After reading the last column (‘Why Save the Rocks of the Deccan Plateau’, The Hindu , Nov 9, 2015), one reader asked: “What is the purpose behind saving them? Are there any reasons other than aesthetic?” This is a valid question that needs to be answered. After all, these rocks are not like tigers or lions which we want to save and not get extinct; they maintain an overall balance in the animal and vegetation population by feeding on other animals and herbivores, thus maintaining a dynamic equilibrium. But rocks and boulders are inanimate and sit there as stones. Why not use them for building, what role do they have in the scheme of things? If for aesthetics, let us preserve some and use the rest- so goes the argument.
The answer comes from history, namely the very birth, growth and evolution of our Mother Earth — its continents, climate and what we can learn from that. These rocks and boulders are remnants and reminders of the early history of our planet itself. Studying them enriches our knowledge of how our earth come to be, how she has adjusted over time to internal and external forces, and supports not just us humans, but millions of other life forms. It also tells us how and when millions of other life forms come to be, how they were lost and how the surviving ones have kept the relay, continuity and evolution of new forms of life.
It is now generally accepted, based on theoretical and observational basis, that the earth itself was born about 4.54 billion years ago. It came through the accretion or accumulation of the gaseous nebula of our Sun. Over time, it out-gassed itself through volcanic eruptions and began cooling and making a compact mass of itself, roughly a coconut- shaped globe (about 6300 km radius). Even today, its core is a hellishly hot (6,000 degrees C) fluid, while its body is a set of layers of crust, each cooler and cooler. Today the surface of the earth, the biosphere where we humans live (less than 100 km strip), has the highest temperature of 70 degrees C (the Lut Desert of Iran) and the lowest -89 degrees C (Vostok Station in the Antarctic). The granite boulders and the Deccan Basalt thus remind us of the grandeur of Mother Earth and the place we humans occupy, among the 1.4 million other life forms that she supports currently, and an even larger number that she did millennia (and billennia) ago.
Indeed, there is evidence now that within its very first billion years of its birth, earth supported life forms. This became evident as scientists could identify the carbon form (using which all life in earth thrives) called graphite. As the earth began cooling, three layers began forming- the core of about 3400 km radius, the mantle about 2,900 km radius above it, and the crust which is but 6-35 km thick on the surface where we live. The upper part of the mantle plus the crust are together called the lithosphere, which has several ‘plates’ called tectonics (from the Latin tectonic meaning building block). The lithosphere’s surface is covered by 7-8 major plates and several minor ones. These plates “float” on the soft “plastic” mantle below the crust. Earthquakes, volcanoes and the building of mountains occur across these plate boundaries when these plates collide.
In the beginning, the earth was just one globular mass. As the mantle and crust formed and the plates began colliding, continents were formed. Such re-adjustments of the land masses is a slow process and is thought to occur even now. (We recently heard how the plate under Reunion Island is hitting against the Asian plate, thus making the Himalayas grow in height inch by inch over time). And the signature rock of the continent, indeed the planet earth itself, is granite. And it is unique to Mother Earth. The other rocky planets Venus, Mercury and Mars are covered not with granite but with basalt. (I don’t know if we should boast about this when astronauts on future Mangalyans meet Martians (if any). But we of the Deccan can certainly pride ourselves that we see them, walk on them and appreciate their shapes and sizes everyday).
Unlike the older, blacker granite is the other rock, basalt (from the ancient Greek basanos or touchstone or the Egyptian bauhun, or slate), which has several hues to it. Mostly formed by the cooling of volcanic lava nearer the surface, basalt is far more common, and is found all across the earth both land and on ocean bottoms. Basalt thus reveals the history of volcanic eruptions and lava flows.
These then are not just history written in stone. They are, as Prof. Renne of California, Prof. Kanchan Pande of Maharashtra and Drs. K. Gopalan and K.V. Subba Rao of Deccan remind us, signposts of the ongoing saga of Mother Earth re-adjusting herself. They thus offer a perspective of not just human life but that of the earth itself. As the historian Prof. Romila Thapar points out: “To comprehend the present and move towards the future requires an understanding of the past- an understanding that is sensitive, analytical and open to enquiry”. Hence, let us preserve as much of the Rocks of Deccan as we can, for the future generations. They may study these and came with even more exciting findings.
dbala@lvpei.org
