EPSS Colloquium - spring-2024
Chicxulub, Deccan, Tanis, and the Demise of T. rex and Friends
April 2, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Mark Richards - U Washington
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The Deccan Traps flood basalt eruptions were approximately time-coincident with the Chicxulub impact in Yucatan, Mexico, which was likely the main cause of the end-Cretaceous (K-Pg) mass extinction that exterminated the non-avian dinosaurs at about 66 Ma. The Deccan eruptions were well underway at K-Pg time, but geological and geochronological evidence suggests that the magnitude Mw ~11 earthquake due to Chicxulub may have accelerated the Deccan eruptions at exactly K-Pg time. Although it is unlikely that outgassing associated with the Deccan eruptions was primarily responsible for the mass extinction, it is possible that these eruptions contributed to the climate disturbance that resulted in a prolonged recovery period. Recently, a remarkable paleontological discovery in North Dakota, suggests that seismic waves from the Chicxulub impact also caused a tsunami-like deposit along the existing Western Interior Seaway, capturing literally the last ~2 hours of the Cretaceous (or the first 2 hours of the Paleocene, depending on your point of view) in stroboscopic detail, including freshwater fish ingesting impact spherules from the water column before they were killed by ~10-meter water surges up a large river channel. Modeling and understanding the nature of this event, and likely similar events worldwide, promises to advance our understanding of the K-Pg mass extinction event. The excitation of Deccan eruptions by the Chicxulub impact likewise lacks detailed explanation. In other words, we have new and tantalizing clues as to events at K-Pg time that are perhaps much richer than previously imagined.
Collapse and Ejection in the N-body problem and the Formation of Rubble Pile Asteroids
May 7, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Dan Scheeres - U. Colorado
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Rubble pile asteroids are thought to form in the aftermath of cataclysmic collisions between proto-planets. The details of how the detritus from such collisions reaccumulate to form these bodies are not well understood, yet can play a fundamental role in the subsequent evolution of these bodies in the solar system. Simple items such as how particle sizes and porosity is distributed within a body can have a significant influence on how they subsequently evolve. Current space missions are just starting to gain limited insight into these fundamental questions, but require a better theoretical understanding to fully explain their observations. This work studies how the initial energy and angular momentum of a random collection of gravitating bodies is partitioned and redistributed between escaping components and bound multiple body systems. A generic initial distribution of N bodies will naturally lose many components due to multi-body dynamical interactions. If the bodies have finite density, some components will also form condensed distributions, becoming single, binary or multiple component rubble pile asteroids. We derive and apply rigorous results from the Full N-body problem to place limits and constraints on how the energy and angular momentum of such systems can evolve, which controls the formation of stable rubble pile asteroids.
Climate as seen through the lens of Colorado’s Glaciers
May 14, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Bob Anderson - Dept of Geological Sciences, University of Colorado
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Over the last couple million years, glaciers in Colorado and the American West have come and gone to the pace of global climate history. Only 20 thousand years ago we had many glaciers in the state, flowing down the valleys of nearly every mountain range. Yet very few features we would recognize as glaciers now exist in our mountains. I will introduce the history of climate and will discuss what has driven that history over this latest cycle of the ice ages. I will then focus on our own glaciers and how we have come to know their more recent history – chiefly their demise since the last glacial maximum 20 thousand years ago. I will then focus on the hundreds of odd glaciers that now dot our mountain valleys. These “rock glaciers” are cloaked with a layer of rocks that serves as something of a parasol to protect them from the heat, and at the same time prevent them from being recognized as glaciers. We are only now coming to understand how these glaciers work. I will show that a combination of modern speeds from feature tracking and exposure ages from 10Be concentrations constrains tightly the Holocene climate history of our mountains. Finally, I will use these rock glaciers to document the importance of lateral erosion of the headwalls, generating strong asymmetry of these ranges.