B. Climate 



This entire area lies under the influence of the two monsoonal seasons that 

 typify Southern and Eastern Asia. During the summer months, southwest monsoon 

 surface winds blow from the southwest parallel to the arid Arabian coast south of 

 Ra's Al Hadd and, consequently, contribute little or no moisture to this area . On 

 reaching the Gulf of Oman, there is some divergence with a southeast branch 

 blowing into the Gulf. Southwest winds reaching the northern Pakistan coast are 

 generally deflected eastward owing to the almost continuous presence of a series 

 of lows . These lows move east to west over the Indo-Gangetic plain and cause a 

 counter-clockwise circulation of air . Hot, dry continental air moving to these 

 lows across India rises above and stabilizes the warm moist air from the Arabian 

 Sea . This effect accounts for the extreme aridity of this northeastern region despite 

 the Inflow of abundant moisture. From Bombay southward, abundant precipitation 

 occurs along the coastal margin due to the orographic effect of the Western Ghats. 



The winter monsoon season is a time of variable northerly winds in the Gulf of 

 Oman with a high frequency of calms. The most frequent wind direction is from the 

 northwest although at times the northeast wind blows with exceptional force. These 

 northeast winds are often heavily laden with dust. Along the Pakistan coast and 

 southward, the northeast wind dominates during this season. 



Spring and fall are the two transitional seasons during which northerly winds 

 give way to southerly and vice versa . In general, the southerly winds prevail for 

 the longer period of time . 



As a consequence of topography and prevailing winds, there is little precip- 

 itation in the coastal regions of the study area, and during any season of the year, 

 desert conditions predominate. Dust storms are common, occurring with greatest 

 frequency during the summer months, especially along the Makran coast of Pakistan 

 and Iran . Dust in the Makran area has been reported to a height of 15,000 feet, 

 but it usually does not exceed 10,000 feet. Prevailing surface winds during this 

 season of maximum occurrence would tend to prevent this material from being dis- 

 tributed seaward, but in the vicinity of Gwadar, winds above 6,500 feet are al- 

 most entirely northerly during this season, providing a transporting agent out over 

 the sea . 



C . Regional Geology 



General reviews of the geology of the study area are presented by Wodla (1953) 

 and Pilgrim (1908). The southern portion along the Indian coast is dominated by the 

 Tertiary Deccan volcanics. These lavas ore generally uniform augite basalts al- 

 though locally more acidic and basic valcanics occur. Also exposed in the area 

 roughly between the Arovalli and Vindhya Mountains are several complex systems 



