The Scenic “Ghats” in the Deccan Plateau in Maharashtra
In December I got a phone call from a friend, Mark Richards, inviting me to join a small team of researchers on a trip to India. He said we would be looking for clues to the mystery of the extinction of the dinosaurs 66 million years ago.
It was an offer I could not refuse, and, indeed it proved to be an expedition of great adventure and learning – learning about how geologists, paleontologists and other scientists collect data and use modern scientific techniques to piece together interesting aspects of the earth’s history.
A Little Background
What killed the dinosaurs? It is now widely accepted that it was a large extra-terrestrial object (a meteorite or comet) that hit the earth 66 million years ago. The object was as large as a big city and came crashing into the earth at a speed of 30 km per second – so fast that it went through the earth’s atmosphere in a fraction of an instant. It pulverized the rocks constituting the earth’s crust where it hit, and penetrated all the way into the magma, creating fierce supersonic shock waves with the energy equal to millions of times the Hiroshima nuclear bomb. The rocks then rebounded violently throwing ejecta all over the earth. The ejecta included fused rock that had vitrified into glassy spherules called tektites.
The person most responsible for piecing this story together from the geological evidence is Walter Alvarez, Professor of Geology at UC Berkeley. He has written a beautiful book, T-Rex and the Crater of Doom, which I urge you to read. It is a page turner, an evocatively written scientific thriller, as Alvarez uncovers unmistakable evidence of the meteorite hit and finds its traces in the rocks around the earth. He then goes on to actually find the (then unknown) meteorite crater in the Yucatan peninsula in a triumph of scientific inference and painstaking geological exploration.
My Book Club fellow-member and friend, Mark Richards, now a Provost at the University of Washington, has been a Professor of Geophysics, University of California, Berkeley since 1994. He had induced us to read the book and later he introduced me to Walter Alvarez. I ended up funding a Ph. D. student (a paleontologist called Robert DePalma) who had made a remarkable find in North Dakota. and now has published some paradigm shifting papers. If you are curious about his findings read this very informative article in the New Yorker.
Does the Meteorite Explain Everything?
However questions still remain about how exactly the dinosaurs met their demise. The precise mechanism by which billions of dinosaurs and other species vanished forever is still not known – it takes a lot for abundant, well-adapted, dominant species inhabiting all of the niches of the earth for over a hundred million years, to go extinct. Paleontologists and evolutionary biologists are still making models to try and explain numerically how this could have happened from the aftermath of the meteorite hit.
One possible scenario has to do with a massive volcano eruption in India.
The Deccan Traps and our Area of Travel in India
The second largest volcanic eruption in earth’s history occurred in India – it lasted for a million years, and the lava flow created the entire Deccan plateau plus nine times the volume of the Deccan which is beneath the Arabian Sea. More than 500,000 cubic kilometers of lava was released – a small continent’s worth! By contrast the Mount St. Helens eruption was only about 1 cubic km. The basalts from this flow are called the Deccan Traps. The volcanic eruptions started before the meteorite impact, so were not initiated by it, but they went on for a long time after the impact. Some geologists believe that the meteorite hit was so severe – it caused a global earthquake of magnitude 11, according to a paper by Mark Richards – that it loosened the pathways of lava flow, making them substantially more voluminous and releasing life-destroying noxious gases, such as Sulfur-di-oxide that enveloped the earth for a long time. According to these geologists this was a contributing cause of the mass extinction.
Trip to the Deccan Plateau – January 2020
One such scientist, who was part of the team that I joined last month on the trip to the Deccan Ghats, is Paul Renne, Director of the Geochronology lab in Berkeley – a world class facility with state-of-the-art dating of rocks.
Above is a video of Paul Renne at an outcrop near Polladpur, Maharashtra. Paul has demonstrated that the rocks here are 66 (plus or minus 1) million years old and we are looking at lava deposits from before and after the meteorite hit, 66 million years ago. The “Polladpur” Formation on top (Post K-T boundary) represents a flood of lava, he believes was loosened by the meteorite impact. This released toxic gases in copious quantities causing mass extinction.
Paul uses Argon-Argon dating to very precisely determine the age of the Deccan basalts. He brought along his Ph. D student, Ande. Mark, Paul, Ande and I were also joined by Professor Kanchan Pande, a senior professor and geologist at IIT Bombay, who acted as our host and directed us to interesting sites and outcroppings straddling the dinosaur extinction geological boundary (known as the K-T boundary).
Paul, Ande and Kanchan drove more than 3500 km in the Deccan ghats and collected upwards of a thousand kg of rock samples for shipment to Paul’s lab and Ar-Ar dating.
At IIT Bombay: Ande, Paul Renne, Kanchan Pande and Mark Richards with bags of rock samples for shipment to the US.
Mark and I joined them for more than 1500 km driven over 6 days. I got to witness the process by which interesting rock candidates are identified and also to help in chiseling out samples!
It was a fun trip. The ghats are very beautiful – they make a rugged landscape of weathered plateau and deep sinuous river valleys. It was a pleasure to traverse this landscape and to sample some of the small towns, with their great food and welcoming local hotels.
Here are some pictures including our visit to the Sula winery in Nashik, 200 km north of Mumbai.
