Yellowstone National Park has long fascinated scientists, particularly due to its unique geological features, including iconic geysers, mud pots, and various hydrothermal wonders. For decades, researchers have diligently studied the park's magmatic system, but a breakthrough in understanding the conditions underground was recently achieved by a professor at the University of Utah.
The journey began in 2020 when Jamie Farrell, then a research associate professor of geology and geophysics and chief seismologist at the U.S. Geological Survey's Yellowstone Volcano Observatory, collaborated with researchers from the University of New Mexico. Their objective was to gain a deeper understanding of the volcanic system by using higher-resolution images to explore subsurface features.
Since the magmatic system lies beneath the surface, Farrell and his team employed a technique known as tomography, similar to the methods used in medical imaging, such as CT scans and MRIs. To facilitate this, they utilized an array of devices called seismometers, which capture artificial mechanical vibrations that replicate seismic waves from natural events. “We deployed approximately 650 temporary seismometers throughout the Yellowstone area, primarily along the roadways,” Farrell explained.
To create the necessary seismic waves, the team introduced a vibroseis truck, a device typically used in oil and gas exploration. The truck vibrated the ground at 110 locations, delivering 20 treatments, each lasting 40 seconds. “In a sense, we're causing our own earthquakes, and we record all that data on the seismometers,” said Farrell. The extensive deployment of seismometers allowed the team to achieve a higher resolution image of the subsurface layers.
Through the analysis of artificial seismic waves, the researchers discovered that the top of the magma chamber lies approximately 3.8 kilometers (about 12,500 feet) beneath the Earth's surface, sharply separated from the overlying rock strata. Their findings, published in the journal Nature, also revealed that the uppermost portion of the magma chamber is composed of roughly a 50/50 mixture of volatile gases and liquids. “This indicates that the Yellowstone magmatic system is effectively degassing, which is a positive sign,” Farrell noted. The release of gas from the solution towards the surface reduces the risk of pressure buildup, which could lead to explosive eruptions.
Farrell reassured the public regarding the long-dormant Yellowstone volcano, stating that it is currently not at risk of an imminent eruption. “We are observing only about 7% to 15% molten material in this magmatic system, while typically, a minimum of 50% molten material is required for magma to become mobile and erupt,” he explained. Thus, it appears that the system is not close to being ready for an eruption.
Mike Poland, the scientist in charge of the Yellowstone Volcano Observatory, highlighted that this research offers crucial insights into the structure of Yellowstone's magma body. Understanding this structure helps scientists learn more about the heat engine powering Yellowstone and how melt is distributed throughout the region. “This knowledge can influence how we assess volcanic hazards,” Poland added.
Yellowstone serves as a unique "laboratory volcano," allowing researchers to apply their findings to better understand other, more active volcanoes worldwide. Notable examples include Campi Flegrei in Italy and Santorini in Greece, which presents its own set of challenges due to its mostly underwater nature.
Farrell expressed optimism about the potential of this study to advance the collection of high-resolution images of magmatic systems, particularly in understanding the interactions between Yellowstone's magmatic system and the surrounding hydrothermal features. “I believe we can utilize this approach to gain a clearer perspective on why these large, high-thermal basins are located where they are,” he concluded.
