Photo caption: Basalt rocks of the Deccan Traps in Western Ghats at the Arthur Seat Point in Mahabaleshwar, Maharashtra
Global warming is a burning issue affecting the earth. Discussed in all forums at the international and regional levels, this issue is a worry worldwide because its impact is devastating. Various methods are being proposed to effectively combat this problem. Some of them are both unconventional and unique.
After being introduced to Earth Sciences and its plethora of sub-disciplines, I chanced upon one such unique and interesting method to combat the climate crisis. This method is based on resources that are naturally-occurring and abundantly present. Therefore, it can be implemented on a large scale and be very cost-effective. The method involves the use of rocks known as picritic basalts.
In India, these basalts were formed approximately 65 million years ago and are present in the Deccan Trap region. They have a special type of mineral called plagioclase phenocryst that absorbs, i.e., sequesters, carbon dioxide (CO2). Carbon-capturing by basalt has been on-going for eons. This process is very slow and takes millennia. However, this time period can be reduced to just a few years if we powder the basalt.
Through the National Team Field Investigation, a project of the International Earth Science Olympiad 2022, we collectively understood and appreciated the importance of basalt. Our idea of reducing global warming through sequestration by rocks was inspired by one of the Negative Emission Technologies proposed in the COP 21 in 2015, when the Paris Agreement was signed. This project also became a stepping stone for me, as it changed my perspective of a rock from a seemingly mundane and dull hard object to a vault of secrets.
Our project was a collective field investigation by four members, including me, under the mentorship of Dr Hema Achyutan, a Professor in the Geology Department of Anna University, Chennai. We four team members were from Kerala, Maharashtra, Rajasthan, and Tamil Nadu. Since these regions have diverse topographies, we were able to collect different rock samples and conduct their detailed analysis. We effectively collected laterite (an extremely old weathered rock formed due to intense leaching), picritic basalt (a rock formed from lava flows millions of years ago), fine grained basalt, and charnockite (an extremely old weathered rock formed due to metamorphism of molten magma). A sample of calcrete was also analyzed. An unusual type of rock called red bole, so called because of its colour, was also considered.
Field photographs: (1) Top-left: Columnar basalt from Jhalawar district, Rajasthan; (2) Top-right: Weathered charnockite from Muttukadu, Chennai; (3) Bottom-left: Laterite on the banks of Bharathapuzha River, Kerala; (4) Bottom-right: Outcrop in the Deccan Traps at Daundaj, Pune.
To find out the amount of different ingredient compounds present in these samples, we used the X-Ray Fluorescence method. Before these samples were analysed by our complex instruments, we cleaned, powdered, and melted the samples. This was crucial to ensuring that there were little to no impurities or even water molecules present in them, which could hinder our observations. The results given out by this analysis aimed to determine the rock that is the best for sequestering carbon.
We found that a sample from the lowermost flow of lava at the outcrop in Maharashtra was quite different from other samples. This contained a peculiar mineral—plagioclase—which looks like a star under a microscope and can absorb CO2. The basalt that contains this kind of mineral, therefore, is quite effective for carbon sequestration.
Photo caption: Powdering an agate rock; preparing rock bead samples for testing
The Karha River basin and similar other basins located in the eastern part of Western Ghats are identified as the most suitable for mining basalt. The basalt dust can be extracted efficiently in this region by digging especially designed wells. Spreading this dust can increase the absorption area of basalt, which will help in sequestering CO2 quickly.
The basalt dust is also known to enhance soil quality and increase crop production. It can be particularly beneficial to this region which is otherwise very arid, dry, and has saline groundwater. Due to the lack of soil fertility, farmers here often have an unstable livelihood. So, we proposed the usage of powdered basalt as it is a very cost-effective fertiliser. It can transform an entirely barren and fallow land into a lush green place within months.
Further research will discover the full potential of this technology. This will not only help the people who for generations have not untapped the enormous potential of the rocks over which they have lived. But it will also help us curb the greater menace of global warming.