DIRT-Lab: Earth Surface Processes Research
Geomorphology and Geochemistry research led by Dr. Jean Dixon
Dear prospective graduate students, I will not be taking on new students in my research group for the 2024-2025 academic year.
We study soil DIRT (and other things like dirty streams, dirty plants, dirty ice, and dirty snow).
The Earth Surface Group studies the chemical and physical evolution of Earth's soils and surface, using a diverse range of geochemical, remote sensing, geophysical, and field methods. In addition to computing lab and field supply space, we have two major lab facilities at MSU.
- Cosmogenic-Radionuclide (CRN) Preparation Facility
- This facility is used to prepare soil and sediment samples for cosmogenic isotope analysis. These rare isotopes serve as clocks that record the time spent near the surface by Earth materials, and can be used to derive soil or landscape erosion rates that average over thousand to million year time scales. This facility includes two processing laboratories, which host acid digestion hoods, laminar flow clean benches, ultrapure water, centrifuges, and high-resolution analytical balance.
- Gamma-Spectroscopy Lab
- This facility includes two high-resolution, broad energy germanium (BEGe) detectors that measure gamma radiation of fallout radionuclides. These isotopes are produced in the atmosphere and deposited at the surface where they can be used to track soil and sediment movement. By measuring their natural radioactivity, we can record soil and sediment processes averaged over the scale of an individual storm event (7Be), a few decades (137Cs), or upwards of a hundred years (210Pb).
Earth Surface Research at Montana State University
Geomorphic change in Permafrost Environments
High-latitude permafrost soils store over half the belowground terrestrial organic
carbon pool and are thawing dramatically in response to recent warming. Though permafrost
degredation can drive carbon release, ground instability, and disruption to human
and ecological communities, surprisingly little is known about the geomorphorphic
processes that built and modified these systems over millenial timescales. This project,
with PhD student Zena Robert and Dr. Stephanie Ewing in the Land Resources and Environmental Science Department, uses novel isotopic tracers
of soil erosion, land surface age, and ice residence times to quantify the feedbacks
by which permafrost is created, sustained, and transformed.
Controls on sediment movement in fire-dominated landscapes
The pace, processes, and pathways by which sediment moves across slopes and downstream
through river networks represents the system's sediment connectivity. In this NSF-funded
work in Montana's Bitterroot and Sapphire Mountains, we measure the ways streams and
slopes communicate, and the role of fire and vegetation on sediment storage and erosion
The influence of climate and topography on chemical weathering rates
Chemical weathering converts bedrock to soil, releases rock-derived nutrients to ecosystems,
sequesters atmospheric carbon dioxide, and plays an integral role in shaping Earth's
surface. Current work along the south island of New Zealand and in the Bitterroot
basin of Montana explores how climate and topography represent fundamental controls
on soil weathering and the exposure of bedrock in mountain systems.
Holocene erosion the gates of Yellowstone National Park
Glaciers leave a imprint on the landscape that lasts long after the ice recedes. This
topographic forcing influences the geomorphic processes that alter hillslopes and
rivers, and understanding past change can inform modern hazards. We study the impact
of deglaciation and Holocene environmental change at the northern edge of Yellowstone
National Park, a system where over two million visitors a year traverse dramatic incising
rivers and even active landslides.
Developing isotope proxies of erosional and climatic change
Understanding how landscapes evolve under changing climates is critical in this time of extreme environmental change. Paleorecords (such as lake cores) provide insight into how ecosystems and landscapes responded to past climate changes. To this end, we are testing new applications of meteoric Be-10 in lake systems. This cosmogenic isotope is increasingly used to derive soil ages, but may also be a powerful proxy of past environmental changes in aridity, precipitation, and dust fluxes. Our project compares this isotope system to other known proxies of environmental and geomorphic change from lake sediments from the Greater Yellowstone Ecosystem.