Harrison Gray, Ph.D
Earth's surface is shaped by the transfer of sediment across time and space. As we live on the Earth's surface, understanding this transport of sediment is key to the well-being of our species. I work on solving problems asscociated with landscapes and sediment transport using the tools of computer landscape evolution modeling and the trapped-charge phenomena known as luminescence.
Education and Certifications
Ph.D Geomorphology, University of Colorado - Boulder, 2018
M.S. Geology, Univeristy of Cincinnati, 2013
B.S. Earth Sciences, University of California - Santa Cruz, 2010
Honors and Awards
Presidential Early Career Award for Scientists and Engineers (PECASE), 2025
Science and Products
Earthquake Geology and Paleoseismology Overview
The goals of USGS earthquake geology and paleoseismology research are 1) to make primary observations and develop ideas to improve our understanding of the geologic expression of active faulting, and 2) to acquire data that will improve the National Seismic Hazard Model. Geological research allows us to characterize faults, including the identification of secondary seismogenic structures, to study...
Quaternary Hydroclimate Records of Spring Ecosystems
Desert springs and wetlands are among the most biologically productive, diverse, and fragile ecosystems on Earth. They are home to thousands of rare, endemic, and endangered plants and animals and reflect the availability and health of emergent groundwater. Despite the ecological importance of these wetlands, our knowledge of how they might respond to future environmental conditions is limited...
Western Basin & Range - Eastern California Shear Zone
The Eastern California Shear Zone (ECSZ) Mapping project, funded by the National Cooperative Geologic Mapping Program, combines surficial and bedrock geologic mapping, geophysical surveys, and high-resolution topographic data analysis with neotectonic, geomorphic, structural, volcanic, and geochronologic studies to better understand the tectonic framework and landscape evolution of the ECSZ in the...
Filter Total Items: 14
Luminescence Data For Floodplain Carbon Storage: Soil Organic Carbon, Surface Age, and Vegetation in an Icy River Corridor Luminescence Data For Floodplain Carbon Storage: Soil Organic Carbon, Surface Age, and Vegetation in an Icy River Corridor
Rivers are some of the most dynamic features of the Arctic landscape, yet their role in the global carbon cycle is poorly understood. Researchers are still unraveling the intricacies of how river dynamics control organic carbon (OC) accumulation, transport, and degradation in riverine systems. The interplay between permafrost thermal state in river corridors, snow and ice-affected...
Data Release for Timing and Abandonment of the Chemehuevi Formation: a Conspicuous Pleistocene Sedimentary Deposit of the Lower Colorado River Data Release for Timing and Abandonment of the Chemehuevi Formation: a Conspicuous Pleistocene Sedimentary Deposit of the Lower Colorado River
This data release contains data for the associated publication: Timing and Abandonment of the Chemehuevi Formation: a Conspicuous Pleistocene Sedimentary Deposit of the Lower Colorado River
Data Release for Luminescence: Neotectonic Mapping of Puerto Rico Data Release for Luminescence: Neotectonic Mapping of Puerto Rico
This report details the luminescence ages and characteristics of four (4) samples that were collected by Jessica Jobe and Rich Briggs of the USGS. These samples are from Holocene and Pleistocene sediments offset by a fault that is exposed in a road cut. The roadcut is in Puerto Rico at 18.003828 and -67.140249 with an elevation of 13.5 m. The sample depths from the modern surface varied...
Datasets documenting neotectonic mapping of Puerto Rico Datasets documenting neotectonic mapping of Puerto Rico
This data release documents neotectonic mapping of fault-related features on high-resolution lidar-derived topography, data documenting an exposure of the South Lajas fault, and summary information for active and potentially active Quaternary faults on the island of Puerto Rico. The data documenting the exposure of the South Lajas fault include detailed unit descriptions, radiocarbon...
