GEOC/GEOL/GEOP/HYDR592 Spring 2012 Presentations

(4:00 PM Wednesday in MSEC101)

Apr. 25 Oral presentation # 1

Characterization of geyser eruptions using infrasoud

Aida Quezada Reyes

Advisor: Jeffrey Johnson

Introducer: Rebecca Morris (rebecca@nmt.edu)

Geysers are springs with intermittent activity consisting of the sudden ejection of hot water and steam. As with volcanoes, infrasonic airwaves produced by different geysers provide information about the processes that occur near the nozzle, as well as the amount of flux released during each eruptive episode. The aim of this study was to investigate the types of sources related to the activity observed at Sawmill and Great Fountain Geysers, Yellowstone National Park, Wyoming. The acoustic signal was measured by arrays of microphones deployed around Great Fountain Geyser between August 9th to 13th, 2011, and during one hour on August 16th, 2011 at Sawmill Geyser. Infrasound was analyzed to determine the pressure field generated during an explosive phase. We propose that the sound recorded at Sawmill is a combination of: 1) a steam-filled bubble oscillating, as it contracts once the water inertia forces it to overshoot its equilibrium radius, and 2) its subsequent bursting that results in a violent steam and water discharge. Both phenomena radiate pressure pulses. We also observed volumes of water and steam ejected from Great Fountain during pulses of an eruptive episode ranging between 0.1 and 0.5 m3. In both geysers, results show a good correlation with video sequences of the eruptions. A better understanding of the discharge cycles of geysers, using infrasound, may play a significant role in volcano monitoring due to their remarkable similarities with volcanoes regarding eruption dynamics, and flux recharge processes.

Apr. 25 Oral presentation # 2

The clastic injectites in the dry Cimarron Valley area of Union County, New Mexico, and their effects on caprock integrity

Yong Jae Oh

Advisor: Peter Mozley

Introducer: Drea Killingsworth (dkilling@nmt.edu)

Although numerous clastic plugs are well exposed in the Dry Cimarron Valley, Northeastern Union County, New Mexico, no one has so far studied the effects of clastic injectites on caprock integrity in relation to porosity and permeability. Both porosity and permeability are critical factors to both petroleum industry and CCS (Carbon Capture and Sequestration) projects. Those people interested in the outcrops have mainly focused on ore deposits, stratigraphic classifications, and/or their origins which have remained unclear with different views. With the outstanding outcrop found in roadcut, however, it gives rise to better approach to plugs with internal geometries of the well-exposed cross-section and provides opportunities to have more agreeable hypotheses on formation of plugs and dike in this area. Also, other types of clastic plugs with fairly mineralized or highly fluidized features have been examined through petrographic analyses, comparing them to both the plug in roadcut and surrounding stratigraphic units which in turn may give clues for their characteristics on fluid properties. The injectites consist mainly of sandstone (arkose to subarkose), mudstone, and carbonate rocks whereas the host units (Trsc & Trt) are dominant of mudstone and carbonate rocks. Unlike the other injectites in sandstone or carbonate rocks, the plug in roadcut exhibits varied lithological and spatial compositions from mudstone with/without sandstone of the inside to sandstone of the outer rim with a wide range of low to high porosity and permeability. The plugs and dikes including the one (except for sandstone in transition zone) in roadcut mostly resulted in low porosity (<4.3%) and permeability (<8.1mD) due to cementation. Even though the host unit has favorable results with less porosity (<3.7%) and permeability (<3mD), the injectites may be considered not to bleach and damage the caprock integrity. The transition zone of the plug in roadcut, however, with higher porosity (13%) and permeability (<98mD) may possibly provide seal bypass systems, compromising an effective seal for petroleum or CO2.