The rocks that joined the Americas: Is there a connection between climate and evolution of life?

Written by Dania Puente, CAS communications intern

photo of Esteban GazelAs part of the GeoPRISMS Distinguished Lectureship Program, Miami University's Department of Geology & Environmental Earth Science was proud to host Dr. Esteban Gazel on Thursday, March 1 in Shideler Hall.

Gazel is currently an associate professor in the Department of Earth and Atmospheric Sciences at Cornell University. In his public lecture he discussed the "young continent," or isthmus, that connects the Americas.

Having grown up in Costa Rica, Gazel developed his interests there in volcanoes and earthquakes, which fostered his curiosity to understand the secrets of our planet. Today, his research explores the role of melting processes in the evolution of planet Earth. He studies life cycles of mantle plumes, the evolution of intra-oceanic arcs and continental crust production, as well as the integration of petrology-geochemistry with seismic and geodynamic studies, and volatilities in the mantle.

He first described GeoPRISMS as a "community-driven" organization and recognized the great work they do, followed by the introduction of his main topic: continent formation. Gazel captivated the audience with the relationship between Central America and the Galapagos Islands, where he's conducted most of his research.

"Between the Galapagos Islands and Central America, there is a series of volcanic islands that are now submerged," Gazel explained at the beginning of his talk. "Thanks to the movement of tectonic plates and the process of subduction, we have Central America today."

"In the case of the Galapagos there is a thermal anomaly that comes all the way from the core-mantle boundary, creating a big convection anomaly," he added.

map showing separated Americas, 10 million years ago

Ten million years ago
North and South America
were not connected.

In order to understand our planet and why there is life, he went on, it is important to recognize its "unique characteristics" compared to other planets. Planet Earth has a continental crust, which supports all life.

"The crust is the life-sustaining interface between the interior of the planet and the exosphere," Gazel explained. "Life happens in this interface, and without it, there wouldn't be life on this planet."

Nevertheless, the crust needs to have a certain composition.

"Water and plate tectonics are a key to continent formation," he said, and then moved on to explain the geochemistry behind oceanic and continental crust and how the isthmus (that is now Central America) formed.

"When the isthmus closed and connected North and South America, it changed the way all ocean currents and trade winds moved," he stated.

This is important because it enabled a significant exchange of fauna between the continents that were once separated. South America was full of marsupials just like Australia, and as soon as the isthmus closed all these animals began to move, causing the extinction of many. Gazel emphasised that "the oceans control climate," and by changing global circulation there was a change in climate, one that caused the African Savanna to go from a jungle to what it is today.

Gazel concluded his talk by showing footage from his unpublished Nova documentary. He received many questions asked by the audience, covering a wide range of topics, and showed results from several other related studies to explain his answers more in depth.

"This talk was very exciting as it highlighted the close interactions between fundamental geologic processes, such as plate tectonics and magmatism, and the evolution of climate and life on Earth," said Liz Widom, chair of the Department of Geology and Environmental Earth Science and host for the GeoPRISMS lecture. "Most people don't recognize that deep mantle plumes from the core-mantle boundary played such a significant role in shaping the world as we know it today."

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