High Lava Plains (HLP) of Eastern Oregon
Known for its regionally extensive magmatism, Richard Carlson, David James and collaborators are working to determine the crustal and upper mantle structure beneath the High Lava Plains (HLP) of eastern Oregon and compare it with the geologic record in the area in order to understand the driving forces for the extensive magmatism and tectonic activity.
Starting in 2005 and extending into 2010, the HLP project, funded by the Continental Dynamics Program of the National Science Foundation's Earth Sciences Division, seeks to establish a better understanding of why the Pacific Northwest, specifically eastern Oregon's High Lava Plains, is so volcanically active. This region, chosen for study because of its high volcanic flux (this is the most volcanically active area of the continental United States), and its relatively young age, provides the team with an interesting and challenging problem. None of the accepted paradigms explain why the magmatic and tectonic activity extend so far east of the North American plate margin. By applying numerous techniques ranging from geochemistry and petrology to active and passive seismic imaging to geodynamic modeling, the researchers will examine an assemblage of new data that will provide key information about the roles of lithosphere structure, tectonics, flat-slab subduction, slab roll-back, and plumes as instigators of aerially extensive magmatism continuing from plate margins into the interior of the continent.
What do we aim to determine?
- Is a plume necessary for large-volume intraplate volcanism?
- Can shallow-dip subduction establish the conditions that lead to active tectonism and magmatism when the subducting plate eventually steepens?
- Does flow of mantle around the edges of a subducting plate instigate focused volcanism in the overlying crust?
- What role does "bottom topography" of the lithosphere play in localizing tectonomagmatism in the overlying crust?
- Is crustal extension the cause or expression of continental magmatism
To answer these questions, the multi-disciplinary research team installed a dense array of broadband seismometers across two transects of the HLP. The structural information returned from the geophysical components will be combined with the geologic history derived from volcanology-geochemistry-geochronology-petrology data and compared with geodynamic modeling of mantle flow expected for various models of slab and plume behavior in the "dying" continental convergent margin exemplified by the Pacific Northwest. The collaborative nature of this project will allow numerous students to participate in a diverse set of approaches (e.g. geophysical, geochemical, petrologic) to investigate solid earth processes including field data acquisition, data processing, and data analysis. This experience commonly creates increased interest and motivation in students that lasts throughout their careers.
This project, particularly in its study of recent volcanic centers such as Newberry Volcano and the Jordan Valley Volcanic Field, can assist in better definition of the volcanic hazard represented by the ongoing magmatic activity in eastern Oregon.