Erosion of the Santa Monica Mountains, California

The Santa Monica Mountains are adjacent to the Los Angeles metropolitan area in southern California and began forming ~5–7 million years ago. The mountains were built along faults, and fault movement can trigger earthquakes, which pose significant, and potentially catastrophic hazard to the LA region. Geologically speaking, it is difficult to constrain the rate at which faults rupture because they are active over time scales longer than human records. However, mountains being pushed up along the faults are also being worn down by river basin erosion and measuring erosion of river basins over geologically relevant timescales is straightforward. This project assesses the spatial pattern of erosion rates of >20 river basins in the Santa Monica Mountains and relate them to uplift rates across the Malibu coast. It has been a work in progress since 2016, but is nearing completion.

Status: Awaiting final data

Participants & Collaborators:

• Assoc. Prof. Sean Gallen, Colorado State University

• Dr. Kirk F. Townsend, California State Geological Survey

• Community Cosmogenic Facility @ University of Vermont

• PRIME Lab @ Purdue University

• Prof. Nathan Niemi, University of Michigan

• Prof. Marin Clark, University of Michigan

Funding Sources: 

• Eastern Michigan University, GameAbove College of Arts and Sciences Dean’s Faculty Professional Development Award: Acquiring geomorphological data for dating Ice sheet retreat in Michigan and measuring erosion rates in California’s Santa Monica Mountains (2024)

• NSF (Award #1939000): RUI: Quantifying the effects of wildfire burning on 10Be concentrations in river sand - A case study of the 2018 Woolsey Fire, Santa Monica Mountains, CA (2020-2023)

• Purdue Rare Isotope Measurement Laboratory (PRIME Lab), Seed Grant, Co-PI, Fault slip rates of the Santa Monica Mountains, California, reflected in 10Be erosion rates (2017)