The Hit and Run Rockies - With Professor Basil Tikoff

Episode Overview

• The hosts introduce the monumental and scientifically debated topic of how the Rocky Mountains formed, welcoming expert guest Dr. Basil Tikoff to discuss the challenges.
• The conversation establishes fundamental geological concepts like stress, strain, and transpression to build a foundation for understanding complex tectonic models.
• The episode contrasts the traditional "flat-slab subduction" theory with Dr. Tikoff's innovative "Hit-and-Run" model, which proposes an oblique collision and subsequent lateral movement.
• A central theme is how the Hit-and-Run model explains deformation far inland by proposing that stress was transmitted through the strong mantle, not the weaker crust.
• The discussion explores the nature of scientific progress, showing how new evidence like mantle tomography can challenge established consensus and force a re-evaluation of long-held beliefs.

Key Concepts

• Stress vs. Strain: A foundational distinction is made between stress (the force applied per unit area on a rock) and strain (the resulting, observable deformation of the rock). Geologists measure strain in the field.
• Transpression: A type of tectonic movement where rocks are simultaneously sliding past each other (like the San Andreas Fault) and being compressed, often forcing material upward.
• Flat-Slab Subduction Model: The long-held traditional theory for the Rockies' formation, which posits that an oceanic plate subducted at an unusually shallow angle far underneath the North American continent.
• Hit-and-Run Model: The alternative model proposing a two-phase process: an initial oblique "hit" by an oceanic plateau, followed by a "run" phase where the terrain moves northward along the continental margin.
• Stress Transmission via Mantle Lithosphere: A core mechanism of the Hit-and-Run model, suggesting that collisional stress was transmitted hundreds of kilometers inland through the strong, rigid mantle, bypassing the weak, "squishy" crustal arc at the edge of the continent.
• Modern Analogues: The discussion uses modern geological examples, such as the Altiplano in the Andes and the India-Asia collision (which formed Lake Baikal), to illustrate the principles of high plateau formation and long-distance stress transfer.
• Mantle Tomography Evidence: New geophysical data that images the Earth's mantle fails to show evidence of a remnant flat slab, posing a significant challenge to the traditional model and supporting the search for alternatives.

Quotes

• At 1:06 - "Oh no, I could take him. I'm a lot meaner." - Host Chris explains his reasoning for being the likely winner in a hypothetical teacher fight club, showcasing the hosts' lighthearted banter.
• At 1:51 - "It's just a... it's monumental. We could interview so many people and do a huge series actually on the Rocky Mountains." - Chris explains why the podcast has been hesitant to cover the formation of the Rocky Mountains due to the topic's complexity.
• At 2:06 - "I flat out asked Basil, could you teach an hour-long lecture on the formation of Rockies? And he's like, 'I wouldn't want to do that... there's so much that we don't know and I couldn't do it in that limited time frame.'" - Chris shares guest expert Basil Tikoff's view on the difficulty of summarizing the topic.
• At 22:33 - "This is an exact prediction of a model." - Basil Tikoff explains that seemingly contradictory geological observations he made during his PhD were actually a perfect real-world confirmation of a theoretical structural model.
• At 24:55 - "There is no manifestation of stress in a rock. The manifestation of in the rock is strain." - Basil Tikoff clarifies the crucial difference between the theoretical force (stress) and the physical, measurable deformation (strain).
• At 49:33 - "Why isn't all that stress accommodated by the... why don't you just squish the arc out of existence as opposed to like all this deformation 500, 1000 kilometers inboard?" - A host poses the critical question that challenges traditional models and which the Hit-and-Run model aims to answer.
• At 50:13 - "The strength is in the mantle... and the mantle can transmit that. There is no way stress can be transmitted through a crust in that way." - Basil Tikoff provides the central mechanism of the Hit-and-Run model, explaining how stress traveled so far inland.
• At 51:13 - "It's kind of like a tailback gets the ball and just a violent collision at the line of scrimmage... and so the tailback then stays up and just bounces it laterally to the side, to the outside. Hit and run." - A host offers a football analogy to help visualize the oblique collision and lateral movement of the Hit-and-Run model.
• At 55:16 - "If I'm wrong about the Hit-and-Run, it's because I'm not being mobilist enough. It's not that I'm being too crazy, I'm not being crazy enough." - Basil Tikoff reflects that the true tectonic movements might have been even more dynamic than his model proposes.
• At 58:08 - "The best technique you have for finding a slab is tomography, and it's not there. That's a problem." - Basil Tikoff points out a major flaw in the flat-slab hypothesis: modern geophysical imaging does not show evidence of the slab where it should be.
• At 59:52 - "You don't have slabs and shallow slabs under continents. What we have are slab walls. And they go for thousands of kilometers." - Basil Tikoff describes what modern mantle tomography actually reveals—massive, vertical slab walls, not the gently-dipping slabs previously hypothesized.
• At 67:41 - "'There is a church of the Laramide, and I'm part of that church.' That's her term. 'And I just can't, will never be able to see it in that other way.'" - Basil Tikoff quotes a colleague to illustrate the deeply entrenched nature of the traditional model and the scientific community's resistance to new ideas.

Takeaways

• The formation of major geological features like the Rockies is not settled science; it remains a field of active and significant scientific debate.
• To understand complex geology, it is critical to distinguish between stress (the applied force) and strain (the resulting, observable deformation in the rock).
• Stress can be transmitted over vast distances through strong, rigid parts of the Earth, such as the mantle lithosphere, which can explain deformation occurring far from a plate boundary.
• Seemingly contradictory field observations can be the key to confirming a more complex, unifying theory that accounts for all the data.
• New technologies and data, such as mantle tomography, are essential tools that can fundamentally challenge and even overturn long-standing scientific models.
• Scientific progress often faces resistance from established consensus, demonstrating the human element and intellectual inertia in the advancement of knowledge.
• Using modern geological settings as analogues is a powerful method for developing and testing hypotheses about ancient tectonic events.
• A good scientific model must not only explain existing evidence but also address inconsistencies and paradoxes that older models cannot, such as why deformation occurred so far inland.