Fault Lines

Sixty-six million years ago, at the end of the Cretaceous, a roughly ten-kilometer-wide rock struck the Yucatán while massive volcanic eruptions were already reshaping the Deccan region of India. This episode of Fault Lines asks not only what caused the mass extinction but how fast the killing happened: in hours, over decades, or across millennia.

The hosts compare three clocks: a possible firestorm modeled in the first hour or two, a textbook impact winter lasting years to decades, and the slower pressure of Deccan Traps volcanism. Along the way they look at new evidence on the impactor's rock type and what it may mean for sulfur and climate. They also separate what is measured from what is modeled.

This episode is for anyone curious about the end-Cretaceous extinction who wants to understand which timeline best fits which survivors and victims.

About 201 million years ago, at the end of the Triassic Period, ferns spread across a smoky, overheated land while the oceans were already short of oxygen. This episode of Fault Lines asks what drove the end-Triassic extinction: a fast, sulfur-driven blow, a slow suffocation, or both.

Ola and Amara weigh three 2026 clues against one another: sulfur released by magma that stayed underground, evidence of oxygen-poor oceans in rocks from Alaska, and fern-fuelled wildfires recorded in European pollen and spores. They also separate what the papers state from the hosts' own inference, and note where global versus local signals remain unresolved.

It suits listeners who want to see how evidence for a mass extinction is built and debated, and who want to understand why the answer is still a reading rather than a verdict.

About 539 million years ago, the seafloor was home to soft-bodied organisms in shallow seas, just before shelled animals, spines, and eyes appear in the fossil record of the Cambrian period.

Was the so-called Cambrian explosion a real burst of evolution, or an artifact of which animals fossilize? Hosts Amara and Ola weigh the evidence, including the Jiangchuan Biota from China, a molecular-clock study suggesting a more drawn-out radiation, and three contested triggers: brain evolution, the "faecal revolution," and rising oxygen. They also note where the sources stop short.

This episode is for listeners curious about early animal evolution who want to understand how fossil preservation shapes the story, and why the word "explosion" may deserve an asterisk.

About 4,500 million years ago, during the Hadean Eon, Earth was a glowing, partly molten ball of rock when a Mars-sized body called Theia struck it.

The episode asks whether new simulations showing a Moon-sized body forming in about five hours overturn the giant impact story or simply add a conditional branch to it.

Topics include the September 2026 simulations that add rock strength and test three pre-impact temperature cases, iron isotope evidence that Theia likely formed in the inner Solar System, and the two lower-mantle blobs that may be Theia relics.

This episode is for listeners curious about lunar origins who want to understand which evidence separates fast and slow Moon formation, and which evidence cannot.

Before the Great Oxidation Event, roughly 2,450 million years ago in the Paleoproterozoic era, Earth had an orange, hazy sky, sulfur-rich air unfit to breathe, and oceans tinted purple by dissolved iron. This episode asks how firm the textbook version of that transformation really is, and how much oxygen actually accumulated. Discussion covers a 2026 University of Victoria study linking a carbon-13 isotope spike to the event's timing, a Crockford-led review showing oxygen estimates spanning orders of magnitude, and additional phosphorus and productivity-based proxies with their own unresolved uncertainties. Listeners interested in early Earth history will come away understanding why the scale of the Great Oxidation Event is widely accepted while the specific numbers remain actively debated.

Roughly 200 million years ago, during the late Triassic, Earth's landmasses were locked together in the single supercontinent Pangaea; a billion years earlier, an even older supercontinent called Rodinia had already formed and broken apart. This episode traces how scientists went from denying continents move at all to debating how many times supercontinents have assembled and split. It covers Alfred Wegener's original 1912 Frankfurt lecture, the 1926 New York symposium often blamed for killing continental drift, and two overlooked 1932 GSA Bulletin papers that actually sealed its rejection for decades. The hosts also preview GSA Connects 2026 in Denver, where sessions on Rodinia and the Wilson cycle pick up the argument a century later. Listeners will come away understanding why a scientific idea's death and revival rarely happens the way textbooks tell it.

Roughly 717 million years ago, Earth's tropics vanished beneath ice kilometers thick, transforming the planet into a near-total snowball during the Cryogenian period. This episode asks how the Sturtian glaciation could have lasted 56 million years without breaking, a duration that initially defied standard climate models. Discussion covers the Harvard-led carbon-cycle mechanism involving basalt weathering and the Franklin igneous province, layered rock evidence from Scotland's Garvellach Islands suggesting rhythmic freeze-thaw cycles rather than static ice, and the contrast with the shorter, four-million-year Marinoan glaciation that followed. Listeners will come away understanding how scientists reconstruct ancient climate extremes and why the Sturtian's length and internal variability may have shaped the trajectory of early life on Earth.

A narrow Himalayan valley on the Nepal-Tibet border, quiet enough to hear a yak bell, is erased in minutes when a wall of mud, ice, and bedrock breaks loose from Langtang Lirung and travels nearly one hundred kilometers. This episode asks whether a 2026 glacial lake outburst flood follows the same mechanics as the deep-time megafloods the show usually reconstructs from rock layers, like the Ice Age draining of Lake Missoula and the Zanclean flood that refilled the Mediterranean roughly 5.3 million years ago. Discussion covers the USGS satellite reclassification from moraine failure to bedrock-and-ice collapse, Langtang Lirung's repeat-failure history, and the exposure of millions living beneath similar lakes across High Mountain Asia. Listeners will walk away understanding how ancient flood geology helps explain a disaster unfolding in real time.

Fifty million years ago, during the Eocene, Earth was a warmer world with crocodiles near the poles and a magnetic field that was anything but calm. This episode asks whether the geological record of geomagnetic reversals is actually complete, or if entire flips of Earth’s magnetic field are missing from the story scientists tell. Along the way, the hosts examine ultra-slow reversals lasting up to 70,000 years, new evidence for uncounted reversals in Ethiopian basalts and statistical patterns after superchrons, and recent satellite data showing a surprising change in core flow beneath the Pacific since 2010. Listeners come away with a grounded sense of how the geodynamo behaves over millions of years, what that means for the reliability of today’s magnetic shield, and how confidently we can read Earth’s magnetic past during the Eocene, roughly 34–56 million years ago.

On March 28, 2025, a security camera outside Mandalay recorded the ground itself tearing sideways, 2.5 meters of slip along Myanmar's Sagaing fault in roughly two seconds, the same fault system born from the India-Eurasia collision some 50 million years ago. This episode asks whether fault rupture is governed by predictable physics or reconstructed after the fact through hindsight. Ola and Amara unpack the supershear "sonic boom" that outran the earthquake's own shear waves, its eerie parallel to the 1906 San Francisco quake, and a new stress study suggesting California's Mojave South segment and Cajon Pass sit at a thousand-year stress high. Listeners will come away understanding why seismologists still struggle to forecast where and how faults actually break.