Data release for Independent age estimates resolve the controversy of ancient human footprints at White Sands Data release for Independent age estimates resolve the controversy of ancient human footprints at White Sands
Human footprints at White Sands National Park, New Mexico, USA, reportedly date to between ~23,000 and 21,000 years ago according to radiocarbon dating of seeds from the aquatic plant Ruppia cirrhosa. These ages remain controversial because of potential old carbon reservoir effects that could compromise their accuracy. We present new calibrated 14C ages of terrestrial pollen collected...
Geochronologic and isotopic data for Paleohydrologic history of Pluvial Lake San Agustin, New Mexico Geochronologic and isotopic data for Paleohydrologic history of Pluvial Lake San Agustin, New Mexico
This dataset includes tables of radiocarbon, uranium thorium series, and luminescence geochronologic ages and stable carbon and oxygen isotope compositions for sedimentary and organic samples.
Filter Total Items: 28
Spatiotemporal variations in strain release and seismic rupture in multifault systems: An example from Panamint Valley, southeastern California Spatiotemporal variations in strain release and seismic rupture in multifault systems: An example from Panamint Valley, southeastern California
Geometrically complex, multifault ruptures have been observed in recent, damaging earthquakes in southeastern California, sparking renewed efforts to identify physical conditions that promote or inhibit fault discontinuity-spanning coseismic ruptures. The likelihood of ruptures propagating across fault discontinuities is thought to be partly controlled by fault geometries, rupture...
Authors
Aubrey LaPlante, Christine Regalla, Israporn Sethanant, Shannon A. Mahan, Harrison J. Gray
Evidence for nonlocal sediment transport on hillslopes from fault scarp morphology Evidence for nonlocal sediment transport on hillslopes from fault scarp morphology
Hillslope sediment transport processes such as bioturbation, rainsplash, and granular mechanics occur across the entire planet. Yet, it remains uncertain how these small-scale processes act together to shape landscapes. Longstanding hillslope diffusion theory posits that hillslope processes are spatially limited, whereas new concepts of nonlocal sediment transport argue otherwise...
Authors
Harrison J. Gray, Tyler Doane, Sylvia R. Nicovich, Christopher DuRoss, Ryan D. Gold
Timing and geometry of the Chemehuevi Formation reveal a late Pleistocene sediment pulse into the Lower Colorado River Timing and geometry of the Chemehuevi Formation reveal a late Pleistocene sediment pulse into the Lower Colorado River
The Chemehuevi Formation is a distinctive 50−150-m-thick wedge-shaped Pleistocene sedimentary unit deposited by the Colorado River. It lines the perimeters of the river’s floodplains and bedrock canyons for more than 600 km between the mouth of the Grand Canyon and the delta region in the Gulf of California. The formation is composed of a basal tan to light-yellowish-brown and pale...
Authors
Harrison J. Gray, Kyle House, Adam M. Hudson, Jorge A. Vazquez, Ryan S. Crow, Miriam Primus, Shannon A. Mahan, Tammy M. Rittenour, Keith A. Howard
Neotectonic mapping of Puerto Rico Neotectonic mapping of Puerto Rico
Puerto Rico is part of the Puerto Rico-Virgin Islands microplate, along the Caribbean–North American plate boundary between the Puerto Rico trench subduction zone and the Muertos Trough incipient subduction zone. Despite recent seismicity and geodetically constrained deformation of ~3 mm/yr of left-lateral shear across the island, Quaternary fault locations remain largely uncertain...
Authors
Jessica Ann Thompson Jobe, Richard W. Briggs, K. Stephen Hughes, J. Joyce, Ryan D. Gold, Shannon A. Mahan, Harrison J. Gray, Laura E. Strickland
The geochronology of White Sands Locality 2 is resolved The geochronology of White Sands Locality 2 is resolved
Rhode et al. (2024) allege that there are many “unresolved issues” with the geochronology of White Sands National Park (WHSA) Locality 2. They suggest there are substantial age offsets due to hard-water effects in the aquatic plants that were dated and that radiocarbon ages of pollen may be anomalously old due to reworking. In their view, the luminescence ages are likely to be maximum...
