroo basalts). These
large column eruptions are likely to be related to the beginning of the Great Gondwana continent. In Cretaceous,
very special and yet little understood volcanic phenomena took place, producing
diamond-bearing kimberlite pipes in central and southern Africa.
100 to 40 million years ago, northwestern parts of the continent took part
in the alpine mountain range folding, which resulted from a clash between the
African and European plates. This provided the Atlas Mountains, which are part
of the alpine folding zone. In the east, the Red Sea opened during
a tertiary along a rift between the African and Arab land masses. A similar rift
has now formed through East Africa ( East African rift system or "graben")
from Lake Malawi in the south, through East Africa to Ethiopia and on to the
Jordan Valley. Today there is active volcanism (including
the Kilimanjaro volcano, among others), which is the continent's
highest mountain, 5895 meters above sea level. and Mt. Kenya, 5199 meter asl). If
this rift zone continues to burst, one must wait for the sea to penetrate and
the eastern part to become an island. What one sees by the Red Sea and the East
African Rift system are probably early stages in the formation of the world sea.
Africa - wildlife
The wildlife of North Africa is similar to that of Europe and northern Asia.
Here are deer, steelworms and bumblebees - animal groups that are missing from
sub-Saharan Africa. The area is considered the Palarctic region.
The rest of the continent has a distinctive fauna and, together with
Madagascar, constitutes the Afrotropical region, which is best known
for its many large mammals: African elephant, white and black rhino,
hippopotamus, lion, zebra, giraffe, coffee buffalo and not least the numerous
species of antelopes. Africa is the continent with the largest species of large
ungulates. The region is also characterized by a large number of mammalian
families that are not found anywhere else, such as octopus mice, golden moles
and ground pigs. The bird fauna is not unique, although there are some endemic
families, such as mouse birds and banana eaters. African bird life is
characterized by winter influx of migratory birds from the north. In South
Africa, penguins live. Among the reptiles, especially crocodile and the product
are conspicuous, but there are also many snake species, among others. a. Several
toxic species such as mamba, cobra and viper.
Among the approx. 2,000 species of freshwater fish are found in old groups of
bony fish: bikir, bald eagle and African lungfish. The large species richness of
cichlids in i.a. Lake Victoria, Tanzania and Malawi are also notable. In each
lake there are up to several hundred closely related species, but each with
their distinctive habitat.
Wildlife in the African rainforests is not as rich as in South American and
Southeast Asian. The savannah, in turn, houses a very species-rich fauna, which
among other things. includes most wild game species that attract tourists and
hunters.
In the desert areas there is a relatively species-rich wildlife; in
particular, the Namib Desert is home to a wealth of specially adapted insects
and other invertebrates. Sahara wildlife is more species poor, which is probably
related to the relatively young age of the desert.
The Afrotropical fauna has many features in common with the tropical Asian
fauna (eg elephants and rhinos). However, certain African animal groups (eg
carpal salmon) have their closest relatives in tropical Central and South
America. In the southernmost part of Africa, some groups of invertebrates are
closely related to species from New Zealand, Australia and southern South
America. This pattern of propagation is interpreted as the result of continental
drift caused by plate tectonics.
Madagascar belongs geographically to Africa, but the island's wildlife is
very different from African and is described under Madagascar.
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