The tiny state of Meghalaya has played a significant role in deciphering the history of our planet. The past 4,200 years of the Earth’s history is today classified as a new distinct age, the Meghalayan Age. One stalagmite—a rock formation rising from the floor of the cave, found in the Mawmluh cave in Meghalaya provided the clue that led to the discovery of this new age. The onset of the age was marked by a severe drought due to which a large number of civilisations across the world seem to have ceased to exist. The effects of the drought are speculated to have lasted for over two centuries and it severely impacted people in Egypt, Greece, Syria, the Indus Valley, and the Yangtze River Valley.
First published in June 2012, the concept of the Meghalayan age was proposed in a discussion paper by a working group of INTegration of Ice-core, MArine, and TErrestrial records (INTIMATE), a French focus group, and the Sub-Commission on Quaternary Stratigraphy, a constituent body of the International Commission on Stratigraphy (ICS), the largest scientific organisation within the International Union of Geological Sciences (IUGS). The paper outlined the geological age of the stalagmite found in the caves, dating it through a process in which an age is assigned to the target material and then the history of the earth is calculated in relation to time and major events in its past (Fig. 1). This includes break-up of continents and radical changes in the planet’s climate (Walker M., 2012). After six long years, the proposal to further break the Holocene into three ages was finally accepted. On July 13, 2018, the International Commission on Stratigraphy (ICS)—the official geological time-keeper, upgraded the geological charts with the introduction of the new age. The Meghalayan age is the new official age that we are living in.
Khadg Singh Valdiya, a renowned Indian geologist, while expressing his thoughts on the new geological phase to a G’nY correspondent, says, “There have been multiple expeditions over the past few decades to such caves, where scientists have tried to learn more about the current age and epoch we are living in. There have been many expeditions by Indian scientists as well, who have been testing the stalagmites’ different components. The results have brought forward a new geological age, the Meghalayan age, which is a great honour for the state and our country.”
Stalagmites and stalactites are formed by the deposition of calcium rich material brought by the water percolating into caves or any other sheltered environment. The layers represent each cycle of deposition that can be dated by isotopic methods. The cone shaped deposit that grows from the ground upward is called stalagmite while the deposit hanging from the roof is known as stalactite. The geologists that tested the stalagmites in the caves in Meghalaya discovered an anomaly at the 4.2 interval, which marked the beginning of the Meghalayan age.
Geologists have divided the last 4.6 billion years of Earth’s existence into various slices of time. The Meghalayan age is the third division of the Holocene epoch/series, along with Greenlandian and Northgrippian ages. The Holocene epoch began roughly 11,700 years before the current time, the period which is referred to as the Greenlandian age, which spanned for nearly 3,500 years. The Northgrippian age came next, spanning about 4,000 years, finally succeeded by the age we are currently living in—the Meghalayan. The Holocene epoch, along with the Pleistocene epoch shapes the Quaternary system/period, which is part of the Cenozoic era/eraithem, which in turn is a division of Phanerozoic eon/eonothem, one of two eons that make up our planet’s entire history (International Commission on Stratigraphy, 2018).
Meghalayan Age | The Anthropocene
The inclusion of the Meghalayan age is not the only new geological phase making rounds over the past few years. Many in fact believe that the influence of human activity on the planet should be marked by a new geological classification, which they tentatively call the Anthropocene epoch. Professor Jan Zalasiewicz from the University of Leicester, a consistent supporter of the Anthropocene epoch and Chairperson of the Working Group on Anthropocene, in a communication to G’nY points out: “The subdivision of the Holocene, now ratified, is independent of the work on the Anthropocene. However, it does provide useful context and comparison in our studies of the Anthropocene, which have been discussed in lengths. For instance, we have described the changes we associate with the Anthropocene, for which we consider the optimal starting point is the mid-1950s, such as very large perturbations of the carbon, the production of ‘minerals’ and ‘rocks’ such as metals, plastics and concrete now on a planetary scale, and increasingly profound changes to the biosphere. We have suggested that these are rather larger in scale, and have much longer-lasting planetary effects than the sharp, but brief and relatively moderate climate perturbations that mark the boundaries of the newly ratified subdivisions of the Holocene. For this reason, we suggest that the Anthropocene, considered this way, is a larger scale phenomenon than the Meghalayan, consistent with the suggestion that the Anthropocene represents an epoch-scale event that marks the end of Holocene conditions on Earth.”
The inclusion of Meghalayan age adds a new chapter to the history of the planet. The Meghalayan age is different from other intervals of the geological timescale as it commences with a large-scale climatic event spanning across the globe. Professor Jan Zalasiewicz summarises, “Meghalayan age is useful because it gives a precise definition of these time intervals and so helps with clear scientific communication. It should not, though, particularly influence how we see other ages.”
Walker M.C.J., M. Berkelhammer, S. Bjork, L.C. Cwynar, D.A. Fisher, … and H. Weiss, 2012. Formal subdivision of the Holocene Series/Epoch: a Discussion Paper by a Working Group of INTIMATE (Integration of ice-core, marine and terrestrial records) and the Subcommission on Quaternary Stratigraphy (International Commission on Stratigraphy), Journal of Quaternary Science, 27(7): 649-659.
International Commission on Stratigraphy, 2018. International Chronostratigraphic Chart, Available at: https://bit.ly/2vBn91L