Tuesday, February 01, 2022

Geologists Have Redefined the Present Age, Calling the Last 4,200 Years the "Meghalayan Age"


Avery Thompson
Mon, January 31, 2022

What era are we in? Geologists have redefined the present age that human civilization is living in, deciding to call the last 4,200 years the "Meghalayan Age." This new classification will help scientists better understand the events of the last few thousand years.

Geologists break down our planet's history into eras, periods, epochs, and ages. Our current era is the Cenozoic, which is itself broken down into three periods. We live in the most recent period, the Quaternary, which is then broken down into two epochs: the current Holocene, and the previous Pleistocene, which ended 11,700 years ago.

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The Holocene began at the end of the last Ice Age, when glaciers started retreating. In that time, humans learned how to farm, built cities, and started launching rockets into space. From a human perspective, the end of the Holocene looks very different from the beginning. But from a geological perspective, has much really changed?

The 2018 announcement, from the International Commission on Stratigraphy, is an admission that there have been, in fact, significant transformations in Earth's geography. While the broader trend of warmer temperatures and receding glaciers holds just as true today as 11,700 years ago, there are other changes in the geologic record.

Around 4,200 years ago, a devastating drought lasted for at least 100 years and caused the collapse of civilizations around the world. It ended Egypt's pyramid-building Old Kingdom, the Akkadian Empire in modern-day Iran and Iraq, the Indus Valley Civilization in modern-day India, and the Liangzhu civilization in modern-day China.

Not only did this drought alter human civilization, it even left an imprint in the rock record. The drought can be seen in stalagmites in India, where the lower monsoon levels are represented by changes in oxygen isotopes. The global nature of the drought, the permanent record visible in rock layers, and the lasting effects to life on Earth mean that this moment in history is enough to qualify as the beginning of a new age.

The Meghalayan isn't the only new age that the International Commission on Stratigraphy identified. They also named the Greenlandian as the first age of the Holocene, ranging from 11,700 years ago to 8,200 years ago. This age ended when the planet abruptly cooled from melting glacial water flowing into the North Atlantic. There's also the new Northgrippan age, which sits between the Greenlandian and the Meghalayan.

These new divisions of geologic time will likely bring some order and clarity to an era defined by monumental change, but not all scientists agree that the new ages are the best way to reclassify recent history. In particular, some geologists are working on defining a brand-new era to succeed the Holocene, called the Anthropocene, or "human era."

"They've suddenly announced [the Meghalayan] and stuck it on the diagram," geography professor Mark Maslin told the BBC. "It's official, we're in a new age; who knew? We have lots of new definitions that perhaps now contradict the Anthropocene Working Group and go against what most scientists perceive to be the most important change on Earth in the last 10,000 years."

But it may be possible for both the Anthropocene and the Meghalayan to exist at the same time. And regardless, the Anthropocene is tough to define precisely—plenty of very smart people are struggling with the definition.

It's hard to say how this geologic debate will play out. Defining the past is clearly hard enough; what happens in the future is anyone's guess.

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