Authors
Jeffrey S. Pigati, Kathleen B. Springer, Harrison J. Gray, Matthew R. Bennett, David Bustos
High-resolution geophysical and geochronological analysis of a relict shoreface deposit offshore central California: Implications for slip rate along the Hosgri fault High-resolution geophysical and geochronological analysis of a relict shoreface deposit offshore central California: Implications for slip rate along the Hosgri fault
The Cross-Hosgri slope is a bathymetric lineament that crosses the main strand of the Hosgri fault offshore Point Estero, central California. Recently collected chirp seismic reflection profiles and sediment cores provide the basis for a reassessment of Cross-Hosgri slope origin and the lateral slip rate of the Hosgri fault based on offset of the lower slope break of the Cross-Hosgri...
Authors
Jared W. Kluesner, Samuel Y. Johnson, Stuart P. Nishenko, Elisa Medri, Alex Simms, Gary Greene, Harrison J. Gray, Shannon A. Mahan, Jason Scott Padgett, Emma Taylor Krolczyk, Daniel S. Brothers, James E. Conrad
Geologic Stories in Grand Canyon Geologic Stories in Grand Canyon
Take a trip through Grand Canyon with USGS geologists to learn about geologic mapping in this iconic landscape. On the trip, scientists from Arizona, New Mexico, California and Colorado also conducted a series of related research studies to inform the geologic maps and geologic history of Grand Canyon.
By
Core Science Systems Mission Area, Water Resources Mission Area, Environmental Health Program, National Cooperative Geologic Mapping Program, National Water Quality Program, Toxic Substances Hydrology, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, New Mexico Water Science Center, Southwest Biological Science Center, Denver Radiogenic Isotope Lab, Mineralogy and Microscopy Laboratory, New Mexico Water Science Center Sediment Laboratory, Organic Geochemistry Laboratory, Geological Materials Repository, Geology and Ecology of National Parks, National Hydrography, Science Data Management, Colorado River Basin: Actionable and Strategic Integrated Science and Technology
Science and Products
Earthquake Geology and Paleoseismology Overview
The goals of USGS earthquake geology and paleoseismology research are 1) to make primary observations and develop ideas to improve our understanding of the geologic expression of active faulting, and 2) to acquire data that will improve the National Seismic Hazard Model. Geological research allows us to characterize faults, including the identification of secondary seismogenic structures, to study...
Quaternary Hydroclimate Records of Spring Ecosystems
Desert springs and wetlands are among the most biologically productive, diverse, and fragile ecosystems on Earth. They are home to thousands of rare, endemic, and endangered plants and animals and reflect the availability and health of emergent groundwater. Despite the ecological importance of these wetlands, our knowledge of how they might respond to future environmental conditions is limited...
Western Basin & Range - Eastern California Shear Zone
The Eastern California Shear Zone (ECSZ) Mapping project, funded by the National Cooperative Geologic Mapping Program, combines surficial and bedrock geologic mapping, geophysical surveys, and high-resolution topographic data analysis with neotectonic, geomorphic, structural, volcanic, and geochronologic studies to better understand the tectonic framework and landscape evolution of the ECSZ in the...
Filter Total Items: 14
Luminescence Data For Floodplain Carbon Storage: Soil Organic Carbon, Surface Age, and Vegetation in an Icy River Corridor Luminescence Data For Floodplain Carbon Storage: Soil Organic Carbon, Surface Age, and Vegetation in an Icy River Corridor
Rivers are some of the most dynamic features of the Arctic landscape, yet their role in the global carbon cycle is poorly understood. Researchers are still unraveling the intricacies of how river dynamics control organic carbon (OC) accumulation, transport, and degradation in riverine systems. The interplay between permafrost thermal state in river corridors, snow and ice-affected...
