Julianna Martin

Major: Geology, Environmental Science

Faculty Advisor: Elizabeth Cassel

Project Title:

Recurrence intervals of glacial Lake Missoula flooding events

Abstract

From 21,000 to 14,000 years ago, a series of massive-scale floods impacted the landscape of the northwestern United States carving channels, eroding and depositing sediment. Glacial Lake Missoula was fed by an accumulation of glacial meltwater and the Clark Fork River that was dammed by the Purcell Lobe of the Cordilleran Ice Sheet. Periodic breaks and reformation of this ice dam caused intervals of lake drainage, with floodwaters traveling westward into the Columbia and Snake Rivers. The time intervals of these floods have only been loosely hypothesized and can be found using radiometric dating of carbon-14 in plant material along with sediment stratigraphic properties to determine the time between flooding events. Radiometric samples and stratigraphic data were taken from chosen field sites in the source waters and flood water drainage areas of the Missoula Floods, though all radiometric dating information is still being processed. By measuring stratigraphic sections in both Missoula lacustrine deposits and Pasco Basin flood deposits, flow properties dictate composition and give us insight into flood intervals. Correlating the stratigraphic records of flood source and sink locations and comparing them to paleoclimatic changes, we can establish a relationship between climate and flooding events. This holds implications for our contemporary climate shift and subsequent change in global ice.

Funding: Summer Undergraduate Research Fellowship (U of I Office of Undergraduate Research), Idaho State Board of Education