Matt Jackson on the Heterogeneity of the Mantle

01/08/22 • 35 min

Matt Jackson is a Professor of Earth Science at the University of California, Santa Barbara. He probes the chemical composition of the mantle by analyzing trace elements and isotopes in hot-spot lavas from around the world. In the podcast, he describes the intriguing heterogeneity among the hot-spots of the so-called “hot-spot highway” in the western Pacific. The heterogeneity there, as well as on larger spatial scales is challenging our ideas about the motions of the mantle over the billions of years of Earth history.

Previous Episode

Carmie Garzione on Reconstructing Land Elevation Over Geological Time

Throughout geological history, various points on the Earth’s surface have been lifted up to great elevations and worn down into low, flat-lying regions. Determining surface elevation histories is difficult because rocks that were once on the surface are usually eroded away or buried. Furthermore, most rock-forming processes are not directly affected by elevation. But it turns out that we can overcome these challenges, as Carmie Garzione explains in the podcast.

Carmie Garzione is Dean of the College of Science at the University of Arizona. She has managed to pin down the history of elevation changes by analyzing stable isotopes of carbon and oxygen in carbonate rocks. She describes how the method works, and presents her findings for the Tibetan plateau and the Andes. They show pulses of very rapid (geologically speaking) uplift. What might this be telling us about what has been going on in the lower crust and upper mantle in these regions?

Next Episode

Bob Hazen on the Evolution of Minerals

New rock types emerge during the history of the Earth. For example, the silica-rich felsic rocks such as granite that characterize continental crust, accumulated during the course of Earth history. Granite only forms in certain specific tectonic settings, such as above subduction zones and when lower crustal rocks melt in mountain belts. But what about the minerals themselves? Have they been around since the Earth formed, or did they too only appear on the scene later as a result of some geological process?

The question of how and when the minerals evolved is a relatively new subject, and was, and continues to be, pioneered by this episode's guest. Bob Hazen is Senior Staff Scientist at the Earth and Planets Laboratory of the Carnegie Institution for Science and Professor of Earth Sciences at George Mason University. At a Christmas party in 2006, a well-known biophysicist asked him the question: “Were there clay minerals in the Archean?” Apparently, nobody had given this much thought prior to 2006. The topic quickly became the focus of his research, rapidly blossoming into a whole new branch of mineralogy.