Data Release for Timing and Abandonment of the Chemehuevi Formation: a Conspicuous Pleistocene Sedimentary Deposit of the Lower Colorado River Data Release for Timing and Abandonment of the Chemehuevi Formation: a Conspicuous Pleistocene Sedimentary Deposit of the Lower Colorado River
This data release contains data for the associated publication: Timing and Abandonment of the Chemehuevi Formation: a Conspicuous Pleistocene Sedimentary Deposit of the Lower Colorado River
Data Release for Luminescence: Neotectonic Mapping of Puerto Rico Data Release for Luminescence: Neotectonic Mapping of Puerto Rico
This report details the luminescence ages and characteristics of four (4) samples that were collected by Jessica Jobe and Rich Briggs of the USGS. These samples are from Holocene and Pleistocene sediments offset by a fault that is exposed in a road cut. The roadcut is in Puerto Rico at 18.003828 and -67.140249 with an elevation of 13.5 m. The sample depths from the modern surface varied...
Datasets documenting neotectonic mapping of Puerto Rico Datasets documenting neotectonic mapping of Puerto Rico
This data release documents neotectonic mapping of fault-related features on high-resolution lidar-derived topography, data documenting an exposure of the South Lajas fault, and summary information for active and potentially active Quaternary faults on the island of Puerto Rico. The data documenting the exposure of the South Lajas fault include detailed unit descriptions, radiocarbon...
Data release for Independent age estimates resolve the controversy of ancient human footprints at White Sands Data release for Independent age estimates resolve the controversy of ancient human footprints at White Sands
Human footprints at White Sands National Park, New Mexico, USA, reportedly date to between ~23,000 and 21,000 years ago according to radiocarbon dating of seeds from the aquatic plant Ruppia cirrhosa. These ages remain controversial because of potential old carbon reservoir effects that could compromise their accuracy. We present new calibrated 14C ages of terrestrial pollen collected...
Geochronologic and isotopic data for Paleohydrologic history of Pluvial Lake San Agustin, New Mexico Geochronologic and isotopic data for Paleohydrologic history of Pluvial Lake San Agustin, New Mexico
This dataset includes tables of radiocarbon, uranium thorium series, and luminescence geochronologic ages and stable carbon and oxygen isotope compositions for sedimentary and organic samples.
Filter Total Items: 28
Spatiotemporal variations in strain release and seismic rupture in multifault systems: An example from Panamint Valley, southeastern California Spatiotemporal variations in strain release and seismic rupture in multifault systems: An example from Panamint Valley, southeastern California
Geometrically complex, multifault ruptures have been observed in recent, damaging earthquakes in southeastern California, sparking renewed efforts to identify physical conditions that promote or inhibit fault discontinuity-spanning coseismic ruptures. The likelihood of ruptures propagating across fault discontinuities is thought to be partly controlled by fault geometries, rupture...
Authors
Aubrey LaPlante, Christine Regalla, Israporn Sethanant, Shannon A. Mahan, Harrison J. Gray
Evidence for nonlocal sediment transport on hillslopes from fault scarp morphology Evidence for nonlocal sediment transport on hillslopes from fault scarp morphology
Hillslope sediment transport processes such as bioturbation, rainsplash, and granular mechanics occur across the entire planet. Yet, it remains uncertain how these small-scale processes act together to shape landscapes. Longstanding hillslope diffusion theory posits that hillslope processes are spatially limited, whereas new concepts of nonlocal sediment transport argue otherwise...
