CHAPTER 2 Natural Variables CHAPTER 2 NATURAL VARIABLES (Landform, Soil, Climate and Natural Resources) 2. Introduction: The spread of Harappan cultural elements into the regions of Punjab, Rajasthan, Haryana, Uttar Pradesh and Gujarat, towards the end of the 3rd millennium B.C. is well known. In these multidirectional penetrations the Harappans have demonstrated their skill in selecting suitable environmental niches suggesting that their settlement pattern was mainly influenced by the varied geophysical features of the land. While nature determines the route of development, man determines the rate and the stage (Taylor 1953). In other words nature creates imbalances in the form of relief, climate, biotic cover and mineral endowments and man operates in this setting. Harappan sites have been located all over the varied geophysical and environmental conditions of Gujarat state. 2.1 Gujarat in general. The state of Gujarat extends over an area of 187,115 Sqkms and consists of a variety of landscape formations (Fig: 2.a). On the one hand there are the fertile alluvial plains of the rivers such as the Tapi, Narmada, Mahi, Sabarmati, Saraswati and Banas and on the other there is the vast expanse of Salt waste of the Rann of Kutch. And while the Arabian coastline forms its western margin, the hills of the southern Aravallis, the western rim of the Vindhyas and Satpudas and the northern part of the Sahayadris form its eastern margin. Physiographically the region is divided into 3 distinct units or sub regions viz: Kutch, the Saurashtra 35 N N PHYSIOGRAPHY OF GUJARAT N Fig: 2.a 36 peninsula or Kathiawad and Mainland Gujarat. Mainland Gujarat can be further subdivided as North Gujarat and South Gujarat, mainly on the basis of environmental conditions. The region between Mt. Abu and Mahi river forms the arid zone of North Gujarat and the region between the Mahi and Damanganga rivers forms the fertile alluvial tract of South Gujarat. These divisions also form the cultural zones of Historical Gujarat (Majumdar 1965:17, Sankalia 1941:4-6). 2. l.a Ths. Landform The landform is made up of mainly two geological formations of which the most important is the Deccan trap formation of the Mesozoic (Fig: 2.b). It occupies the central and southern parts of Saurashtra, the southern mainland coast and also the central parts of Kutch. This formation is not uniform in thickness, varying from 213 mt. at Khambalia, 311 mt. at Jamnagar, 464 mt. at Dhandhuka and attains a maximum of 1117 mt. at Mount Girnar. In contrast to these ancient highland formations is the vast alluvial plains, which form the second important formation of Gujarat. Recent in origin it is the creation of fluviatile and marine deposition (Deshpande 1948:208-211). This low lying tract connecting the Saurashtra Peninsula with the mainland Gujarat is indicative of an esturine area during the Pleistocene time. According to Dikshit (1970:16) the depression is an outcome of tectonics during the Tertiary which in recent times was filled with alluvium. Although its basal complex is formed by harder crystalline deposits, it is the alluvium which determines the topography and land utilization. It also marks the most fertile 37 GUJARAT GEOLOGY CHARNIOCKITES 40 0 40 ao N N Fig: 2.b 38 zone of the state. The development of the Rann of Rutoh is also a recent geological phenomena. During the Pleistocene it was most probably a shallow arm of the sea into which the Indus and Saraswati of the Vedic times flowed. The growth of the desert conditions is due to the fact that this region lies along the well known northern desert belt. Besides the Aravallis are aligned parallel * to the progress of the*"winds, which allows for very little rainfall. The increasing^aridity and the large diurnal variations of temperature are instrumental in disintegrating the rocks and helping in the accumulation of sand, which is distributed by the action of winds (Wadia 1944:291). These Ranns have almost entirely isolated Kutch from the mainland, which in spite of its drying up in summer season is an effective barrier to human contacts. An important point to be noted here is that while this tract of saline marshy plain, scarcely above the sea level remains dry for one part of the year, it is covered by water for the other part. The 1884 Gazateer states that, 'during the south west monsoon the Cambay Rann joins the Nal and forms a connected sheet of water which spreads over the neighboring tracts of the Bhal and the Nal Kantha, turning the villages into islands and cutting off communication with Ahmedabad' (1884:78). According to Flam (1981:52-53), during 'the prehistoric period the central and western portions of the Lower Indus basin was probably a bay, with the coastline