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The Pacific Northwest is an area created by active and complex geological processes. On its path to the Pacific Ocean, the Columbia River slices through a chain of active volcanoes located along the western margin of the U.S. in Washington, Oregon, and northern California. These volcanoes rest above the active Cascadia subduction zone, which is the boundary where the oceanic tectonic plate dives beneath the continental plate. Consequently, this area with urban centers and transportation networks is subject to earthquakes, volcanic activity, landslides, and floods. Geologic mapping and research supports resource assessments, the understanding of natural hazards, the delineation of ecosystems, and defines the framework geology of this unique region.
The primary focus of this project is geologic mapping. Most mapping is conducted at the 7.5' quadrangle scale but in many instances these maps are compiled into regional compilations such as the Portland basin map. The focus areas for mapping are strategically chosen based on the overall project objectives but also in consultation with other USGS researchers, universities, State and local agencies, and the private sector.
The term “Cascadia” encompasses the volcanoes of the Cascade Range and the subduction zone that feeds them. This area in the Pacific Northwest is a region of significant seismic hazards, and much is unknown about the potential size and magnitude of earthquake ruptures and the effects of earthquake shaking. This translates into major uncertainties in earthquake hazard assessments of the U.S. Pacific Northwest that can lead to ineffective preparedness measures.
The primary objectives of this task are to evaluate upper-plate deformation in the Cascadia forearc (i.e., the area between the Cascade Range and the oceanic subduction zone), determine its linkages to the active Cascadia subduction zone, and quantify the associated seismic, tsunami, and landslide hazards.
Columbia River Corridor Mapping
The lower Columbia River corridor hosts most of Oregon’s population and is an internationally vital transportation link connecting the interior United States with Trans-Pacific trading partners. The Columbia River is unique; it is by far the largest river in the world to bisect an active arc (i.e., volcanoes of the Cascade Range) which forms above a subduction zone. Vital infrastructure, including interstate highways, hydropower dams, rail lines, natural gas and petroleum pipelines, electrical-power transmission lines, and fiber-optic communications cables, are all routed through the Columbia River Gorge, where the river bisects the Cascade Range. In this narrow gorge, infrastructure is vulnerable to a variety of hazards: earthquakes, volcanoes, landslides, and floods. As urbanization expands into these areas, increasing conflicts arise with resource extraction (water, forestry, fisheries, aggregate resources, hydroelectric power), recreational activities, and natural hazards.
The primary objective of this task is to understand the Columbia River’s recent history and basin evolution by providing a synoptic geologic framework based on 7.5-minute scale mapping of this region.
Columbia Basin Landscape Evolution
The Columbia River and the tributaries that feed it have evolved dramatically over recent geologic time, beginning with the large Miocene flows of the Columbia River Basalt Group (CRBG) that filled a pre-existing topographic basin east of the Cascade Range. Deformed sedimentary strata of the Ringold, Palouse, and other formations blanket the basalt. River incision has carved through these units. Recent glaciations have left a legacy of temporary lakes, massive outburst floods, and deposits of glacial sediments and landforms.
The primary objective of this task is to understand the overall geologic evolution of structures (faults and folds) and landforms resulting from glacial retreat and floods from ice-dammed lakes the Columbia Basin, including the forces and events driving basin integration and river pattern development; the topographic, geologic, and ecologic effects of Quaternary ice sheets and associated megafloods; and the relations of these driving forces to regional hazards, resources, and ecosystems.
Evolution of the Cascade Range
The Cascade Range in Washington, Oregon, and northern California is comprised of dozens of iconic and active stratovolcanoes such as Mount St. Helens and Mount Hood, all forming above an active subduction zone. Yet the volcanoes are only one element of this continental scale mountain range which has had a 40-million-year history of crustal deformation, vertical uplift, volcanism, and erosion. The modern Cascade Range plays a critical role in regional climate and weather patterns, distribution of mineral and water resources, ecosystems, and the types and magnitudes of natural hazards.
This primary objective of this task is to understand the past and ongoing drivers for the growth and evolution of the Cascade Range and how these factors relate to resources, hazards, and ecosystems.
Columbia River Basalt Group Stratigraphy and Deformation
The Columbia River Basalt Group (CRBG) is the youngest large igneous flood basalt province on Earth and covers an area of ~160,000 km2, mostly in eastern Washington and Oregon, and western Idaho. Within this area, known as the Columbia Plateau or Columbia Basin, the CRBG is up to 2 km thick. Individual lava flows extend throughout this region and across the Willamette Valley and Coast Ranges to the west, where some flows reach the Pacific Ocean. The Grande Ronde Basalt (GRB), which makes up ~85% by volume of the CRBG, hosts the primary aquifer systems in the region, particularly in the arid Columbia Plateau province. This region is seismically active and includes numerous dams along the Columbia River as well as the Hanford nuclear production complex (mostly decommissioned) that houses large quantities of high-level radioactive waste.
The primary objective of this task is to use geochemical and paleomagnetic techniques to map the stratigraphy of the basalt flows of the CRBG and GRB. An improved map will support hydrogeological models and studies to assess the potential for carbon dioxide sequestration in porous volcanic rocks.
Below are other science projects associated with this project.
Below are data or web applications associated with this project.
Below are publications associated with this project.
We collaborate with a wide variety of cooperators in our work, from other Federal and State agencies to various institutions of higher learning, to assist in the collection and analysis of essential data.