Geology Bites

Torgeir Andersen explains how continental rocks in western Norway were dragged roughly 100 kilometres into the mantle during the collision of Baltica and Laurentia, and then returned to the surface. Coesite inclusions provide evidence of ultrahigh-pressure metamorphism. The conversation examines subduction, slab break-off, exhumation and whether isolated diamond-bearing rocks record local overpressure rather than greater burial depth.

Hosted by Oliver Strimpel

Brian Wernicke explains lithospheric extension and the origins of the Basin and Range Province. The discussion explores how geologists reconstruct large-scale stretching of the crust and what these observations reveal about deformation and continental evolution.

Hosted by Oliver Strimpel

Bernhard Steinberger examines whether volcanic hotspots provide a fixed reference frame for plate motion. The discussion combines paleomagnetic records, island-chain ages and mantle-flow models, showing how plumes can drift with mantle circulation. Contrasting the Hawaiian and Louisville tracks helps distinguish hotspot motion from changes in plate direction and illustrates the limits of treating hotspots as stationary.

Hosted by Oliver Strimpel

Sonia Tikoo explores the unresolved history of the Moon’s magnetic field. Lunar samples indicate a strong early field followed by a much weaker field that persisted far longer than expected. The discussion weighs proposed dynamo mechanisms, paleomagnetic measurements and the difficulty of explaining both the field’s early strength and its long-lived weak tail.

Hosted by Oliver Strimpel

Steve Brusatte discusses the dinosaurs that survived the end-Cretaceous asteroid impact: birds. The episode follows fossil evidence for feathered dinosaurs and the emergence of avian traits, then considers how surviving bird lineages diversified after the extinction. Publisher illustrations connect fossils, anatomy and evolutionary relationships.

Hosted by Oliver Strimpel

Alec Brenner explains how palaeomagnetic measurements reveal independent motion of the East Pilbara and Kaapvaal cratons about 3.5 billion years ago. The evidence moves the detection of relative plate motion much earlier and constrains models of early Earth tectonics. It rules out a permanently stagnant surface without establishing that modern plate tectonics already operated, and also informs questions about the core and atmosphere.

Steve Jacobsen describes how laboratory experiments reproduce the extreme pressures and temperatures found inside planets. He explains how the behaviour of minerals under those conditions informs models of planetary interiors and discusses work at the NSF Center for Matter at Atomic Pressures.

Esther Sumner describes direct observations of turbidity currents and the challenge of instrumenting active submarine canyons. Smart boulders and acoustic current measurements reveal how these large, long-lasting underwater flows transport sediment. The discussion includes an underwater robot’s accidental encounter with an active current in California’s Mendocino Canyon.

Hal Levison explains how Jupiter’s Trojan asteroids could help distinguish competing accounts of Solar System evolution. The discussion compares scenarios in which giant planets formed near their present orbits with models involving substantial migration from a more compact configuration. It considers why the Lucy spacecraft’s observations can test these ideas and how discoveries of other planetary systems sharpen the questions.

Sara Pruss discusses archaeocyath sponges, the first multicellular reef builders, and their relationship to diversification during the Cambrian. The episode traces successive reef-building groups through the geological record and asks why reefs repeatedly emerge despite environmental disruption and extinction.

Michael Manga explains how water changes volcanic eruptions, including explosive interactions between magma and external water and the effects of dissolved water as magma depressurizes. The discussion includes the 2022 Hunga Tonga eruption and extends to water-related volcanism on Mars and icy moons.

Carina Hoorn examines how the Amazon Basin’s geological evolution shaped its extraordinary biodiversity. The discussion connects Andean uplift, fresh sediment supply and marine incursions during the Early Miocene with the diversification of aquatic environments and ecological opportunities.

Anat Shahar investigates how rocky planets acquire water, a question central to assessing habitability beyond Earth. Her experiments and models examine chemical reactions between hydrogen-rich atmospheres and early magma oceans. The episode considers why water formation matters alongside a planet’s distance from its star.

Keith Klepeis explains how magma travels from deep crustal sources into the upper crust and crystallizes into plutons. Observations from southern Fiordland in New Zealand reveal the resulting structures and constrain their origin and evolution. The discussion links magma transport with the three-dimensional organization of intrusive rocks.

Tom Herring introduces high-precision geodetic measurements using satellite navigation, very-long-baseline interferometry and radar interferometry. He explains how improved accuracy and cheaper receivers expand studies of plate motion, earthquake-related deformation and Earth rotation, with further applications in infrastructure and agriculture.

Jiří Žák reconstructs the Cadomian and Variscan mountain-building episodes preserved in central European geology. He connects continental movements and supercontinent assembly with surviving metamorphic and volcanic rocks, granites and deformation structures. Field studies and zircon geochronology help recover the history of heavily eroded mountain belts.

Claudio Faccenna explores why subduction zones retreat, advance, move sideways or reverse direction over geological time. The discussion examines interactions between descending slabs and their surroundings, including neighbouring subduction systems. Mediterranean examples illustrate how convergent margins evolve over tens of millions of years.

Cees Van Staal traces the Paleozoic tectonic events that built the Appalachians and their connections with the Caledonian mountains. He distinguishes that ancient assembly from the origins of today’s landscape, which also reflects Atlantic rifting, associated magmatism and much later glaciation.

Andreas Fichtner explains progress and obstacles in seismic imaging of Earth at regional and global scales. He discusses the evidence supporting three-dimensional maps of mantle plumes, continental interiors, mid-ocean ridges and large low-shear-velocity structures, and how improved methods increase confidence in the images.

Renée Tamblyn examines when and how thick, silica-rich continents emerged from Earth’s early magma-ocean state. The discussion compares gradual growth with episodic formation and explores the role of water released from hydrated minerals in oceanic lithosphere. It also considers hydrogen production by early geological processes and its possible relevance to life.