Landscapes Live

Fall 2026 Seminar Series

‼️ You can register for all seminars using this Zoom link:

 https://cuboulder.zoom.us/meeting/register/Sq6Km1gtQVac_bPHqnZ6fw#/registration

Thursday, 29 October 2026 at 16:00 CEST

Julia Carr (Franklin and Marshall College, USA)

TBD

Thursday, November 5 2026 at 16:00 CEST

Sean Gallen (Colorado State University, USA)

Tectonic Geomorphology and Subduction Zone Geodynamics: Lessons from the Calabrian Forearc, Italy

Geomorphology offers an integrated record of deep Earth processes across scales, from landforms to plate boundaries, and across timescales from decades to millions of years. Subduction forearcs preserve interactions among plate motions, mantle flow, and surface processes, yet disentangling their contributions to uplift remains challenging. Here, we use tectonic geomorphology to quantify rock uplift in the Calabrian forearc, a retreating subduction system where slab tearing at ~1-2 Ma produced a narrow, ~250 km-wide plate boundary. Marine terraces record broad anticlinal uplift over ~250 kyr, with maximum rates above the northern and southern slab tears, a pattern flexural isostatic modeling attributes to mantle-driven processes. River profiles and ¹⁰Be erosion rates show uplift accelerating from ~0.2 to ~0.8 mm/yr at ~1.5 Ma, earlier above the torn slab edges. Thirty-million-year uplift histories from three catchments show that uplift does not correlate with subduction velocity: from ~10 to ~1.5 Ma, subduction was fast, but uplift was slow, suggesting that upper-mantle convection and negative buoyancy suppressed uplift until slab fragmentation disrupted it. These results show that slab-mantle dynamics, rather than crustal processes, have governed Neogene-to-present uplift of the Calabrian forearc.

Thursday, November 12 2026 at 16:00 CEST

Paula Snook (Western Norway University of Applied Sciences, Norway)

The exciting detective work behind unstable rock slopes

Unstable rock slopes and slow-moving rockslides are highly varied phenomena: every instability is different, and often very complex. We may first identify an unstable slope by observing open bedrock fractures, daylighting sliding surfaces, rockfall activity, or active displacement in scree or bedrock revealed by techniques such as InSAR. Once a slope is flagged as unstable, the detective work begins. What exactly is unstable? How much movement is occurring? What is driving that movement? And is there a risk of a larger, sudden failure?

Answering these questions requires a combination of well-established methods and site-specific techniques tailored to each slope. Only by integrating different approaches can we understand the processes at work and the factors controlling instability. In this presentation, I will explore two unstable rock slopes in Western Norway that appear so similar at first glance but are yet so different.

Thursday, November 19 2026 at 16:00 CEST

Leonard Sklar (Concordia University, Montreal, Canada)

Sediment grain size: The key variable through which lithology, climate, and tectonics influence landscape evolution

I recently published a review paper making this argument. Here’s the abstract: Earth’s terrestrial topography evolves in response to the interaction of tectonics, climate, and lithology. Recent discoveries suggest that the grain size of sediments produced on hillslopes and transported through river networks is key to understanding these interactions. Hillslope grain size varies systematically with erosion rate and residence time, the degree of chemical and physical weathering, and the fracture density and susceptibility to weathering of rock. Variations in initial grain size strongly influence the spatial evolution of grain size distributions as particles mix and wear during downstream transport through channel networks. In rivers, the size and flux of the coarse fraction of the sediment load control the rate of incision into bedrock and thus govern channel slope and ultimately the relief of actively eroding landscapes. These relationships suggest that a primary way that tectonics, climate, and lithology influence landscape evolution is through their controls on sediment grain size.

In this talk, I’ll share with you highlights from the decades-long research journey that led me to this perspective. I’ll also highlight recent work by others that suggests that the era of seeing landscapes through the lens of stream power may be coming to an end, with a bright future for new insights and understanding enabled by putting sediment grain size at the center of our world view.

Thursday, November 26 2026 at 16:00 CEST

Richard Ott (University of Amsterdam, The Netherlands)

How natural are 'natural' erosion rates? Quantifying human impacts on erosion across space and time

Humans have dramatically altered erosion and sediment transport, but by how much? To answer this, we need to know natural erosion rates. Easy: just measure cosmogenic nuclides in river sediments. But what about areas without measurements? Just calibrate a stream-power model and extrapolate, right? Not so fast. In this talk, I'll explore key limitations of using cosmogenic nuclides to measure and infer natural erosion rates.

Using examples from the Colombian Andes, I'll first show how nonlinear relationships between erosion and channel steepness complicate these predictions, and how incision thresholds may influence mountain-range topography. Comparing our predicted natural erosion rates with modern sediment loads reveals how agriculture, deforestation, and mining have accelerated erosion. 

Next, we'll travel to the Mediterranean to investigate just how 'natural' cosmogenic nuclide-derived erosion rates are in the first place. Using paired in-situ ¹⁴C and ¹⁰Be measurements from Crete, I'll show how millennia of human land use can substantially bias ¹⁰Be erosion estimates, but also how these nuclides can help reconstruct Holocene erosion histories.

Thursday, December 3 2026 at 16:00 CEST

Gaia Stucky de Quay (Massachusetts Institute of Technology, USA)

Early Mars Geomorphology: Lessons and Limits from Earth

Abundant liquid water once flowed across Mars. Yet its volume, timing, and the climatic conditions under which it existed remain difficult to quantify. Relationships calibrated on Earth provide one avenue to determine these quantities. A recently developed terrestrial scaling between lake size and outlet canyon dimensions constrains flood volumes at Martian paleolakes. Similarly, stream power incision models based on Earth can be leveraged on Mars. Using precipitation outputs from Mars paleoclimate models, we build surface discharge maps and test these against observed valley network erosion. The best-fitting scenarios require widespread surface water including a global ocean, with valley formation before the emplacement of Tharsis. However, application of Earth-based techniques to Mars is limited by two key differences from Earth: preservation and resolution. Approximately 3.5 billion years of impact cratering has destroyed a substantial fraction of valley networks, which interpretations of present-day morphometrics must account for. Future work should continue to quantify how the surface has preserved fluvial signals through time. Finally, we address the resolution gap with a new, open-source global digital elevation model, removing the data barrier for future Mars geomorphic studies.

Thursday, 4 December 2025 at 16:00 CEST

Paola Passalacqua (ETH Zurich, Switzerland)

Flows across boundaries: Transport dynamics in shifting landscapes

Now on LL's Youtube page: https://youtu.be/OwWTykkZYYw