Multibeam echosounding as a tool for mapping geologic features, bathymetry and modern vents, Yellowstone National Park, Wyoming

Yellowstone National Park (YNP) is a unique area for study due to the broad range of geologic and geomorphic agents that have sculpted this terrain over time. This research employed a multibeam echosounder (MBES) in Lewis Lake and Yellowstone Lake, in August 2011, to describe and interpret the geologic and geomorphic processes that have shaped Lewis Lake, as well as enhance our understanding of selected hydrothermally-active areas within Yellowstone Lake. Since the eruption that formed the present day caldera 640,000 years ago, dozens of smaller eruptions of differing compositions have occurred. The first-ever bathymetric and acoustic backscatter map of Lewis Lake shows that the lake morphology has been shaped by at least four separate volcanic events. These include tuff, rhyolitic and pyroclastic flows that have altered the hydrothermal plumbing of the lake bed. Using this data, a timeline for the evolution of Lewis Lake has been constructed that allows the geology of the lake floor to be integrated into existing ‘onshore’ outcrop studies. MBES mapping was also used to examine three areas hydrothermally active areas of Yellowstone Lake: the Inflated Plain, Elliot’s Crater, and the Stephenson Island depression chain. These surveys yielded high-resolution bathymetric maps. Additionally, acoustic returns from the water column were used to determine the location of active degassing areas, as well as rates of gas discharge from a hydrothermal crater in the Inflated Plain, Yellowstone Lake. Using the acoustic returns in the water column, a rate of 0.72-726.6 g m-2 day-1 was calculated to be erupting from this individual sub-aqueous crater. These rates are consistent with gas discharge directly measured in other hydrothermal vents around the world. These results have shown the potential for MBES technology not only to produce high-resolution bathymetric maps, but also aid in geologic mapping as well as geohazard evaluation in subaqueous hydrothermal environments.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Geology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Cash, Ronald

Contributors dc:contributor

• Best, Jim

• Yellowstone National Park
• Hydrothermal
• bathymetry
• multibeam
• vent
• acoustic
• remote sensing

Statement dc:rights

• Copyright 2015 Ronald Cash

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/88224

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/88224