Speaker: Dr. Peter Molnar, professor of Geological Sciences, University of Colorado at Boulder, and fellow, Cooperative Institute for Research in Environmental Sciences 

Lecture Summary: Three million years ago, ice covered Canada for the first time, the first “Ice Age,” in hundreds of millions of years. In that first Ice Age, the sheet of ice covering Canada reached as far south as Missouri. Approximately 100 subsequent “Ice Ages” have occurred since that time, with the retreat from the last one occurring between 20,000 to 10,000 years ago. 

Concurrently, ancestors to mountain lions crossed the Isthmus of Panamá, from North America to South America to wreak havoc among animal life there, while giant Armadillo-like animals moved in the opposite direction into North America. Mountain lions and armadillos are but two among many species that made such journeys, in what biologists call the “Great American Interchange.” 

Many geologists who study past climates, “paleoclimatologists,” imagine that the Isthmus of Panamá emerged 3 million years ago, not only to provide a land bridge for the Interchange of animals, but also to isolate the Atlantic and Pacific Oceans, and as a consequence to alter ocean circulation. That circulation today includes features like the Gulf Stream, an ocean current that transports warm water from the eastern coast of the USA to western Europe. These paleoclimatologists infer that the marked change in ocean circulation created conditions that allowed ice sheets to grow on Canada and to give us recurring Ice Ages. 

Suppose, however, that you were a mountain lion, or an armadillo, would anything draw you into the swamps and jungles of hot, humid Panamá? Would you not prefer to remain in your semi-arid savanna than deal with snakes and crocodiles? 

During Ice Ages, Panama cools a bit and dries out, making it like the more arid climates where mountain lions, armadillo, and their brethren flourish. So, alternatively, could global climate change associated with that first big Ice Age have temporarily transformed Panamá’s mosquito-infested, uninviting jungles into a savanna highway conducive to overland travel? In terms of cause-and-effect, rather than the “Great American Interchange” signaling a change in the configuration of land and sea whose resulting ocean circulation facilitated the first Ice Age, could the “Interchange”, instead, be a consequence of the global climate changes due to that first Ice Age, whose cause would lie elsewhere, independent of the emergence of the Isthmus of Panamá? To understand Earth’s climate, we seek to explore different theories about our planet’s climate history that span human and geological time scales. 

Biography: Peter Molnar obtained a bachelor’s degree in Physics in 1965 from Oberlin College and Ph.D. in geology in 1970 from Columbia University, with a thesis in earthquake seismology. His initial work addressed aspects of plate tectonics. Following a 2-year post-doc at Scripps Institution of Oceanography and 4 months as an exchange scientist in the USSR studying earthquake prediction, he took an assistant professorship at MIT, where he turned his attention to the processes by which continents deform on a large scale and in particular how mountain ranges form. After 12 years of being dissatisfied with his teaching, he quit and returned to the life of a post-doc. In 2000, eager to change the direction of his research to include the study of how large-scale geodynamic processes have affected climate on geologic time scales, he took a position in the Department of Geological Sciences and became a fellow in the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado. 

Peter Molnar’s research focuses largely on these two questions: (1) how large-scale geodynamics cause deformation of the Earth’s crust, including earthquakes and the building of mountain ranges, and (2) how shifting continents, emergence of islands, growth of mountains, etc. affect climate on geologic time scales. His work has included fieldwork in remote parts of the world, and numerical calculations of processes that obey rules of fluid mechanics, but he is incompetent, and unwelcome, in a laboratory. He teaches a graduate seminar in “Tectonics and Climate,” and with Lon Abbott, he teaches an undergraduate writing course on geologic development of the Rocky Mountains. 

Peter Molnar received the 2014 Crafoord Prize in Geosciences for “for his ground-breaking contribution to the understanding of global tectonics, in particular the deformation of continents and the structure and evolution of mountain ranges, as well as the impact of tectonic processes on ocean-atmosphere circulation and climate.” 

The New England Aquarium is pleased to welcome the Lorenz Center’s 4th Annual John Carlson Lecture to the Simons IMAX Theatre. Understanding and predicting global climate change may be one of the most complex scientific challenges we face today. MIT’s School of Science launched the Lorenz Center, a new climate think tank devoted to fundamental inquiry. By emphasizing curiosity-driven research, the Center fosters creative approaches to learning how climate works. The annual Carlson Lecture features exciting new results in climate science each year to the general public, which is made possible by a generous gift from MIT alumnus John H. Carlson to the Lorenz Center at MIT. Register here.