Type: 
Senior Thesis Presentation
Date-Time: 
Tuesday, May 26, 2015 - 13:00 to 14:00
Location: 
279 Weniger Hall
Event Speaker: 
L Bonner
Local Contact: 
Janet Tate
Abstract: 

The Cascade Volcanic Arc has been the subject of extensive study in the past due to its high activity and proximity to metropolitan areas. The triangle formed by the volcanoes Mount St. Helens, Mount Rainier, and Mount Adams is of particular interest because of the potential danger and the geological complexity of the area. Trapped marine sediment and melt caused by volcanism are the two prevailing hypotheses that may explain the presence of anomalously high conductivity spread throughout the region. The magnetotelluric method was used to determine the shape and thus potential causes of the Southern Washington Cascades Conductor (SWCC) anomaly. Electric and magnetic field data were measured throughout the region, and a 2D cross-section was analyzed to determine the conductivity landscape of the area. Conductivity was determined indirectly through the computational process known as smoothness constrained inversion, which produced a model to fit the observed data. The best potential model was generated by extensively altering parameters and then checked with preexisting surveys. The model was found to strongly agree with both the marine sediment and volcanism causes of the conductive anomaly in different portions of the region. Geological complexity prevented a definitive conclusion from being drawn, though the results suggested that the cause of the SWCC related to the geological factors of the area. Marine sediment was determined to be the cause in regions with surface marine rock, while melt corresponded to locations near the three volcanoes. The results may aid in the iMUSH project that is currently surveying the entire region with multiple geophysical imaging methods to officially determine the cause of the conductivity and draw societal and economic implications of the area.