Tell us about yourself

Just like most of us, Attreyee Ghosh is intrigued by what goes on deep down inside the earth. Unlike the rest of us however, Ghosh is striving to unravel some of the mysteries deep down.

“A lot of complex physical processes continuously go on inside the earth and our accumulated knowledge about these is very limited,” says Ghosh, a computational geoscientist, who is setting up a state-of-the-art geodynamics laboratory at IISc.

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Using highly powerful computers for number crunching, Ghosh’s team – consisting of geologists, physicists and mathematicians – plans to put together a three-dimensional model of the insides of the earth.

What did you study? How did you end up in such an offbeat, unconventional and cool career?

“My love for science started early on. Staring at the night sky I was struck with a burning curiosity about what lay in those distant worlds of planets and stars. Watching Carl Sagan’s Cosmos on television, with my dad explaining many of the things that I didn’t understand as an eight-year-old, filled me with wonder.”

It is this “wonder” and the excitement of exploring the unexplored, that inspired Attreyee to be a scientist. “There are so many things we are yet to learn about our universe, about our own planet! We are still discovering new things about the Earth; it’s fascinating!,” she remarks.

As we have all studied in school, the earth has a central core consisting mainly of hot iron, an intervening zone of molten rocks called the mantle and the upper crust, on which we live. The upper crust is divided into different tectonic plates which move around. The movement of these overlying plates is controlled by, among other things, an upward flow of extremely hot fluid from the core to the “relatively” cool mantle and a corresponding downward flow of cold crust into the mantle. “The processes that go on inside the earth hold the key to many geological mysteries,” says Ghosh, who studied geology at the undergraduate level at Calcutta University. She subsequently did her master’s degree from the Indian Institute of Technology Bombay and Lamont-Doherty Earth Observatory  at Columbia University.

While at Columbia, Ghosh happened to choose a course in plate tectonics. “The course dealt with fundamental questions about earth’s processes, the driving forces behind plate tectonics, and the associated controversies. It was an eye opener about all the things we are yet to learn about this planet,” says Ghosh.

“The theory of plate tectonics may not be as grand as the theory of evolution but it is quite holistic and can answer many questions,” Ghosh told KnowHow.

After receiving a Master’s degree from Columbia, she joined the PhD program in Geosciences at Stony Brook University, NY. There, she worked on the problem of how the mantle couples with the lithosphere, and how this coupling gives rise to surface deformation. On completion of her PhD, Attreyee joined the Geodynamics lab at the University of Southern California (USC) as a postdoc. After the frozen winters of New York, the sun and the warmth of southern California were a welcome change.

What do you do?

Attreyee joined IISc in 2012, the same year in which she published a paper in Science showing how the convective flow in the mantle, along with lithospheric topography and density, can explain global plate motions and stresses. She and her students at the Computational Geodynamics lab in IISc strive to understand how surface phenomena, like movement of tectonic plates, formation of mountains, breaking apart of continents, and earthquakes, are affected or sometimes caused by what’s happening deep inside the Earth’s mantle.

Among the things that currently hold the interest of Ghosh and her young colleagues is a mysterious gravity anomaly, just south of the Indian peninsula. A ship sailing across this gravity anomaly, known as the Indian Ocean Geoid Low, would drop by 100 metres into the ‘hole’ and would rise up again by 100 metres “all without doing any work against gravity,” says Ghosh.

The source of this anomaly probably lies more than 700 kilometres deep in the earth’s lower mantle, although the exact reason for this anomaly in still unknown. “Studying such anomalies is one of the few ways we can learn about what is happening deep inside the planet,” says Ghosh, who did her PhD and postdoctoral studies at Stony Brook University in New York, before she joined IISc in 2012. “Such gravity anomalies are a big mystery,” she says.

“The big question that we are trying to address in our lab is: how much of the processes that we see on the surface of the earth, such as earthquakes, the movement of plates, the formation of mountains, rifting of continents, and volcanic eruption can be explained by what is happening deep inside the earth as opposed to things that happen in the shallow part, say, within 100 kilometres from the surface,” she says.

Geophysicists all over the world currently use indirect methods to understand the earth’s internal processes. For instance, dedicated networks of GPS (global positioning system) stations are used to monitor movements of tectonic plates.

To peer inside the earth, the scientists use a technique called seismic tomography, which is guided by the same principle as a CT-scan. While radiologists use X-rays to image different parts of the brain and a 3-dimensional model is put together by combining the images, geophysicists use seismic waves to get a 3-dimensional picture of the earth’s interior. When an earthquake occurs, it generates seismic waves, much like ripples in water created by dropping a pebble. These waves travel through the earth collecting information about the layers through which they pass. Seismic stations all over the world log this information round the clock and store it.

Ghosh says what she does is curiosity-driven science. But that doesn’t mean it has no practical application. The new knowledge that emerges from her studies may help unlock many mysteries. One, for instance, is the phenomenon of intraplate earthquakes such as those which struck Latur in 1993 and Bhuj in 2001.

Your advice to students?

She thinks that students from early on should be inculcated with a “scientific temperament”. This is not only useful to become a scientist, but also to become a good citizen, a responsible member of the civil society. “Critical thinking in children must be encouraged and as scientists, we should do more to ensure that the excitement of science reaches everyone. I want everyone to experience the thrill that I feel when I read about the discovery of gravitational waves or understand the far reaching implications of that discovery,” she says.