Many processes in geology affect the temperature of rocks.  Erosion is one example — as a surface is eroded, the rocks below get closer to the surface, cooling as they go.  So if we know the temperature history of a rock, we can infer its erosion history.  Becky Flowers has a thermochronology lab in which she determines the cooling history of rocks as recorded in specific crystals they contain, such as zircon and apatite.  She explains how this works, and how she has used her results to unravel histories such as that of the Grand Canyon, the South African plateau, and even of that of the lunar surface.
Becky Flowers is a Professor of Geological Sciences at the University of Colorado, Boulder. She has a thermochronology lab in which she measures the amounts of the different radioactive decay products within crystals to figure out the cooling history of rocks. Knowing how rocks cooled gives us new insights on geological histories and processes of many parts of the Earth, and even of the Moon.
For podcast illustrations, and to learn more about Geology Bites, go to geologybites.com.

Becky Flowers on Deciphering the Thermal History of Rocks

What moves the continents, creates mountains, swallows up the sea floor, makes volcanoes erupt, triggers earthquakes, and imprints ancient climates into the rocks? Oliver Strimpel, a former astrophysicist and museum director asks leading researchers to divulge what they have discovered and how they did it. 

To learn more about the series, and see images that support the podcasts, go to geologybites.com.
Instagram: @GeologyBites
Twitter: @geology_bites
Email: geologybitespodcast@gmail.com

Science

Earth Sciences

At roughly 15-25-million-year intervals since the Archean, huge volumes of lava have spewed onto the Earth’s surface. These form the large igneous provinces, which are called flood basalts when they occur on continents. As Richard Ernst explains in the podcast, the eruption of a large igneous province can initiate the rifting of continents, disrupt the environment enough to cause a mass extinction, and promote mineralization that produces valuable mineral resources. 

Richard Ernst studies the huge volcanic events called Large Igneous Provinces (LIPs) — their structure, distribution, and origin as well as their connection with mineral, metal, and hydrocarbon resources; supercontinent breakup; and mass extinctions. He has also been studying LIP planetary analogues, especially on Venus and Mars. He has written the definitive textbook on the subject.
Ernst is Scientist in Residence in the Department of Earth Sciences, Carleton University, Ottawa, Canada, and Professor in the Faculty of Geology and Geography at Tomsk State University, Tomsk, Russia. 

Richard Ernst on Large Igneous Provinces

Perhaps as many as five times over the course of Earth history, most of the continents gathered together to form a supercontinent. The supercontinents lasted on the order of a hundred million years before breaking apart and dispersing the continents. For decades, we theorized that this cycle of amalgamation and breakup was caused by near-surface tectonic processes such as subduction that swallowed the oceans between the continents and upper mantle convection that triggered the rifting that split the supercontinents apart. As Damian Nance explains in the podcast, newly acquired evidence suggests a very different picture in which the supercontinent cycle is the surface manifestation of a process that involves the entire mantle all the way to the core-mantle boundary.


Damian Nance draws on a wide range of geological evidence to formulate theories about the large-scale dynamics of the lithosphere and mantle spanning a period going back to the Archean. A major focus of his research is the supercontinent cycle.  He is Distinguished Professor Emeritus of Geological Sciences at Ohio University.

Damian Nance on What Drives the Supercontinent Cycle

The Earth’s tectonic plates float on top of the ductile portion of the Earth’s mantle called the asthenosphere. The properties of the asthenosphere, in particular its viscosity, are thought to play a key role in determining how plates move, subduct, and how melt is produced and accumulates. We would like to know what the viscosity of the the asthenosphere is, and how it depends on temperature, pressure, and the proportion of melt and water it contains. Few mantle rocks ever reach the Earth’s surface, and those that do are altered by weathering. So, as he explains in the podcast, David Kohlstedt and his team have tried to replicate the rock compositions and physical conditions of the mantle in the lab.  Using specially-built apparatus, he has been able to determine the viscosity of the asthenosphere to within an order of magnitude, which is an enormous improvement on what was known before.

David Kohlstedt is Professor Emeritus at the School of Earth and Environmental Science at the University of Minnesota.

David Kohlstedt on Simulating the Mantle in the Lab

In many countries, nuclear power is a significant part of the energy mix being planned as part of the drive to achieve net-zero greenhouse-gas emissions. This means that we will be producing a lot more radioactive waste, some of it with half-lives that approach geological timescales, which are orders of magnitude greater than timescales associated with human civilizations. In the podcast, Claire Corkhill discusses the geology such storage sites require, some new materials that can confine radioactive isotopes over extremely long timescales, and the kind of hazards, including human, we need to guard against.

Claire Corkhill is Professor of Mineralogy and Radioactive Waste Management in the School of Earth Sciences at the University of Bristol, UK. 

Claire Corkhill on Geological Radioactive Waste Disposal

We have learned a great deal about the geology of the Moon from remote sensing instruments aboard lunar orbiters, from robot landers, from the Apollo landings, and from samples returned to the Earth by Apollo and robot landings. But in 2025, when NASA plans to land humans on the Moon for the first time since 1972, a new phase of lunar exploration is expected to begin. What will this mean for our understanding of the origin, evolution, and present structure of the Moon? A lot, according to Mahesh Anand. For example, as he explains in the podcast, satellite imagery suggests that volcanism continued for much longer than was previously thought, perhaps until as recently as 100 million years ago.  In-situ inspection and sample return should help us explain this surprising finding. 
Mahesh Anand is Professor of Planetary Science and Exploration at the Open University, UK.




Becky Flowers on Deciphering the Thermal History of Rocks

Download our free app to listen on your phone