The Kalahari is a featureless, gently undulating, sand-covered plain, which everywhere is 3,000 feet (900 metres) or more above sea level. Bedrock is exposed only in the low but vertical-walled hills, called kopjes, that rarely but conspicuously rise above the general surface. Aside from the kopjes, three surfaces characterize virtually all of the Kalahari: sand sheets, longitudinal dunes, and vleis (pans).

The sand sheets appear to have been formed during the Pleistocene Epoch (1,600,000 to 10,000 years ago), and they have been fixed in place since then. In some areas they appear to have been of fluvial origin, the result of sheet flooding in times of much greater precipitation, but by far the greater part of them were wind-formed. The sheets occupy the eastern part of the Kalahari. Their surface elevation varies only slightly, with relief measured in tens of feet per mile. The depth of the sand there generally exceeds 200 feet. In many areas the sand is red, the result of a thin layer of iron oxide that coats the grains of sand. (sand dune)

The entire western Kalahari is characterized by long chains of dunes, oriented roughly to the north or northwest. The dunes measure at least 1 mile in length, several hundred feet in width, and 20 to 200 feet in height. Each dune is separated from its neighbour by a broad parallel depression locally called a straat (“street,” or “lane”), because each constitutes the easy way to travel.

Vleis, or pans (playa), are the terminal features of desert drainage systems, the “dry lakes” at the end of ephemeral streams. Many are remnant features from an earlier period of greater precipitation. Very little water ever flowed to the sea from the Kalahari. Rather, each stream ended its course in a slightly lower depression from which there was no outlet. There, as the stream dried up, the fine silt particles carried in suspension by the sluggish stream were deposited along with soluble calcium minerals and salts precipitated out of the evaporating water. The results are pans—flat surfaces devoid of vegetation that are gleaming white when dry, hardened by the cementing action of the soluble minerals, and, on occasion, covered by a shallow layer of standing water. Where the salt content is low, pans may become covered with grasses after a rain.

In the southern and central parts of the Kalahari, surface water is found only in small, widely scattered waterholes, and surface drainage is nonexistent. Nearly all of the rain that falls disappears immediately into the deep sand. Some is absorbed by the underlying rock strata; some is drawn to the surface by capillary action and evaporated into the air; and some, lifted from the depths by tree roots, is transpired from leaf surfaces. A small amount, landing on nonsandy surfaces, may flow short distances into pans, but this occurs only immediately after the infrequent rains. In some parts of the central and southern Kalahari, extensive ancient drainage systems have been detected—some on the ground and others by way of aerial photographs. None of these operate today, even in the wettest of years.

In the northern Kalahari an extraordinary drainage system prevails. During the summer heavy rains fall on the uplands of central Angola, far to the northwest of the Kalahari. Large amounts of runoff water feed a number of south-flowing streams, which merge to form the Okavango (Okavango River) and Cuando (Kwando) rivers. The Okavango flows to the southeast and into the northernmost portion of the Kalahari, eventually breaking up into a number of distributary channels and feeding the vast area of swamps in northern Botswana. After an abnormally wet rainy season in Angola, excess water fills the swamps and overflows, filling Lake Ngami (Ngami, Lake) farther to the south, and flows eastward through the Boteti River into Lake Xau and the Makgadikgadi Pans. Similarly, the Cuando River flows south from Angola and partly into a northeastern extension of the same swamps. Thus is created the paradoxical situation of an area with an extensive excess of water in a region chronically short of water.

Soils in the Kalahari are largely based on sand, are reddish in color, and are low in organic material. Chemically, they are relatively alkaline, and they are extremely dry. In and near the pans, the soils tend to be highly calcareous or saline, and frequently they are toxic to most vegetation.

Traditionally, an area was classed as desert if it received less than 10 inches (250 millimetres) of rain annually. A more accurate definition of a desert is a region in which the potential evaporation rate is twice as great as the precipitation. Both of these criteria are applicable to the southwestern half of the Kalahari. The northeastern portion, however, receives much more rainfall and, climatically, cannot qualify as a desert; and yet, it is totally lacking in surface water. Rain drains instantly through the deep sands of the area, which creates a situation of edaphic drought (i.e., soil completely devoid of moisture).

Moisture-bearing air is derived from the Indian Ocean, and precipitation is greatest in the northeast (with a mean annual precipitation of more than 20 inches) and declines toward the southwest (less than 5 inches on the southern fringe of the Kalahari). Precipitation, however, is highly variable. Most of the rain comes as summer thunderstorms, with great variation from place to place and from year to year. Winters are extremely dry: humidity is very low, and no rain falls for six to eight months.