Authors
Harrison J. Gray, Tyler Doane, Sylvia R. Nicovich, Christopher DuRoss, Ryan D. Gold
Timing and geometry of the Chemehuevi Formation reveal a late Pleistocene sediment pulse into the Lower Colorado River Timing and geometry of the Chemehuevi Formation reveal a late Pleistocene sediment pulse into the Lower Colorado River
The Chemehuevi Formation is a distinctive 50−150-m-thick wedge-shaped Pleistocene sedimentary unit deposited by the Colorado River. It lines the perimeters of the river’s floodplains and bedrock canyons for more than 600 km between the mouth of the Grand Canyon and the delta region in the Gulf of California. The formation is composed of a basal tan to light-yellowish-brown and pale...
Authors
Harrison J. Gray, Kyle House, Adam M. Hudson, Jorge A. Vazquez, Ryan S. Crow, Miriam Primus, Shannon A. Mahan, Tammy M. Rittenour, Keith A. Howard
Neotectonic mapping of Puerto Rico Neotectonic mapping of Puerto Rico
Puerto Rico is part of the Puerto Rico-Virgin Islands microplate, along the Caribbean–North American plate boundary between the Puerto Rico trench subduction zone and the Muertos Trough incipient subduction zone. Despite recent seismicity and geodetically constrained deformation of ~3 mm/yr of left-lateral shear across the island, Quaternary fault locations remain largely uncertain...
Authors
Jessica Ann Thompson Jobe, Richard W. Briggs, K. Stephen Hughes, J. Joyce, Ryan D. Gold, Shannon A. Mahan, Harrison J. Gray, Laura E. Strickland
The geochronology of White Sands Locality 2 is resolved The geochronology of White Sands Locality 2 is resolved
Rhode et al. (2024) allege that there are many “unresolved issues” with the geochronology of White Sands National Park (WHSA) Locality 2. They suggest there are substantial age offsets due to hard-water effects in the aquatic plants that were dated and that radiocarbon ages of pollen may be anomalously old due to reworking. In their view, the luminescence ages are likely to be maximum...
Authors
Jeffrey S. Pigati, Kathleen B. Springer, Harrison J. Gray, Matthew R. Bennett, David Bustos
High-resolution geophysical and geochronological analysis of a relict shoreface deposit offshore central California: Implications for slip rate along the Hosgri fault High-resolution geophysical and geochronological analysis of a relict shoreface deposit offshore central California: Implications for slip rate along the Hosgri fault
The Cross-Hosgri slope is a bathymetric lineament that crosses the main strand of the Hosgri fault offshore Point Estero, central California. Recently collected chirp seismic reflection profiles and sediment cores provide the basis for a reassessment of Cross-Hosgri slope origin and the lateral slip rate of the Hosgri fault based on offset of the lower slope break of the Cross-Hosgri...
Authors
Jared W. Kluesner, Samuel Y. Johnson, Stuart P. Nishenko, Elisa Medri, Alex Simms, Gary Greene, Harrison J. Gray, Shannon A. Mahan, Jason Scott Padgett, Emma Taylor Krolczyk, Daniel S. Brothers, James E. Conrad
Geologic Stories in Grand Canyon Geologic Stories in Grand Canyon
Take a trip through Grand Canyon with USGS geologists to learn about geologic mapping in this iconic landscape. On the trip, scientists from Arizona, New Mexico, California and Colorado also conducted a series of related research studies to inform the geologic maps and geologic history of Grand Canyon.
By
Core Science Systems Mission Area, Water Resources Mission Area, Environmental Health Program, National Cooperative Geologic Mapping Program, National Water Quality Program, Toxic Substances Hydrology, Geology, Geophysics, and Geochemistry Science Center, Geology, Minerals, Energy, and Geophysics Science Center, Geosciences and Environmental Change Science Center, New Mexico Water Science Center, Southwest Biological Science Center, Denver Radiogenic Isotope Lab, Mineralogy and Microscopy Laboratory, New Mexico Water Science Center Sediment Laboratory, Organic Geochemistry Laboratory, Geological Materials Repository, Geology and Ecology of National Parks, National Hydrography, Science Data Management, Colorado River Basin: Actionable and Strategic Integrated Science and Technology