P. Krishnamurthy

Volcanology and lava flow morpho-types from the Koyna-Warna region, western Deccan Traps, India

Flow mapping and physical volcanology of 15 basaltic lavas exposed in three critical road pass sections (ghats) in the Koyna-Warna region of the western Deccan Traps is presented in this paper. Transitional lavas like rubbly pahoehoe are most common morpho-type exposed in these ghat sections. Sinking of rubbly breccia into flow interiors and formation of breccia-cored rosette are common in some lava flows. Few rubbly lavas exhibit slabby tendencies. The amount and nature of the associated rubble is variable and result from the mechanical fracturing and auto-brecciation of the upper vesicular crust in response to distinctive stages in the cooling, crystallization and emplacement history of individual lava flows. Occurrence of aa and pahoehoe morpho-types in the lava flow sequence is subordinate. Three prominent pahoehoe flows separated by red bole horizons are seen in the upper parts of the Kumbharli ghat. These are thick, P-type sheet pahoehoe. The pahoehoe lavas represent compound flow fields that grew by budding, endogenous lava transfer and inflation. Presence of pahoehoe lavas in the Koyna-Warna region hints at possible hitherto unrecorded southern extension of Bushe-like flow fields. This study reconfirms the existence of pahoehoe-slabby-rubbly-aa flow fields and transitions even in the upper echelons of the Deccan Trap stratigraphy. The study of morphology and internal structure of lava flows exposed at the ghat sections in the Koyna-Warna region could guide subsurface core-logging that is critical in deciphering the physical volcanology and emplacement dynamics of basaltic lava flows penetrated by drill holes sunk under the scientific deep drilling programme.

Foundation day 2016–A report

Research Group, Centre for Ecological Research, IISc, Bengaluru, the key speaker of the day spoke on “Carbon Footprint and Changes in Climate”. He highlighted the challenges posed by various anthropogenic, CO2 emission sources such as electricity, industry, agriculture, transportation and the municipal waste disposal sector which together become the sources of principal greenhouse gas emissions. Unplanned and rapid urbanisation with conversion of wetlands, green spaces, lake beds and minor drainage/streams into high-rise concrete structures often with glass facade that are not conducive to tropical climates have led to problems such as flooding, decline in groundwater table (from 28 m to 300 m in a span of 20 years) and enhanced per capita electricity consumption in the city which leads to larger carbon foot print. They have also led to 79% decline in water bodies and 78% reduction on vegetation cover in the Greater Bengaluru area. The city with a population of about 98.8 lakh has only about 14.8 lakh trees, far shorter than the average of about 8 trees per person. Surface and atmospheric temperatures during the last decade have increased by 2-2.5°C due to anthropogenic heat sources such as the concretising of large areas, higher electricity consumption, increased burning of fossil fuels by ever increasing number of automobiles for transportation and unscientific methods of The 58th Foundation day of the Geological Society of India, Bengaluru was celebrated with a workshop on ‘Climate Change, the Paris Accord and the Indian Commitment’ at Conference Hall, Khanija Bhavan, Department of Mines and Geology. R.H. Sawkar, Secretary delivered the welcome address. M.S. Rao introduced the theme and drew attention to the increase in CO2 levels in the atmosphere from 280 ppm, prior to the beginning of the industrial revolution in the late eighteenth century to the current CO2 levels that have crossed 400 ppm level resulting in appreciable global warming. He highlighted the general consensus of scientific opinion endorsed by leading science academies of the world that anthropogenic activities and greenhouse gas emissions are the primary cause for the present situation. However, there are strong and respected dissenting voices (albeit a minority). M.S. Rao also quoted a recent article from Nature about Climate Change (25 April 2016) on Greening of the Earth wherein it has been found that CO2 fertilization has prompted trees/plants to sprout extra foliage equivalent in area to twice the continental USA based on satellite imagery analysis. He opined that our understanding of climate change and its impact thus needs to be more precise. T.V. Ramachandra, Co-ordinator, Energy & Wetland NEWS AND NOTES 261