The open plains of the eastern Serengeti rise to the crater highlands of the volcanic massifs of Loolmalasin (3,587 m) and Oldeani (3,168 m) dating from the late Mesozoic and early Tertiary.
Ngorongoro Crater is one of the largest inactive unbroken calderas in the world which is unflooded. It has a mean diameter of 16-19 km, a crater floor of 26,400 ha, and a rim soaring to 400-610 m above the crater floor. The formation of the crater and other highlands are associated with the massive rifting which occurred to the west of the Gregory Rift Valley. The conservation area also includes Empakaai Crater and Olduvai Gorge, famous for geology and associated paleontological studies.
A variable climate and diverse landforms and altitudes have resulted in several distinct habitats. Scrub heath and the remains of dense alpine forests cover the steep slopes. The crater floor is mainly open grassy plains with alternating fresh and brackish water lakes, swamps and two patches of acacia woodland; Lerai Forest, comprising dominant tree species Acacia xanthonhloea and Rauvolfia caffra.
A population of about 25,000 large animals lives in the crater, mainly ungulates, along with the highest density of mammalian predators in Africa. They include the critically endangered black rhinoceros Diceros bicornis , which have declined from about 108 in 1964-66 to between 11-14 in 1995, and hippopotamus, which are very uncommon in the area. There are also many other ungulates: wildebeest (7,000 estimated in 1994), Burchell’s zebra (4,000), eland, Grant’s and Thomson’s gazelles (3,000). The crater has the densest known population of lion, which are classed as vulnerable, numbering only 62 in 2001. On the crater rim are leopard and the endangered African elephant, numbering 42 in 1987 but only 29 in 1992, mountain reedbuck and buffalo (4,000 in 1994). However, since the 1980s the crater’s wildebeest population has fallen by a quarter to about 19,000 and the numbers of eland and Thomson’s gazelle have also declined whereas buffalos increased greatly, probably due to the prevention of fire which favours high fibrous grasses over shorter, less fibrous types.
In summer enormous numbers of Serengeti migrants pass through the plains of the reserve, including 1.7 million wildebeest, 260,000 zebra and 470,000 gazelle. Waterbuck mainly occur mainly near Lerai Forest; serval widely in the crater and on the plains to the west. Common in the reserve are lion, hartebeest, spotted hyena and jackal. Cheetah, classed as vulnerable although common in the reserve, are scarce in the crater itself. The endangered wild dog Lycaon pictus has recently disappeared from the crater and may have declined elsewhere in the Conservation Area as well. The golden cat has recently been seen in the Ngorongoro forest.
Ngorongoro has paleontological and archaeological sites over a wide range of dates. The four major sites are Olduvai Gorge, Laetoli site, Lake Ndutu site and the Nasera Rock Shelter. The variety and richness of the fossil remains, including those of early hominids, has made this one of the major areas in the world for research on the human evolution. Olduvai Gorge has produced valuable remains of early hominids including Australopithecus and Homo habilis as well as fossil bones of many extinct animals. Nearby, at Laetoli, are fossil hominid footprints from the Pliocene age.
Actually there is considerable controversy about the exact number of people in the NCA partly because pastoral people, being mobile, are difficult to enumerate. The property provides grazing land for semi-nomadic Maasai pastoralists. At the time of inscription at Unesco an estimated 20,000 Maasai were living in the property, with some 275,000 head of livestock, which was considered within the capacity of the reserve. No permanent agriculture is officially allowed in the property. Further growth of the Maasai population and the number of cattle should remain within the capacity of the property, and increasing sedentarisation, local overgrazing and agricultural encroachment are threats to both the natural and cultural values of the property. There were no inhabitants in Ngorongoro and Empaakai Craters or the forest at the time of inscription in 1979.