Structural Analysis of Tensile Fracture Sets in The Medicine Lake Dacite Lava, California

Kailee Gokey* and Graham D.M. Andrews, Department of Geology & Geography, West Virginia University, Morgantown, WV 26506

Field (Broad Category): Geography/Geology (Agricultural & Environmental Sciences) 

Student’s Major: Geology 

The Medicine Lake Glass lava, Medicine Lake volcano, in Siskiyou County, California is a dacitic lava flow covering an approximate area of 2.4 square kilometers. Previous studies of this dacite flow have documented the orientations of small numbers of fractures in the Medicine Lake dacite, but these studies did not integrate their formation with the emplacement of the lava. We present a preliminary structural analysis of tensile fracture sets in the upper surface of the Medicine Lake dacite lava. Using Google Earth Pro and orthorectified drone images, we have analyzed 1,171 tensile fractures across the entire lava to produce a representative data-set. We have measured the lengths, widths and orientations of major fractures, and used drone image-derived 3-D models and Digital Elevation Models (DEMs) to estimate fracture depth and fracture surface curvature. On-going research into silicic lava flow emplacement emphasizes the importance of tensile fracturing during emplacement and the extreme unlikeliness that silicic lavas will fold. The unlikeliness of silicic lava folding contradicts the existing literature that interprets many upper surface structures as ductile and compressional (i.e. folds). Therefore, it is important to understand the structural context of undisputed fracture sets to assess how and when they formed. 

Funding: National Science Foundation 

Program/mechanism supporting research/creative efforts: WVU 497-level course