SHAlINI SAKSENA speaks to geologists about the significance of the new geological age, the Meghalayan Age, named after the rock caves in the north-eastern hill State
We owe a lot to the ancient Indians, teaching us how to count. Without which most modern scientific discoveries would have been impossible
— Albert Einstein
India is a land of sages. But many have forgotten the country’s glorious past and the contributions that scholars and scientists made centuries ago in Maths, Science, Astrology and Astronomy, to name a few.
We all know zero has an entirely Indian descent. We also gave the world the decimal system the Fibonacci numbers and their sequence by Pingala. If this was not enough, we gave the world binary numbers — the basic language in which computer programmes are written today. Ancient Indian mathematicians often applied their knowledge to make accurate astronomical predictions.
Hence, when geologists recently revealed that the recent age in Earth’s 4.54 billion year history began 4,200 years ago and has officially been designated the Meghalayan Age, after the Indian State, it came as no surprise.
There is a story behind how this era was discovered in India. It all began with a global drought that had a devastating effect on civilisations from Egypt to China. The concept of the Meghalayan Age came up seven years back because of particular chemical signatures found in the stalactites and stalagmites in the hill caves of Meghalaya.
“The findings of the Meghalayan Age find their origin in the caves Krem Mawmluh in Sohra. The Meghalayan christening happened only after analysing stalagmites. Ages are determined on the basis of significant events of that part of history. The Meghalayan Era has been determined by the drought 4,200 years back giving no scope for the settled population in that era to migrate. This period is also marked with active migration of people. Human fossils found in the region give an insight into the humans of that time. Through them, the impact of the Meghalayan Age on the humans has been studied,” Professor Dr D Walia, Department of Environment Studies, North East Hill University, Shillong, explains.
He tells you that the caves were under study due to the presence of limestone. The waterfalls here lead to cracks that become conduits on the surface and seep into the caves to fall on the same point and since it has calcium, stalagmites keep growing. “After analysing these, one found that 4,200 years back, there was a drought for 200 years since there was no deposition during this time,” Dr Walia says.
He adds that the findings in the Indian State are important as this era was only dominant in the rest of the world like in Greenland rather than this part of Asia. Therefore, from the geological point of view, finding of remnants of the Meghalayan Age is significant.
“There are different ages determined by chronostratigraphy (branch of stratigraphy that studies the age of rock strata in relation to time). This means that there was an event that left a mark — climate change that led to it — excessive rains that converted to drought. These are very clearly recorded on the history of the Earth in the rocks. This will help researchers, students and invite geo-tourism to the State. It will remain in the history books forever,” Dr Walia says.
The finding of this Age is of importance for climatologists, especially those who opine that the climate change is due to industralisation and urbanisation. Not that humans do not play a critical role, they do but it is Nature that plays a major role and has the underlying control.
Another uniqueness of this age is that this is the first interval in Earth’s geological history that has coincided with a major cultural event, as agricultural societies struggled to recover from the shift in climate.
Interestingly, the need for such a classification arose to avoid any confusion. According to Prof Stanley C Finney, Secretary General, International Union of Geological Sciences, Department of Geological Sciences with California State University at long Beach, US, the Holocene Epoch is the youngest unit of this rank on the Geologic Time Scale.
“It represents the time from 11,700 years ago to the present. The huge community of Earth scientists working on this period of Earth history have long subdivided the interval into the informal units early Holocene, middle Holocene and late Holocene. The community of Holocene Earth scientists requested that the International Commission of Stratigraphy (ICS) of the IUGS formally define these units to prevent confusion. For example, events that some placed in the early Holocene were placed in the middle Holocene by others. The Holocene scientist prepared a formal proposal that defined three new subdivisions and submitted it to ICS for approval,” Professor Finney says.
Also, there is a reason why it is called the Meghalayan Era. The geologic time scale is hierarchal with units of different rank ranging from Eon to Era to Period to Epoch to Age. The Holocene is an Epoch; subdivisions of Epochs are Ages.
The ICS requires that each age has a formal name derived from geographic area that provides the best geologic record used to define the boundary between it and previous Age. The new IUGS-ratified subdivisions of the Holocene Epoch are the Greenlandian, Northgrippian, and Meghalayan Ages, in order from oldest to youngest. The name Meghalayan is derived from the region of Meghalaya in Eastern India because a stalagmite that grew over time in a cave in that region contains the geologic layer that marks the boundary between the Northgrippian and Meghalayan.
Prof Mike Walker, Emeritus Professor of Quaternary Science, University of Wales says that the subdivision of the Holocene that has been proposed, with three clearly-defined stages is concerned with the past record of climate change. “We are using climate markers — the 8,200 year cold event and the 4,200 drought event to subdivide the Holocene. We have an Early Holocene (11,700-8,200), a Middle Holocene (8,200-4,200) and a late Holocene (4,200 to present). We have named these as the Greenlandian, Northgrippian and Meghalayan stages respectively. The early Holocene was a period of generally rising temperatures; maximum temperatures were achieved and maintained during the Middle Holocene; while the late Holocene was characterised by increased climatic instability with, for example, increases in monsoon and El Niño–Southern Oscillation activity. In Northern high latitudes we also saw readvances of glaciers,” Professor Walker says.
He also opines that the division is of considerable value to geologists. “It enables them to define specific periods of time, to see whether those time intervals are different from each other (and whyij) and it also helps us to link (correlate) sequences in one locality with those in another. This is very important in building a history of the Earth,” he tells you.
Once the era has been classified, there is need for an update the timeline for Earth’s history as well. Our knowledge of past history of the Earth comes from the rocks that compose the Earth formed over time. We interpret events in Earth history from rocks. We establish the time scale based on the order in which the rocks formed. We give specific names to bodies of rock representing specific time intervals. For example, the Jurassic System.
“The name is then used to refer to the time interval during which the rocks formed — Jurassic Period. The geologic time scale has developed over 200 years as geologists studied rocks worldwide and reconstructed Earth’s history.
“As more and more information becomes known, the time scale has evolved to better reflect the new knowledge. The term Holocene, and the rocks on which it is based, have been known for 150 years. With more intense study such that happens today, we are better able to subdivide the rocks (geologic record) into units of higher resolution. Therefore, the term Holocene was sufficient for discussing Earth history for more than 100 years. But the more modern studies and advanced knowledge of today requires subdivision of the Holocene Epoch into units of higher resolution — the Ages. Refinement of the Geologic Time Scale — new units, better defined boundaries — is an ongoing process,” Professor Finney says. He tells you that the things that geologists have found in Meghalayan era is the cultural impact of the global climate change 4,200 years back, which marks the beginning of the Meghalayan Age; how human societies worldwide re-established themselves, flourished and grew into the modern world that we have today.
Believe it or not, geologists use the units of the geologic time scale for efficient communication. The term Jurassic Period has a very specific meaning; it refers to not just an interval of time but also to all the events that occurred in that time interval. It is easier to speak of events in the history of England (UK) by the reigns of monarchs (Henry 8th, Victorian Era) rather than the years (1843-1906).
We are living in the Meghalayan Age, which is the youngest subdivision of the Holocene Epoch, which is the youngest subdivision of the Quaternary Period, which is the youngest unit of the Cenozoic Era, which is the youngest unit of the Phanerozoic Eon.
like everything new, this new era is under scanner as well as some researchers have objected to its creation. There is still an active debate about assigning a new geologic slice of time. “The only objections are those who want to rename this part of earth history as the Anthropocene Epoch,” Professor Finney says.