Sam A Johnstone
Sam uses geologic mapping and computational methods to characterize and understand earth’s history.
Sam’s primary work is part of the National Geologic Synthesis project, where he works to develop geoinformatics-inspired solutions to integrating and synthesizing geologic data characterizing the nation’s geology. In this work Sam is interested in developing databases and software tools that can facilitate wide-ranging geologic assessments and studies of national scope. Sam is also engaged in efforts to conduct geologic mapping focused on Quaternary deposits (including machine-learning aided mapping of these deposits) and in developing statistical and simulation models to explore geochronology and topographic data.
Prior to starting at the USGS, Sam obtained his PhD from Stanford University in 2016. There he studied how sediment transport and erosion processes shaped hillslopes and river networks. In 2011 Sam obtained his MSc from UC Santa Cruz, where he had also obtained my BS a few years earlier. It was at UC Santa Cruz that Sam first got excited about geologic mapping and where he developed an interest in programming and using low temperature thermochronology to study histories of faulting.
Education and Certifications
Stanford University, PhD in Geology
UC Santa Cruz, MS in Geology
UC Santa Cruz, BS Earth Science
Science and Products
Coexisting seismic behavior of transform faults revealed by high-resolution bathymetry Coexisting seismic behavior of transform faults revealed by high-resolution bathymetry
Dilution and propagation of provenance trends in sand and mud: Geochemistry and detrital zircon geochronology of modern sediment from central California (U.S.A.) Dilution and propagation of provenance trends in sand and mud: Geochemistry and detrital zircon geochronology of modern sediment from central California (U.S.A.)
A stratigraphic approach to inferring depositional ages from detrital geochronology data A stratigraphic approach to inferring depositional ages from detrital geochronology data
A supervolcano and its sidekicks: A 100 ka eruptive chronology of the Fish Canyon Tuff and associated units of the La Garita magmatic system A supervolcano and its sidekicks: A 100 ka eruptive chronology of the Fish Canyon Tuff and associated units of the La Garita magmatic system
Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA
Interpretation of low‐temperature thermochronometer ages from tilted normal fault blocks Interpretation of low‐temperature thermochronometer ages from tilted normal fault blocks
Controls on submarine channel-modifying processes identified through morphometric scaling relationships Controls on submarine channel-modifying processes identified through morphometric scaling relationships
Sediment unmixing using detrital geochronology Sediment unmixing using detrital geochronology
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
Coexisting seismic behavior of transform faults revealed by high-resolution bathymetry Coexisting seismic behavior of transform faults revealed by high-resolution bathymetry
Dilution and propagation of provenance trends in sand and mud: Geochemistry and detrital zircon geochronology of modern sediment from central California (U.S.A.) Dilution and propagation of provenance trends in sand and mud: Geochemistry and detrital zircon geochronology of modern sediment from central California (U.S.A.)
A stratigraphic approach to inferring depositional ages from detrital geochronology data A stratigraphic approach to inferring depositional ages from detrital geochronology data
A supervolcano and its sidekicks: A 100 ka eruptive chronology of the Fish Canyon Tuff and associated units of the La Garita magmatic system A supervolcano and its sidekicks: A 100 ka eruptive chronology of the Fish Canyon Tuff and associated units of the La Garita magmatic system
Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA Establishing chronologies for alluvial-fan sequences with analysis of high-resolution topographic data: San Luis Valley, Colorado, USA
Interpretation of low‐temperature thermochronometer ages from tilted normal fault blocks Interpretation of low‐temperature thermochronometer ages from tilted normal fault blocks
Controls on submarine channel-modifying processes identified through morphometric scaling relationships Controls on submarine channel-modifying processes identified through morphometric scaling relationships
Sediment unmixing using detrital geochronology Sediment unmixing using detrital geochronology
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.