 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 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
NOTE: The inform