Afghanistan's shape has been compared to a leaf, of which the Vakhan strip forms the stem. The outstanding geographic feature of Afghanistan is its mountain range, the Hindu Kush. This formidable range is a barrier between the comparatively fertile northern provinces and the rest of the country, it creates the major pitch of Afghanistan from northeast to southwest. The Hindu Kush, when it reaches a point some 100 miles north of Kabul, spreads out and continues westward under the names of Baba, Bamyan, Safid Kuh (Paropamisus), and others, each section in turn sending spurs in different directions. One of these spurs is the Torkestan Mountains, which extend northwestward. Other important ranges include the Kasa Murgh, south of the Hari River; the Hesar Mountains, which extend northward; and two formidable ranges, the Mazar and the Khurd, extending in a southwestern direction. On the eastern frontier with Pakistan, several mountain ranges effectively isolate the interior of the country from the rain-laden winds that blow from the Indian Ocean, accounting for the dryness of the climate.
The Hindu Kush and subsidiary ranges divide Afghanistan into three distinct geographic regions, which roughly can be designated as the Central Highlands, the Northern Plains, and the Southwestern Plateau. The Central Highlands, actually a part of the Himalayan chain, include the main Hindu Kush range. Its area of about 160,000 square miles is a region of deep, narrow valleys and lofty mountains, some peaks of which rise above 21,000 feet. High mountain passes, generally situated between 12,000 and 15,000 feet above sea level, are of great strategic importance and include the Shebar Pass, located northwest of Kabul where the Baba Mountains meet the Hindu Kush, and the Khyber Pass, which leads to the Indian subcontinent, on the Pakistan border southeast of Kabul. The Badakhshan area in the northeastern part of the Central Highlands is the location of the epicentres for many of the 50 or so earthquakes that occur in the country each year.
The Northern Plains region, north of the Central Highlands, extends eastward from the Iranian border to the foothills of the Pamirs, near the border with Tajikistan. It comprises 40,000 square miles of plains and fertile foothills sloping gently toward the Amu River (the ancient Oxus River). This area is a part of the much larger Central Asian steppe, from which it is separated by the Amu River. The average elevation is about 2,000 feet. The Northern Plains region is intensively cultivated and densely populated. In addition to fertile soils, the region possesses rich mineral resources, particularly deposits of natural gas and oil.
The Southwestern Plateau, south of the Central Highlands, is a region of high plateaus, sandy deserts, and semi-deserts. The average altitude is about 3,000 feet. The Southwestern Plateau covers about 50,000 square miles, one-fourth of which forms the sandy Rigestan Desert. The smaller Morgowb Desert of salt flats and desolate steppe lies west of the Rigestan Desert. Several large rivers cross the Southwestern Plateau; among them are the Helmand River and its major tributary, the Arghandab.
Most of Afghanistan lies between 2,000 and 10,000 feet in elevation. Along the Amu River in the north and the delta of the Helmand River in the southwest, the altitude is about 2,000 feet. The Sistan depression of the Southwestern Plateau, 1,500 to 1,700 feet in elevation, was the seat of a flourishing ancient civilization that was ended in the 14th century by Timur (Tamerlane).