Tag: Geological Science

Using Forward Modeling to Optimize the Geometry of Geophysical Networks at the Summit of Kilauea Volcano: A Matter of Great Gravity

Presenter: Patricia Macqueen, Geological Sciences

Poster: B-8

Mentor: Katherine V. Cashman, Geological Sciences

Minute changes in the gravitational field of a volcano can give early warning of subsurface magma accumulation or withdrawal long before other more traditional precursors (e.g., seismic and deformation) and provide a valuable data set that is complementary to other data sets. Scientists have been monitoring gravity changes at the summit of Kilauea Volcano, Hawaii for decades, and these data sets have yielded valuable insight into volcanic activity at Kilauea. However, we currently have a poor understanding of the bias imposed by network geometry. My work focuses on using forward models of three known magma storage areas beneath Kilauea’s summit to test the resolving power of the current network. This forward modeling indicates that the current network can distinguish changes from sources near Halema`uma`u Crater and Keanakakoi Crater very well, but that additional station coverage is needed to decrease bias from network geometry in the south caldera region — known to be the primary magma storage reservoir beneath the summit. To this end I have suggested 5 new station sites in the south caldera area and evaluated the improvement that these stations would bring to the network. Forward modeling has also clarified the ability of the network to resolve sources with different mass changes and depths, and given insight on which stations are most useful for monitoring known sources of subsurface magma storage.

Lichenometric Dating Using Placopsis lambii Applied to the Yachats Basalt, Central Oregon Coast

Presenter: Logan Wetherell

Mentor: Josh Roering

Oral Presentation

Major: Geological Science

Surface exposure dates estimated through lichenometric growth rates can be used to document geologic events where other methods of dating rock surface exposure are not applicable. Largest lichen diameter measurements of pioneer species Placopsis lambii were taken at 10 sites with independent ages along the Yachats Basalt in the central Oregon coast to construct a regional growth curve to be used in estimating surface exposure dates. Largest lichen diameters were recorded across 25m2 swaths of non-calcareous rock at each site and recorded to establish two growth phases of P. lambii. Lichen colonization occurs approximately 5 years after surface exposure and lichen diameter increases at 1.2mm/yr to 1.5mm/yr for approximately 20 years. After 20 years, we observed slow linear growth of <0.2mm/yr as biological competition or spatial constraints from nearby P. lambii colonies impeded growth. We expect that P. lambii could be applied as a lichenometric dating species for exposed surfaces where the timescale of rockfall are less than 100 years and can provide useful information of regional rockfall rates.

Post-Burn Geomorphic Changes in the Oregon Coast Range

Presenter(s): Evelyn Meador − Geologic Sciences

Faculty Mentor(s): Joshua Roering

Poster 5

Research Area: Geological Science

Funding: Presidential Undergraduate Research Scholars

Wildfires are prevalent in the Oregon coast range, but studies on the post-fire geomorphic changes and hazards are limited in the region. Processes like dry ravel movement, hydrophobicity, and tree root strength decreases are present and contribute to land and mudslides, but the extent of which is not known. By repeatedly visiting the Horse Prairie Fire in the Oregon coast Range and observing and documenting changes and sediment movement, we gained insight into the processes that shape post-burn sites. Water, particularly in the form of precipitation, shapes the land after a burn. The rain in the coast range is seasonal, and the site typically experiences monthly storms of one to two inches. These storms move great amounts of post- fire debris and can cause landslides. The goal of this study is to see if there is a correlation between slope angle and sediment transport, which would greatly help organizations like the United States Geological Survey create accurate hazard maps for the Pacific Northwest.