The territory, where the basin of the Kābul river, a tributary of the Indus, is removed, belongs to inland Asian areas. The most typical features of these areas are presented by the Iranian plateau, which despite its relative proximity to the sea is among the driest areas in the world. The whole of southern Afghānistān can be considered a desert, where the course of the Hilmand or Helmand river (here generally dry in summer) separates the great salty and steppe plain of Dāsht-i Margo from the bleak Registān desert. The most depressed points are occupied by salt marshes and lakes, among which the largest are the Gōd-i Zirah (430 m.) At the extreme S., and further north, towards Persia, the two Hāmūn-i Farāh (or -i Salvari, about 500 m) and Hāmūn-i Savarān [or -i Puzak, 510 m.), into which the Helmand and the other courses of water that bathes the Afghānistān of S. and SW. The lake basins break the desolate uniformity of the steppe expanses and the sandy or encrusted deserts of dazzling salts. The desert continues, becoming gravelly and stony, even on the mountains that rise in the middle or on the edges of the plateau; mountains that appear steep, bare, arid, in contrast with the deep valleys that furrow them and in which there is coolness and an abundance of water and arboreal and herbaceous vegetation.
Of the chains enclosing the Iranian plateau, only a small part of the great southern arch belongs to Afghānistān, with the internal slope of Toba Kokar (Sulaimān) and Sefīd Kūh (culminating with Sikaram at 4761 m.); while the system of the northern marginal chains belongs entirely to him, to the east of the deep transversal notch of the middle Harī Rūd. This mountainous complex, straddling which Afghānistān extends widely, and which can therefore be called the Afghan system, presents a bundle of three main chains directed from W to E. The median axial chain, more than 1300 km long., In the western half takes the name of Paropamiso or Bānd-i Bābā and culminates at 3590 m.; then it continues, rising more and more towards E., with the Hindū Kush (Indian Caucasus), whose major peaks exceed 7000 m. A series of longitudinal valleys separates the axial chain from the northern chain, which with various names (Bānd-i Turkestān, Khōgiah Moḥammed etc.) rises on the edge of the plateau, dominating the sandy expanses that descend to the mū Daryā. Even better delineated is the longitudinal valley, largely crossed by the upper Harī Rūd, which from Herāt to the Kābul valley is depressed between the axial chain and the southern chain of the system: the latter is distinguished with the names of Sāfīd Kōh and Kasamurgh in the sector O., Bānd-i Baiān in the center, Kōh-i Bābā in the E. sector, and pushing its peaks from 3-4000 m. in the first section at 5000 and 5143 in the last. To these or to the Hindū Kush are connected some chains from the Registān desert towards the NE., Such as those of the Kūh- i Wālā (3865 m.), Kūh-i Sāngan (3930 m.) Kūh-i Khūrd (3986 m.), and the others that close the cool basin of the Kābul river rich in waters. For Afghanistan geography, please check franciscogardening.com.
The morphology and geology of all these reliefs are little known. In the area between Herāt and Kābul both the axial and the southern chain give the impression of a very ancient mountainous landscape, leveled by erosion, then rejuvenated following an energetic uplift, with a strong deepening of the hydrographic network in a system of steep valleys slopes. Real frightening gorges are the very deep transversal notches through which the Harī Rūd, the Murghāb and the tributaries of the Āmū Daryā bend down towards N. Terraced alluvial conglomerates of up to 100 m. of power fill the bottom of the valleys, indicating a Quaternary climate much richer in rainfall; the glacial traces are limited to the elevated cirques.
The geological series includes:
1) Crystalline schists with granite and porphyritic rocks, which are present in the major chains and transpire under recent deposits also in the plains towards Persia and Belūcistān.
2) Paleozoic schists, sandstones and marine limestone, at least partly devonic and carbonic, reported in the Hindū Kush, in the Kūh-i Bābā and in the districts of Herāt and Kābul: to SE. of Kāhul there are metamorphosed paleozoic sediments covered by Permo-Triassic marine limestone with Himalayan facies.
3) Jurassic freshwater and terrestrial soils with coal beds, and red sandstones of the lower Cretaceous, reported both in the axial chain and in the chain immediately to S., and also at the base of the northern chain.
4) Limestones of the upper Cretaceous period, forming almost the entire northern range and widespread in most of the region.
5) Marine soils of the lower Miocene, followed by very powerful Miocene deposits of brackish and lagoon water, both towards the Aralo-Caspian depression and in the internal Iranian basins; Pliocene and Quaternary lacustrine and terrestrial lands.
6) Various volcanic rocks that seem for the most part tertiary.
The region, previously corrugated and subject to long erosion, underwent an energetic uplift towards the middle of the Miocene, which isolated the large internal Neogenic basin, where the progressive evaporation had the effect of depositing huge saline and chalky banks.
These banks are widely exploitable. Among the other mineral resources of the region, still poorly known, are cited: sulfur (at least in part of volcanic origin) towards the borders with Persia (the greatest quantities come from Hazāra and Pīrkisrī towards Sīstān), coal (Jurassic) in the Northern ‘Afghānistān, lead and antimony in various districts (Feringhial in the Ghorband valley in the upper Koksha valley and near Herāt), iron (devonic hematite from Hindū Kush, magnetite from the Paghman chain), silver (ancient mines from the Panǵshīr valley), gold (small quantities in the Laghman rivers), rubies (ancient mine of Susst, in the upper Amū Daryā), lapis lazuli (classic mine of the upper Kolksha valley, like the previous one in the extreme NE of the region).
The minimum temperature observed in Kābul is −2o °; the maximums vary from 32 ° to 38 °. The coldest months are January and February, the hottest July and August. The daily and annual temperature variations are large. The annual variation is between 25 ° and 28 ° (Kerki 27 °, Pamirski Post 32 °, Kelāt 20 °, 5, Ciāman 24 °, 8, Peshāwar 23 °, 1). The diurnal variation oscillates from 15 ° to 20 °. Kābul is in a large basin valley, which in summer heats up strongly and in winter is swept by cold winds.
Atmospheric pressure is highest in February, lowest in October. In the winter there are high pressures; the air then flows towards the low pressure areas at S. and SW. As in the Īrān, the period of high pressure coincides with the rains, that of low pressure coincides with drought. N. winds blow from the centers of great pressure in Central Asia, almost always in the winter. In summer, from May to November, when the pressure is low, the sky is always blue, cloudless, and rain is very rare. Also in this period in the rān and in most of the Afghānistān there are winds of the N. In the northern Afghānistān the rains begin in mid-October. November is cloudy, with frequent rains; December is dull, wet, cold. January and February are the coldest months, March is variable;
The Paropamiso constitutes a natural division for the climate: in January and February snow often falls, especially on the mountains up to Giagdalak, but towards the E. the snow stops; Gelālābād has a very sweet climate, roses and daffodils bloom in the middle of winter, while in Kābul and Siyāh Kush there are very intense colds.
The Afghānistān is on the whole a transition region between the climate of the etesî winds and the climate of the monsoons, a transition region between India and the rān.