What Does Old Faithful Look Like Below the Surface and Why is it There? New Hydrogeophysical and Time-Lapse Imaging of Old Faithful, Yellowstone National Park
Abstract
Typically within Yellowstone National Park, both fountain and pool geysers are observed to be very dynamic on time scales of minutes to hours as well as specific geysering characteristics (e.g. thrown water height, volume of water discharged, etc.). Questions remain about why geysers in close proximity behave differently let alone exhibit varying eruptive time scales (e.g. Old Faithful versus Spouter Geyser).
To address these questions and continue previous University of Wyoming studies of the in situ dynamic nature of geysers, we recently acquired surface hydrogeophysical and time-lapse geophysical imaging at Old Faithful in Upper Geyser Basin of Yellowstone National Park. These data in combination with earlier studies at nearby Spouter Geyser and Airborne Electromagnetic data collected in 2016 allow comparisons of "fountain" and "pool" geyser dynamics to an unprecedented scale. In this study at Old Faithful, both instantaneous measurements of 2D Surface Seismic Refraction, 2D DC Resistivity and Total Field Magnetics combined with repeated surface Transient Electromagnetics (TEM) and surface Nuclear Magnetic resonance (NMR) were collected. Time-Lapse measurements were acquired on either 6-10 minute (TEM & NMR) for 4-24 hours continuously. The aim is to observe multiple eruption cycles and gain better insight into the "bubble trap" model proposed for geysers in this area. Our data highlight the movement of water and gas through the "pipe" system under Old Faithful within the cemented glacial till and the underlying rhyolite as observed by changing electrical resistivity and water content/porosity. DC resistivity data image the "pipe" structure as gas inputs change distinct resistivity values at certain depths. NMR data illustrate that total water content varies no more than 2% between eruption and recharging. This indicates that very little of the total amount of water available to the system is loss during an eruption. Additionally, both geysers appear at the flanks of bedrock magnetic highs that are interpreted to be reflecting the rhyolite "bedrock" condition (e.g. topographically higher, less fractured, higher permeability, etc.).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V24B..02C
- Keywords:
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- 4302 Geological;
- NATURAL HAZARDS;
- 7280 Volcano seismology;
- SEISMOLOGY;
- 8424 Hydrothermal systems;
- VOLCANOLOGY;
- 8488 Volcanic hazards and risks;
- VOLCANOLOGY