Geology Bites

The Himalaya are just one, albeit the longest and highest, of several mountain ranges between India and Central Asia. By world standards, these are massive ranges with some of the highest peaks on the planet.  The Karakoram boasts four of the world’s fourteen 8,000-meter peaks, and the Hindu Kush, the Pamir, the Kunlun Shan, and the Tien Shan each have many peaks above 7,000 meters.  No mountain r...

The Caledonian orogeny is one of the most recent extinct mountain-building events. It took place in several phases during the three-way collision of continental blocks called Laurentia, Baltica, and Avalonia during the early stages of the assembly of the supercontinent Pangea. In the process, Himalayan-scale mountains were formed. While these mountains have been worn down today, we still see plent...

With most of Greenland buried by kilometers of ice, obtaining direct information about its geology is challenging. But we can learn a lot from measurements of the island’s geophysical properties — seismic, gravity, magnetic from airborne and satellite surveys and from its topography, which we can see relatively well through the ice using radar. In the podcast, Joe MacGregor explains how he created...

As we wean ourselves away from fossil fuels and ramp up our reliance on alternatives, batteries become ever more important for two main reasons. First, we need grid-scale batteries to store excess electricity from time-varying sources such as wind and solar. Second, we use them to power electric vehicles, which we are now producing at the rate of about 15 million a year worldwide. So far, the batt...

Knowing exactly where faults are located is important both for scientific reasons and for assessing how much damage a fault could inflict if it ruptured and caused an earthquake. In the podcast, Rufus Catchings describes how we can use natural and artificial sources of seismic waves to create high-resolution images of fault profiles. He also explains how faults can act as seismic waveguides, an ef...

During the past couple of decades, we have discovered that stars with planetary systems are not rare, exceptional cases, as we once assumed, but actually quite commonplace. However, because exoplanets are like fireflies next to blinding searchlights, they are incredibly difficult to study. Yet, as Sara Seager explains, we are making astonishing progress. Various ingenious methods and the use of po...

We have only a tantalizingly small number of sources of information about the Earth’s deep mantle. One of these comes from the rare diamonds that form at depths of about 650 km and make their way up to the base of the lithosphere, and then later to the surface via rare volcanic eruptions of kimberlite magma. In the podcast, Evan Smith talks about a new class of large gem-quality deep-mantle diamon...

Continental crust is derived from magmas that come from the mantle. So, naively, one might expect it to mirror the composition of the mantle. But our measurements indicate that it does not. Continental crust contains significantly more silica and less magnesium and iron than the mantle. How can we be sure this discrepancy is real, and what do we think explains it? In the podcast, Roberta Rudnick p...

We tend to think of continental tectonic plates as rigid caps that float on the asthenospheric mantle, much like oceanic plates. But while some continental regions have the most rigid rocks on the planet, wide swathes of the continents are not rigid at all. In the podcast, Alex Copley explains how this differentiation comes about and points to evidence that the responsible processes have been oper...

Shanan Peters believes we need to assemble a global record of sedimentary rock coverage over geological time. As he explains in the podcast, such a record enables us to disentangle real changes in the long-term evolution of the Earth-life system from biases introduced by the unevenness and incompleteness of the sedimentary record. To this end, he and his team have established Macrostrat, a platfor...

Complex life did not start in the Cambrian - it was there in the Ediacaran, the period that preceded the Cambrian. And the physical and chemical environment that prevailed in the early to middle Cambrian may well have arisen at earlier times in Earth history. So what exactly was the Cambrian explosion? And what made it happen when it did, between 541 and 530 million years ago? Many explanations ha...

Jupiter's innermost Galilean moon, Io, is peppered with volcanos that are erupting almost all the time. In this episode, Scott Bolton, Principal Investigator of NASA's Juno mission to Jupiter, describes what we're learning from this space probe. Since its arrival in 2017, its orbit around the giant planet has progressively shifted to take it close to Jupiter’s moons and rings. In Decem...

We know that most magma originates in the Earth’s mantle. As it pushes up through the many kilometers of lithosphere to the surface, it pauses in one or more magma chambers or partially melted mush zones for periods of up to a few millennia before erupting. But while we have seismic evidence and models and support this picture, we have not hitherto been able to watch how magma actually moves in th...

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...

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 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, pre...

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 C...

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 u...

At the core of Earth’s geological thermostat is the dissolution of silicate minerals in the presence of atmospheric carbon dioxide and liquid water. But at large scales, the effectiveness and temperature sensitivity of this reaction depends on geomorphological, climatic, and tectonic factors that vary greatly from place to place. As described in the podcast, to predict watershed-scale or global te...

Banded Iron Formations (BIFs) are a visually striking group of sedimentary rocks that are iron rich and almost exclusively deposited in the Precambrian. Their existence points to a major marine iron cycle that does not operate today. Several theories have been proposed to explain how the BIFs formed. While they all involve the precipitation of ferric (Fe3+) iron hydroxides from the seawater via ox...

The geological history of most regions is shaped by a whole range of processes that occur at temperatures ranging from above 800°C to as low as 100°C. The timing of events occurring over a particular temperature range can be recorded by a mineral which crystallizes over that range. The mineral calcite is suitable for recording low-temperature processes such as fossilization, sedimentation, and flu...

In this episode, Martin Van Kranendonk lays out a convincing case for life on Earth going back to at least 3.48 billion years ago. To find evidence for very ancient life, we need to look at rocks that have been largely undisturbed over billions of years of Earth history. Such rocks have been found in the Pilbara region of northwest Australia. As explained in the podcast, the 3.48-billion-year-old...

The Alps are the most intensively studied of all mountain chains, being readily accessed from the geological research centers of Europe. But despite this, there remains considerable uncertainty as to how they formed, especially in the Eocene (about 40 million years ago) when the events that led directly to Alpine mountain-building started. In the podcast, Rob Butler explains how much of this uncer...

The Franciscan Complex is a large accretionary prism that has been accreted onto the western margin of the North American continent. Unlike most such prisms, which are submarine, it is exposed on land, making it a magnet for researchers such as John Wakabayashi. In the podcast, he describes this remarkable complex and explains the mechanisms that may have operated over its 150-million-year history...

How can we tell if the sedimentary record is good enough to make solid inferences about the geological past? After all, it can be difficult, or even impossible, to infer what is missing, or indeed whether anything is missing at all. As he explains in the podcast, Bruce Levell tackles this question by combining fieldwork with systematic analysis based on what we know about contemporary deposition a...