Scientists from Virginia Tech and US Geological Survey used an 80-foot-diameter electromagnet to study the subsurface of Yellowstone National Park and learn more about the water system, a Press release said.
Yellowstone National Park is a geological feature that hardly needs an introduction. Millions of visitors come to this site every year to see bubbling mud cauldrons, crystal clear waters and the brilliant colors of the grand prismatic spring. The towering water eruptions at the Old Faithful are also a huge attraction but also add intrigue to the visit when you wonder where the water comes from?
Investigate the basement
“Our knowledge of Yellowstone has long had a gap underground,” explained Steven Holbrook, professor of geosciences at Virginia Tech. “It’s like a ‘mystery sandwich’ – we know a lot about surface features from direct observation and a fair amount about the magmatic and tectonic system many miles from geophysical work, but we don’t really know what that’s in the middle.”
To find out, the team used a unique instrument called SkyTEM which is a large loop of wire towed under a helicopter. The diameter of the loop was 80 feet and by sending electricity through it, the researchers created electromagnetic pulses that were sent underground and received responses from electrically conductive bodies.
Since a helicopter can travel at speeds of 40 to 50 mph, researchers were able to quickly survey large stretches of the 3,500 mile national park. The data they collected consists of more than 2,500 miles of helicopter lines that not only look beneath the park’s hydrothermal features, but also how these features are connected over great distances.
“Plumbing” in Yellowstone
Data captured by the team of scientists shows that the park’s hot springs are the result of the site’s geology. Faults and fractures in the subsoil contribute to the way hydrothermal waters rise more than half a mile below ground in nearly vertical ascents.
Beneath the volcanic flows in the park are shallower underground aquifers that are controlled by lava boundaries but mix with warm water that rises from the depths as it soars skyward.
The new research also sheds light on different chemistries and temperatures that have been observed at different sites in the park. Previously thought to be the result of unknown deep processes, subsurface data from the site has shown that the differences are only the result of variations in shallow groundwater mixing. Interestingly, the data shows that hydrothermal systems in the park up to 10 km apart are also related to each other.
The data has also sparked the interest of other scientific disciplines such as biologists and hydrologists who have already studied the site extensively. The results of the data were published in the journal Nature.
Summary: The nature of Yellowstone National Park’s plumbing system linking deep thermal fluids to its legendary thermal characteristics is virtually unknown. The dominant concepts of Yellowstone hydrology and chemistry are that fluids reside in reservoirs of unknown geometries, flow laterally from distal sources, and emerge at the edges of lava flows.1,2,3,4. Here we present a high-resolution synoptic view of the pathways of the Yellowstone hydrothermal system derived from electrical resistivity and magnetic susceptibility models of airborne geophysical data.5,6. Groundwater and thermal fluids containing appreciable numbers of total dissolved solids significantly reduce the resistivities of porous volcanic rocks and are differentiated by their resistivity signaturesseven. Clayey sequences mapped in thermal zones8,9 and boreholesten typically form at depths less than 1,000 meters on thermal fluid and/or gas conduits controlled by default11,12,13,14. We show that most of the thermal features are located above the high-flux conduits along buried faults lined with low resistivity, low susceptibility clay. Shallow sub-horizontal pathways feed groundwater into basins which mix with thermal fluids from vertical conduits. These mixed fluids emerge at the surface, controlled by surface permeability, and flow outward along deeper breccia layers. These flows, continuing between geyser basins, mix with local groundwater and thermal fluids to produce the observed geochemical signatures. Our high-fidelity images inform geochemical and subsurface models of hydrothermal systems around the world.