Pakistan is divided into three major geographic areas: the northern highlands the Indus River plain, with two major subdivisions corresponding roughly to the provinces of Punjab and Sindh and the Balochistan Plateau. Some geographers designate additional major regions. For example, the mountain ranges along the western border with Afghanistan are sometimes described separately from the Balochistan Plateau, and on the eastern border with India, south of the Sutlej River, the Thar Desert may be considered separately from the Indus Plain. Nevertheless, the country may conveniently be visualized in general terms as divided in three by an imaginary line drawn eastward from the Khyber Pass and another drawn southwest from Islamabad down the middle of the country. Roughly, then, the northern highlands are north of the imaginary east-west line the Balochistan Plateau is to the west of the imaginary southwest line and the Indus Plain lies to the east of that line (see fig. 5).

The northern highlands include parts of the Hindu Kush, the Karakoram Range, and the Himalayas. This area includes such famous peaks as K2 (Mount Godwin Austen, at 8,611 meters the second highest peak in the world), and Nanga Parbat (8,126 meters), the twelfth highest. More than one-half of the summits are over 4,500 meters, and more than fifty peaks reach above 6,500 meters. Travel through the area is difficult and dangerous, although the government is attempting to develop certain areas into tourist and trekking sites. Because of their rugged topography and the rigors of the climate, the northern highlands and the Himalayas to the east have been formidable barriers to movement into Pakistan throughout history.

South of the northern highlands and west of the Indus River plain are the Safed Koh Range along the Afghanistan border and the Sulaiman Range and Kirthar Range, which define the western extent of the province of Sindh and reach almost to the southern coast. The lower reaches are far more arid than those in the north, and they branch into ranges that run generally to the southwest across the province Balochistan. North-south valleys in Balochistan and Sindh have restricted the migration of peoples along the Makran Coast on the Arabian Sea east toward the plains.

Several large passes cut the ranges along the border with Afghanistan. Among them are the Khojak Pass, about eighty kilometers northwest of Quetta in Balochistan the Khyber Pass, forty kilometers west of Peshawar and leading to Kabul and the Baroghil Pass in the far north, providing access to the Wakhan Corridor.

Less than a one-fifth of Pakistan's land area has the potential for intensive agricultural use. Nearly all of the arable land is actively cultivated, but outputs are low by world standards (see Agriculture , ch. 3). Cultivation is sparse in the northern mountains, the southern deserts, and the western plateaus, but the Indus River basin in Punjab and northern Sindh has fertile soil that enables Pakistan to feed its population 1000 n under usual climatic conditions.

The name Indus comes from the Sanskrit word sindhu, meaning ocean, from which also come the words Sindh, Hindu, and India. The Indus, one of the great rivers of the world, rises in southwestern Tibet only about 160 kilometers west of the source of the Sutlej River, which joins the Indus in Punjab, and the Brahmaputra, which runs eastward before turning southwest and flowing through Bangladesh. The catchment area of the Indus is estimated at almost 1 million square kilometers, and all of Pakistan's major rivers--the Kabul, Jhelum, Chenab, Ravi, and Sutlej--flow into it. The Indus River basin is a large, fertile alluvial plain formed by silt from the Indus. This area has been inhabited by agricultural civilizations for at least 5,000 years (see Early Civilizations , ch. 1).

The upper Indus Basin includes Punjab the lower Indus Basin begins at the Panjnad River (the confluence of the eastern tributaries of the Indus) and extends south to the coast. In Punjab (meaning the "land of five waters") are the Indus, Jhelum, Chenab, Ravi, and Sutlej rivers. The Sutlej, however, is mostly on the Indian side of the border. In the southern part of the province of Punjab, the British attempted to harness the irrigation power of the water over 100 years ago when they established what came to be known as the Canal Colonies. The irrigation project, which facilitated the emergence of intensive cultivation despite arid conditions, resulted in important social and political transformations (see The British Raj , ch. 1).

Pakistan has two great river dams: the Tarbela Dam on the Indus, near the early Buddhist site at Taxila, and the Mangla Dam on the Jhelum, where Punjab borders Azad Kashmir. The Warsak Dam on the Kabul River near Peshawar is smaller. These dams, along with a series of headworks and barrages built by the British and expanded since independence, are of vital importance to the national economy and played an important role in calming the raging floodwaters of 1992, which devastated large areas in the northern highlands and the Punjab plains (see Irrigation , ch. 3).

Pakistan is subject to frequent seismic disturbances because the tectonic plate under the subcontinent hits the plate under Asia as it continues to move northward and to push the Himalayas ever higher. The region surrounding Quetta is highly prone to earthquakes. A severe quake in 1931 was followed by one of more destructive force in 1935. The small city of Quetta was almost completely destroyed, and the adjacent military cantonment was heavily damaged. At least 20,000 people were killed. Tremors continue in the vicinity of Quetta the most recent major quake occurred in January 1991. Far fewer people were killed in the 1991 quake than died in 1935, although entire villages in the North-West Frontier Province were destroyed. A major earthquake centered in the North-West Frontier Province's Kohistan District in 1965 also caused heavy damage.

Data as of April 1994