Great ranges in both diurnal and seasonal temperatures are the rule, the result of the Kalahari's relatively high altitude and predominantly clear, dry air (allowing strong insolational heating in daytime and great radiational heat loss at night). As a result, shade temperatures often reach 110°–115° F (43°–46° C) on summer days but drop to 70°–80° F (21°–27° C) on the same nights; temperatures on winter nights commonly drop to freezing and may go as low as 10° F (-12° C).

The presence of a deep sand cover over most of the area greatly affects the vegetation that grows there. Shallow-rooted plants cannot survive on a perennial basis, although annuals that grow very rapidly after a good rain may be able to sow seeds that will endure until the next good rainy season. Trees with roots deep enough to reach permanently moist sand levels do well.

The southwestern Kalahari, with its very low precipitation, has few trees or large bushes—only scattered xerophytic (drought-tolerant) shrubs and short grasses. The central Kalahari, with more rain, has scattered trees (several species of Acacia) and some shrubs and grasses. The northern Kalahari does not have the appearance of a desert at all. It has open woodlands, palm trees growing among thorn brush, and forests of both evergreen and deciduous trees that grow to heights of 50 feet and yield some species suitable for timber; one of the largest and most unusual of these trees is the baobab. The Okavango Swamp supports a dense growth of reeds, papyrus, pond lilies, and other water-loving plants.

The northern Kalahari supports a considerable population of giraffes, zebras, elephants, buffalo, and antelopes (roan, sable, tsessebe, and impala); predators such as lions, cheetahs, leopards, wild hunting dogs, and foxes; other large and medium-sized mammals, such as jackals, hyenas, warthogs, baboons, badgers, anteaters, ant bears, hare, and porcupines; and numerous small rodents, several types of snakes and lizards, and a wealth of birdlife.

The Kalahari is inhabited primarily by Bantu-speaking (Bantu peoples) Africans and Khoisan-speaking San, with a small number of Europeans.

The Bantu-speaking peoples—the Tswana, the Kgalagadi, and the Herero—are relative newcomers to the Kalahari. In the late 18th century the Tswana spread west from the Limpopo basin into the northern and eastern Kalahari; the Kgalagadi moved north and west into the southern and western Kalahari; and the Herero refugees from the German colonial wars in South West Africa (Namibia) fled east into the western and northern Kalahari at the beginning of the 20th century.

Those in the remoter parts of the Kalahari who are unaffected by mining or other industry live in villages of between 200 and 5,000 people. Housing is mostly of the traditional type: single-roomed huts with mud walls and thatched roofs. Water is the limiting factor, confining settlement to places situated near wells or boreholes with potable water.

Cattle, the basis of the economy, are kept on the outskirts of villages, or at distances of up to 50 miles away. Except in the Ghanzi District of Botswana—where most of the livestock raising is done on private ranches, many of them owned by Africans—grazing lands are state-owned, and their use is regulated by local government councils. Wells and boreholes are owned by the councils, syndicates of cattle owners, or private individuals; year-round cattle grazing is limited to their vicinity. In summers of above-average rains, however, pastoralists may trek with their stock to remote pastures, where for a short time water may occur in pools. Cattle and goats feed upon a small range of the available vegetation. Since effective pasture management is little practiced, the grazing of these animals is highly destructive. Pasture loss and subsequent desertification are serious threats to the ecology of the Kalahari. Cattle are prized beyond their economic value, as their ownership is a measure of social status and personal worth. Thus, the desire to possess more cattle puts an increasing load on diminishing pasture, leaving it no chance for recovery. The traditional dangers to livestock—drought, disease, internal parasites, and wild predators—have diminished markedly as more boreholes have been sunk, veterinary care improved, and indigenous fauna have grown scarcer. In addition, wealthier cattle owners have improved their herds by introducing better stock and practicing scientific breeding.

Goats furnish most of the meat and milk for home consumption, and nearly all households cultivate crops of corn (maize), sorghum, and pumpkins. Because of the threat of drought, more crops fail than are successful. Wild food plants and the meat of game animals are important components of diet in the smaller and more remote villages. All villages have trading stores or are visited by hawkers who sell foodstuffs and other commodities.

All but the smallest villages have state-run primary schools, which are attended by the great majority of children, although few proceed to secondary education. State-run health clinics and hospitals in the larger villages supplement the services of herbalists and diviners.

