Ngorongoro Crater contains one of the most magnificent wildlife reserves in Africa.

This volcanic crater is home to about 25,000 large mammals.

Formation of Ngorongoro Crater

Ngorongoro is one of many extinct volcanoes in east Africa's Crater Highland region. These volcanoes first erupted around 25 million years ago, at a time when the Great Rift Valley, which runs for 6,500km (4,060mi) from the Zambesi River in the south to Syria in the north, was also being formed.

An extensive upheaval in the Earth's crust was caused when two of its immense sections, or tectonic plates, began to move apart in a process known as continental drift. East Africa resides on one of the plates, while the remainder of the continent rests on the other.

As the two tectonic plates drew apart, a rift opened up in the Earth's crust, allowing molten rock, or magma, to escape from the Earth's core.

This fiery liquid burst through the cones of Ngorongoro and other volcanoes, showering the surrounding plains with lava and dust. After the eruption, a large lake of molten rock is thought to have formed beneath Ngorongoro but close to its surface.

Around 2.5 million years ago, additional disturbances in the underlying rock structure caused this magma lake to drain, leaving Ngorongoro poised above a huge underground cavity. At this time, the volcano's peak was an estimated 4,570m (15,000ft) above sea level, a similar height to the present-day Mount Kilimanjaro, some 208km (130mi) to the east.

Eventually, the weight of rock, combined with fresh eruptions, caused the volcano to collapse inward, leaving behind an enormous crater - or, more properly, a caldera.

The floor of the Ngorongoro crater, which covers an area of about (100sq.mi), lies 610m (2,000ft) below the rim and about 1,830m (6,000ft) above sea level. Round Table Hill, a low, flat-topped hill to the northwest of Ngorongoro's plain, is thought to be the remains of the volcano's peak. The flat basin, which is roughly circular with a diameter of about 16km (10mi), contains grasslands typical of east Africa's savanna.

Animals of Ngorongoro Crater

Unlike the Serengeti Plain to the west, where more than two million animals must migrate when the wet season is over, the Ngorongoro is blessed with an almost continuous supply of water. This natural irrigation maintains the habitat through the year and prevents the herbivorous animals seeking grazing lands beyond the crater's rim.

In the dry season, the eastern Serengeti is almost deserted whereas the animal population of Ngorongoro rarely falls below 80 per cent of its maximum. Animals leaving the crater often do so at night via ancient trails forged by their predecessors

Two rivers, the Munge and the Lonyokie, supply the crater with water. They feed swamps along their course and eventually flow into the glittering blue waters of a soda lake.

This lake lies at the lowest point of the crater but has no outlet.

Evaporation tends to leave its waters brackish and, because of this, the aquatic life is restricted - a contrast to other east African lakes, which are rich in wildlife. Lake Tanganyika, for example, contains more species of fish than any other lake in the world.

Huge flocks of flamingoes wade through the shallow waters like a moving pink carpet. At the slightest hint of danger, the flocks take to the air and circle majestically before returning to the lake.

Two distinct flamingo species feed in the warm waters. The lesser flamingo, the smaller of the two, feeds on microscopic green algae that live in the surface waters of the lake. The fine filtering mechanism in the bird's beak strains the water and collects the algae. Lesser flamingoes feed all day long, filtering around 30 liters (6.6 gallons) of water an hour.

The greater flamingo has a coarser filtering mechanism in its beak, which enables it to sift through the mud and sediment on the lakebed for crustaceans, small fish and organic detritus.

Not only do the two flamingoes eat different food, they occupy different parts of the lake. The greater flamingo is restricted to the shore where it can reach the mud; the lesser flamingo filter feeds while walking or swimming throughout the whole expanse of the lake.

Munge Swamp to the north of the lake provides a permanent waterhole for hippos and elephants, while during the dry season much of Ngorongoro's wildlife congregates here.

As herbivores, such as zebra, wildebeest and gazelles, drink and graze, they are forever on the alert. Their camouflage is only a temporary measure: the black and white stripes of the zebra (break up its outline; the brindled coat of the wildebeest matches the browns of the dry savanna.

The floor of Ngorongoro crater has almost no obstacles. This creates an ideal environment for hyenas, which need open space for running and hunting in packs. Lions are more stealthy hunters, and have difficulty hunting out in the open, with no trees or rocks to hide behind. Thus, they depend on the hyenas to do the hunting for them.