Yellowstone Volcano's Vast, Unknown Underground Plumbing System Uncovered

Scientists have revealed the huge underground plumbing system of Yellowstone volcano in unprecedented detail. The findings, which are the result of a mammoth subsurface mapping task, could help answer multiple unanswered questions about hydrothermal activity at the supervolcano.

Yellowstone sits above an enormous hotspot—an area of Earth's crust where hot plumes rise from the mantle below, resulting in volcanic activity at the surface. The first caldera-forming eruption at Yellowstone took place about 2.1 million years ago and since then there have been two other huge eruptions—one around 1.3 million years ago, and another around 630,000 years ago.

The region is known for its hydrothermal activity, with over 500 geysers. This is the largest concentration of active geysers on Earth, accounting for half of all known examples.

Geologists have a fairly good understanding of the volcanic system beneath the surface of Yellowstone. The volcano has one smaller chamber that sits in Earth's crust, while another, much larger reservoir sits in the lower crust, feeding the upper chamber.

However, what sits between the magma chamber and the surface is something of a mystery.

Researchers led by Carol Finn, from the U.S. Geological Survey, Denver, spent weeks flying a helicopter over Yellowstone to develop a view of the plumbing system that controls and facilitates hydrothermal activity.

 Chromatic pool at Yellowstone National Park
The Chromatic pool at Yellowstone National Park. Scientists have mapped the plumbing system beneath Yellowstone. Getty Images

They flew a helicopter with an 80-foot-wide electromagnetic hoop dangling beneath it. Water is much better at conducting electricity than rock, so the hoop was able to detect variations between wet and dry rock. The helicopter was flown back and forth across the park to measure electrical conductivity and magnetic properties, creating a picture of the plumbing system. The findings were published in the journal Nature.

"This is the first survey of its kind over a large, active hydrothermal system, so we were ecstatic when we saw the first images over Old Faithful that showed that our experiment had worked—that [we] could see the fluids and clays that have long been inferred," Finn told Newsweek.

"We were surprised at how extensive the plumbing system is, how clearly we could image it and differentiate the signals from cold and hot fluids, and that there are gaps in the plumbing system in the middle of Yellowstone. In addition, we were surprised that we were able to locate many clay regions and that these mark the tops of the vertical channels for hot fluids."

The results showed hot hydrothermal fluids rise almost vertically from depths of about 3,000 feet before arriving at the major hydrothermal fields. These fluids mix with groundwater from within and beneath lava flows.

"The water from Yellowstone's high precipitation is able to penetrate to about three miles deep along the many faults in the region," Finn said. "This water is heated up by the deep magma and returns to the surface along faults to the surface, as well as spreading horizontally along gaps between the stacks of lava flows that cover the park. This unique setting produces the fantastic, dynamic hydrothermal features at the surface."

In total, the experiment generated over 2,500 miles of helicopter lines. In a statement, study co-author Steven Holbrook, from Virginia Tech, said the data set is so huge "we've only scratched the surface."

The data gained will help scientists answer many unknowns about the geology and hydrology of Yellowstone, as well as the microbiology within the hydrothermal systems. This could provide an insight into water and lava flows, to estimate eruptive volumes and to better understand hydrothermal explosions, which are a hazard in the park.

"In the future, the integration of our models with new, deeper-sensing electromagnetic data offers the possibility of imaging the connections between Yellowstone's shallow and deep hydrothermal systems and magma," Finn said.