Exploring the Physical World

When the Earth Shakes

WEIZMANN NOW, Fall 2003 • TAGS: Earth, Physics

How many people can say that their job is directly related to those long, glorious days of childhood, when the only responsibility you had was to be home in time for dinner? Dr. Einat Aharonov is one of the lucky ones. Throughout her youth, she enjoyed long hikes, and contemplating the forces that shaped the mountains, rocks, and land that she loved.

"As a child, I was fascinated by how mountains were once under the sea and that you could find seashells on mountain sides," she says. "I wanted to understand the large forces of nature that could do that."

Now, as a researcher at the Weizmann Institute of Science, she studies these forces, devising ways to compress events that take eons in geological time so that they can be studied in her lab. Her interests are in the forces that move the Earth, from the slowly shifting tectonic plates that make up the Earth's crust to the physics of granular motion that describe the motion of massive landslides. The only problem? The phenomena are difficult to capture in the controlled settings of a research lab. Studying these events within a human lifetime—using manageable pressures and temperatures—requires computer models, analog materials such as salt or silicone, and most of all, innovation.

In one of her current projects, Dr. Aharonov and one of her doctoral students are looking at how massive landslides occur using computer models and boxes filled with fine sand. "The computer can simulate collections of grains, which can flow like fluid yet behave like solids at the same time," she says. Her research has shown that large-scale landslides are a result of the way particles move, conserving their kinetic energy through a bouncing motion. When this happens in nature—a phenomenon Dr. Aharonov dubs "spontaneous subchronization"—it can amplify a relatively small triggering event and cause devastatingly large landslides to flow unexpectedly across large distances. Dr. Aharonov and her student are in the process of writing a scientific report on this research, which she has shown in two-dimensional models. Her student is working on establishing a model to test the work in three dimensions. But there are still more dimensions to her research. Dr. Aharonov is also looking into the forces that work on tectonic plates. Rather than watching the plates themselves, which drift only inches a year, Prof. Yossi Mart of Haifa University and Dr. Aharonov have partnered with a laboratory in Sweden. Together they are using centrifuges to artificially enhance gravity and speed up geological time—at least in the lab—to see how the giant interlocking pieces of the Earth's crust move in relation to each other.

"We're trying to understand the physical processes that take place at the point where oceans meet continents," she says. Dr. Aharonov does not just study how the Earth is moved, but how it is formed. Her team is also looking at how rocks are formed and how they dissolve over time, again using special techniques and materials to speed up the process in the lab.

Since joining the Weizmann Institute in 2000, Dr. Aharonov has had an opportunity to be a force of her own, aiding in the development of a relatively new department at the Institute: the Environmental Sciences and Energy Research Department, a growing group of dedicated researchers who investigate everything from atmospheric chemistry and ocean and climate dynamics to solar energy. "It is very exciting to be a part of building this new department and these new studies," she says.

Dr. Aharonov hopes that enhanced understanding of the geophysical processes she is studying may facilitate engineering measures to better prepare us for the next time the Earth suddenly fails beneath us—as it inevitably will.

Dr. Einat Aharonov is the incumbent of the Anna and Maurice Boukstein Career Development Chair.