RUI: Reconstructing ancient terrestrial landscapes of the southeastern Columbia Basin

Whitman College, Walla Walla WA

Investigators

Abstract

Landscapes change over geological time as water, wind, and volcanic activity reshape Earth’s surface. In southeastern Washington State, today’s landscape reflects two events of unimaginable size: mammoth eruptions of molten lava and much later, Ice Age mega-floods that scoured and reshaped the landscape. This project focuses on the missing interval between these two events and uses ancient soils to learn about the environment when these ancient landscapes formed. Twelve undergraduate students will be engaged in research experiences that will incorporate field and laboratory techniques that are in wide use in the geosciences. The goal of this research is to characterize terrestrial environments following the eruption of the Columbia River Basalts in southeastern Washington and northeastern Oregon, and to reconstruct the geological processes that shaped the landscape in this area. This will be accomplished by creating a network of field sites across the southeastern Columbia Basin that expose weathered basalt contacts and paleosols. At each site the morphology of the contact and underlying basalt will be characterized, and samples will be collected for lab analyses of micromorphological features and bulk chemical abundances. Lava flows are exposed throughout the region at different elevations, allowing for the study of precipitation gradients and their influence on basalt weathering, and to measure differences in pedogenesis caused by exposure time or thermal diagenesis. These analyses will provide the ability to (i) better understand the timing of Cascade uplift and the subsequent aridification of the Columbia Basin, (ii) reconstruct the landforms caused by periods of glacial outburst flooding that predate the most recent Ice Age floods and (iii) distinguish original soil weathering from post-burial processes. This research will increase understanding of the complex tectonics of the Pacific Northwest and provide insights into the impact of megafloods in shaping the terrestrial landscape. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.