Riding horses and donkeys are the usual means of local travel. Trucks belonging to traders or to the mine labour recruiting agency are used for longer journeys.

Large diamond deposits were discovered in Botswana soon after the country's independence, and the opening of the diamond mine at Orapa in 1971 marked the beginning of the development of mining activities in scattered locations of the Kalahari. In addition, tourism and the sale of handicrafts have become economically important.

The San—or Basarwa, as they are called in much of the region—are now either clients of Bantu-speaking pastoralists and work at cattle posts in return for support or they are employees of the cattle ranches of the Ghanzi District or are dependents of such employees. Few San still follow their traditional pattern of hunting and gathering (hunting and gathering culture). Many have been resettled by the government of Botswana from their traditional homes in the Central Kalahari Game Reserve to new villages built outside the reserve.

Although all San traditionally were hunter-gatherers, there were significant cultural and social differences between groups. For example, a number of groups had long-standing clientships with Bantu-speaking stockowners, while other groups lived—until the 1970s—solely as autonomous foragers. Of these latter peoples, the Kung (!Kung), !xong, and G/wi tribes (the “! ” and “/” representing click sounds) were intensively studied. While each group was distinct, the G/wi of the Central Kalahari Game Reserve can be considered an example of the traditional San hunter-gatherer way of life.

The G/wi lived together in bands, each consisting of 5 to 16 households linked by bonds of kinship and friendship. Each band had a recognized territory of 300 to 400 square miles, selected for its resources of food plants (the main part of the diet), wet-season water holes (used during the six to eight weeks when sufficient rainwater gathered in pools), trees (for shade, shelter, firewood, and wood for making artifacts), and areas of grazing to attract and sustain herds of game animals. Subsistence was based on a number of species of edible plants, of which eight were staples in their various seasons. This diet was supplemented by the meat of antelopes and other herbivorous mammals, by tortoises and other reptiles, and by the flesh and eggs of all but raptorial and scavenging birds. Plant-gathering was mostly done by women ranging within five miles of the camp, while men hunted over a much larger area. The main hunting weapon was a light bow shooting flimsy, unfletched, poisoned arrows. The range of these bows was only about 75 feet, and great skill was needed to stalk the quarry within this distance. Antelope leather provided material for clothing, which included cloaks that also served as blankets and carrying bags.

From November to some time between late June and early August—a period when there is sufficient food—the band lived as one community, moving from camp to camp every three or four weeks as the local supply of food plants became exhausted. Blighting frosts depleted the available food plants in winter (May to September), and the band would then split into its constituent households, each retreating to a separate part of the territory. Early-fruiting plants increased the food supply just before the approach of the wet season, allowing the band to reunite at a joint campsite. During dry seasons, shelters were little more than open windbreaks made of branches and grass. In rainy periods, domed structures of branches were thatched and made rainproof.

Europeans first entered the Kalahari early in the 19th century as travelers, missionaries, ivory hunters, and traders. The only European settlement was in the Ghanzi District, where a number of families were allowed ranching blocks in the 1890s. Until the 1960s they led a life of isolation and poverty, but since then they have been able to gain ownership of the land and improve their living conditions. Most other whites in the Kalahari are government employees or are engaged in private enterprise.

Because of its sparsely populated expanse, the Kalahari is served by infrequent roads and tracks, the majority of which are passable only by trucks or four-wheel drive vehicles. Maintained roads connect administrative centres, major habitations, and marginal farming areas in the south, southwest, and northwest. Constructed roads now link eastern Botswana with the Okavango Swamp and with mining developments south of the Makgadikgadi Pans.

The Kalahari's lack of surface water and deep sands constituted a major obstacle to early travelers. The Scottish missionary and explorer David Livingstone (Livingstone, David), with assistance from local peoples, traversed the Kalahari in 1849 with great effort by utilizing local waterholes. In 1878–79 a party of Boers (Boer) in the Dorsland (“Thirstland”) Trek crossed the Kalahari from the Transvaal to central Angola by a circuitous route, losing along the way about 250 people and 9,000 cattle, largely from thirst. The introduction of motor vehicles in the 20th century greatly improved transport into the Kalahari, but even as late as the 1950s large areas were virtually inaccessible and were never visited by outsiders. By the mid-1970s, however, vehicle mobility had improved to such a degree that the whole of the Kalahari had been opened to study, hunting, and tourist expeditions.