New clues into mass dinosaur extinction

From the Daily Princetonian: New clues into mass dinosaur extinction

To test an alternative theory explaining the 65-million-year-old mass extinction that led to the demise of the dinosaurs, Princeton University researchers developed a model that more accurately accounts for the Earth’s heterogeneities and offers different interpretations from previous models.

The researchers, who were based in the lab of geoscience and applied and computational mathematics professor Jeroen Tromp GS ’92, focused on a theory that explained the mass extinction as the result of a long volcanic eruption triggered by a meteorite strike near Chicxulub on Mexico’s Yucatan Peninsula. This theory suggested that the strike could trigger volcanic activity on the opposite side of the globe.

The project started in May 2010 and was the result of a collaboration between the first author, Matthias Meschede of the University of Munich, and co-authors Conor Myhrvold ’11 and Tromp. Myhrvold was previously a staff photographer for the ‘Prince.’

Meschede, who got involved through the University’s Visiting Student Research Collaborators program, said that the project was interesting for him because it focused on an unconventional source of earthquakes.

The original calculation for a link between the meteorite strike and the catastrophic volcanic eruptions included an analytical approximation based on a spherical earth model that failed to account for the heterogeneities of the Earth. The Princeton research showed the model to be very inaccurate.

“The Princeton group could simulate earthquakes on a global scale better than anybody else could before, and so we could take into account all the heterogeneities of the earth and make a much more accurate calculation,” Meschede said.

The Princeton model showed that, while a symmetric Earth focused seismic waves more strongly on a single point, a non-spherical Earth with heterogeneities spread waves over large areas that decreased the amplitude of earthquakes on the other side of the planet.

As a result, the amplitude of the Earth’s maximum ground displacement in the previous model was decreased by a factor of five; moreover, the Princeton model showed that heterogeneities basically filtered out the highest wave frequencies so that these frequencies became scattered and didn’t interfere constructively.

“This is basically the main difference, and so we think it’s a very important effect that you have to account for,” Meschede said.

Meschede also noted that, based on their findings, a relation between the meteorite strike and volcanic eruptions large enough to cause a mass extinction is unlikely.

In addition to providing more information on the possible connection between the eruption and the meteorite strike, the research has also created a model that could offer insight on the surface of other planets based on past collisions.

“For every meteorite impact, when you want to figure out what’s going to happen on the Earth, the moon, Mercury or Mars you have to consider the focusing effect on the other side, and if you want to see how large this is going to be, then you have to model it like we did,” Meschede said.

Because the Princeton model showed that the focusing factor was decreased by a factor of five when heterogeneities and the Earth’s asymmetry were taken into account, Meschede noted that vast improvements are possible with this more accurate model.

“Apart from that, just being able to simulate the heterogeneities, not just for the meteorite but also for other impacts and other planets — this is the development from the last five to 10 years,” Meschede said.