DETERMINATION OF INFLATION BASED ON ANALYSIS OF FLOW STRUCTURES NORTH OF MITER CRATER, ICE SPRINGS VOLCANIC FIELD, BLACK ROCK DESERT, UTAH

Black Rock Desert volcanism is the result of the E-W crustal extension which created the Basin and Range Province of the United States. The most recent volcanic activity in the Black Rock Desert occurred in Ice Springs Volcanic Field approximately 600 ya. This study focuses on the analysis of structures in an area of low depression north of Miter Crater, in Ice Springs Volcanic Field. The surface of the depression features columnar jointing indicating that it was emplaced as a pahoehoe flow.

Three major types of structures were observed: flow walls, islands of lava with flat tops referred to as lava pillars, and tumuli. The flow walls bound the depression to the north and east. Cross sections of the tops of bounding flow walls, pillars, and tumuli were mapped using a cm scale DGPS unit. Tumuli occurred near and along the bounding walls. Lava pillars occurred throughout the center of the depression. Tumuli featured columnar jointing and were linked to each other and the pillars by a network of fractures. The walls and pillars had an irregular spatter coating. The spatter featured elongated vesicles, columnar jointing, and vertical striations. Structural measurents were taken for columnar joints, striae, pillars, and walls. The Stratigraphy was documented for the walls and three pillars.

The stratigraphy correlated across the pillars and the walls. The topmost layer observed ranged in thickness from 0.2m – 0.4m, and was the least vesiculated layer. The mode of vesicle size in this layer was less than 0.5 cm. This layer had a cavity separating it from subsequent layers in both of the walls and all of the pillars. The underlying layers were red and highly vesicular with black boundaries. The N. wall, E. wall, and one of the pillars featured vesicle casts: vesicles at the boundary of a flow layer that were later infilled with lava. Thicknesses of stratigraphic layers showed variation both within structures and between them.