located somewhere north of Tatta and south of 39 Hyderabad. Terrestrial Rutch consisted of an island or islands and can be considered part of the Lower Indus basin'. In fact a very little depression of this tract would be enough to convert Sauarshtra and Kutch into Islands. Recent research observes that, even today the excess water of the Rann empties into the Gulf of Cambay via this tract (Dikshit 1970:15; Pandya 1983:62). It is mainly because of these recent natural formations that the state of Gujarat is categorically divided into the above mentioned three subregions. Next in important are the Jurassic limestone formations of Kutch, where they are bordered on the south by the Deccan traps and by the saline marsh of the Rann of Kutch on the North. The large part of Jurassic rocks to the east of Saurashtra around Dhrangadhra belongs to the same formation and is called the Umia horizon. 2. l.b. Siiils. Although the main feature of the physical setting of Gujarat is its orientation to the Arabian sea, it is the internal distribution of hills and plains which has affected the spread and growth of settlements. The soil especially, which forms the fundamental and locally important factor, is mainly a product of the bedrock geology of the region (Fig: 2.c). The most predominant soil in Peninsular India and Gujarat is the black cotton soil' also known as 'Regur'. Its origin is generally ascribed to long continued surface action on rocks like the Deccan Trap. 'The decomposition of the Basalt in sliil, would result in an argillenanceous or clayey residue, which by a long 40 T" N SOIL MAP OF GUJARAT DESERT SAMDY (SALINE ALLUVIUM - SANDY alluvium-SANDY LOAM COASTAL ALLUVIUM V-V MEDIUM BLACK SOIL DEEP BLACK SOIL 40 SO ie o ie 32 4a mis Fig: 2.C 41 cycle of secondary changes and impregnation by iron and decomposed organic matter resulting from ages of jungle growth over it, would assume the character of Regur' (Wadia 1944:305). The characteristic features of the black soil are 1. The depth varies from 1 to 2 feet and sometimes up to more than 20 feet. 2. It has a loamy to clayey texture 3. Heavy cracks in summer season which, especially in heavy rock clays, is more than 3 to 4 feet deep 4. Presence of lime kankar zone at some depths and free carbonates (mostly calcium carbonate) mixed in the soil. The soils are generally rich in montmorillontic and beideltic group of minerals (I C A R 1957). The moisture retentive qualities of the black cotton soil and its aeration by deep hot- weather cracking are well known; it swells when wet and shrinks when dry. This alteration ensures through mixing of soil particles. Unless tilled very soon after the onset of the rains, it is extremely sticky and difficult to work (Spate 1954:83). However Wallace says (1887) that the black cotton ploughs itself and can be loosened with the help of wooden ards; he notes "Black soil has wonderful power for absorbing water Although it continues to retain throughout an abnormal amount of moisture which is of great value to the crops grown on it and in short enables cultivation to be practiced without irrigation, at the same time in the dry weather, it loses a large amount of moisture and shrinks in consequence. The shrinking is in all directions, consequently very deep and wide cracks are formed... By the use of the Dutch hoe harrow the cracks are filled and 42 closed with the fine soil of the surface and by this means a regular circulation of soil is established. The cracks further fulfill the function of ploughing, by admitting air freely into the body of the soil (PP180-181)'. This soil is credited with an extraordinary degree of fertility and is excellent for dry cropping. Most of the black cotton regions are important cotton growing tracts. In several parts of Gujarat the black soils have been eroded and their character changed by stream transportation. The lowlands of North Gujarat are underlain by alluvium with local drifts of sand, derived from the wind and water erosion of the Aravalli range. Black soil is met with only in patches. Major portion of mainland Gujarat is covered with recent sub-aerial formation consisting mainly of the great loess or blown loam deposits. They are underlaid by the old alluvium of the great rivers, which is equally extensive but exposed only in the deep cut river valleys. This alluvium has obviously favored agrarian development in this part of the state, except along the sandy coast and the highland fringes in the northeast. 2.1.0. Climate Mainland Gujarat receives a rainfall of 800 to 1500mm, which is the maximum in the state (Fig: 2.d). Of course, the mountains or ghats along the eastern border receives more than adequate precipitation, but of little productive significance.