ABOUT MY RESEARCH
My research group and I work at the intersection of geomorphology, biogeochemistry, hydrology, and Earth history. We study linkages between tectonics, topography, erosion, rock structure, hydrology, and weathering, aiming to understand how they conspire to shape the landscapes at Earth's surface; how they regulate water and biogeochemical cycles, and thus life on this planet; and how they contribute to natural hazards, particularly landslides and debris flows.
Much of my work has focused on the modern and ancient carbon cycle, and particularly how erosion and surface processes affect exchanges of carbon between atmosphere, water, organic material and rocks. This movement of carbon ultimately controls Earth's climate.
While carbon has been a central focus of my research, I am motivated by a wide range of problems, from Earth history to water and biogeochemical resources to geohazards. These at once call to basic intellectual curiosity and simultaneously hold promise of knowledge vital to humanity’s future. I want to understand how Earth came to be the planet we know today, why it has remained habitable over hundreds of millions of years, and what has caused changes in the global environment over this time.
At the same time, my research provides knowledge to inform sustainable management of natural resources, and I am interested in what we can learn from Earth’s present and past about global change as well as the cycling of life-sustaining water and nutrients.
Increasingly, I have turned attention to how understanding of Earth’s landscapes can help prediction of natural hazards, and to using novel combinations of tools (such as shallow geophysics coupled with stable water isotopes) to understand water pathways in mountainous terrain which are critical for sustaining freshwater supply.
To address these problems, my group combines challenging fieldwork, cutting-edge laboratory analyses and experiments, remote sensing, and modeling across spatiotemporal scales. Many of my projects have been generously supported by the US National Science Foundation.
Much of my work has focused on the modern and ancient carbon cycle, and particularly how erosion and surface processes affect exchanges of carbon between atmosphere, water, organic material and rocks. This movement of carbon ultimately controls Earth's climate.
While carbon has been a central focus of my research, I am motivated by a wide range of problems, from Earth history to water and biogeochemical resources to geohazards. These at once call to basic intellectual curiosity and simultaneously hold promise of knowledge vital to humanity’s future. I want to understand how Earth came to be the planet we know today, why it has remained habitable over hundreds of millions of years, and what has caused changes in the global environment over this time.
At the same time, my research provides knowledge to inform sustainable management of natural resources, and I am interested in what we can learn from Earth’s present and past about global change as well as the cycling of life-sustaining water and nutrients.
Increasingly, I have turned attention to how understanding of Earth’s landscapes can help prediction of natural hazards, and to using novel combinations of tools (such as shallow geophysics coupled with stable water isotopes) to understand water pathways in mountainous terrain which are critical for sustaining freshwater supply.
To address these problems, my group combines challenging fieldwork, cutting-edge laboratory analyses and experiments, remote sensing, and modeling across spatiotemporal scales. Many of my projects have been generously supported by the US National Science Foundation.
Major research themes
Understanding the natural processes that produce and sustain water and soil resources |
Developing and applying isotopic proxies to understand past changes in global biogeochemical cycles |
Interactions between life, weathering, and the carbon cycle — from microbes to forested ecosystems to global biogeochemical cycling |
SOME EXAMPLES of RECENT AND ONGOING RESEARCH PROJECTS
Erosion of permafrost riverbanks in the Yukon River Basin and implications for water quality
This collaboration with the Caltech Surface Processes Group and the Yukon River Inter-Tribal Watershed Council is looking at how riverbank erosion is changing as permafrost thaws in a warming climate. Our group is focusing on the consequences for water quality, including release of contaminants such as mercury from permafrost, as well as the implications for carbon release. See more info at: arcticrivers.caltech.edu/ This research is supported by the NSF Navigating the New Arctic program. |
Exhumation, erosion, weathering and hydrology in the Himalaya of central Nepal
This project, supported by the NSF Frontier Research in Earth Sciences Program, involves researchers from 5 universities working together to understand how steep, actively-growing mountains sustain natural resources, generate natural hazards, and regulate the global carbon cycle. The project is focused on the Melamchi Valley, which is located to the northeast of Kathmandu and spans a dramatic gradient in topography and erosion rates from the Middle Hills to the High Himalaya of central Nepal. See more info at: sites.google.com/usc.edu/nepal-fres/research |
Cascading hazards and landscape evolution: Wenchuan Earthquake, Gorkha Earthquake, Melamchi Floods, Bobcat Fire, and more
My group has been working on catastrophic geomorphic events that range from massive numbers of earthquake-triggered landslides to devastating floods such as the 2021 Melamchi Flood, shown in the figure here. Building on this work, I am involved in a collaborative community effort to develop a Center for Land Surface Hazards; more info here: www.geoclash.org/ |
Hydrology and Biogeochemistry across the Andes-Amazon transition
I have worked for over a decade on the fluxes and cycling of water, sediment, and carbon across the transition from the Andes Mountains to the Amazon floodplain in the Rio Madre de Dios watershed of Peru. This has been part of a collaboration with the Andes Biodiversity and Ecosystems Research Group and USC colleague Sarah Feakins. Support has come from multiple grants from the US National Science Foundation. More recently, my work has turned attention to the effects of alluvial gold mining in this region. |
Southern California Plasma Lab
Together with USC colleagues Seth John and Emily Cooperdock, I am one of the PIs on the USC PLASMA Facility which provides my group — and many others — with the state-of-the-art analytical capabilities for making measurements of natural samples that help us to answer our motivating scientific questions. See here: sites.google.com/usc.edu/usc-plasma-facility/home |