A group of US Geological Survey (USGS) geologists have discovered signs of rhyolitic volcanism in the northeast-shifting Yellowstone caldera. The Yellowstone Caldera, a volcanic caldera and supervolcano located in Yellowstone National Park in the western United States, is often referred to as the Yellowstone Supervolcano due to its colossal size; it's one of the largest on Earth.
The new research, in collaboration with colleagues from Oregon State University and the University of Wisconsin-Madison, details how they utilised an electromagnetic geophysical method to investigate the ground beneath the Yellowstone caldera. The team adopted a unique approach: carrying out a comprehensive magnetotelluric survey of the entire caldera. This method involved measuring electromagnetic geophysical properties that account for variations in Earth's magnetic field, enabling deductions about the conductivity structure of the crust.
The study, published in the journal Nature, revealed that there are at least seven distinct magma regions beneath the caldera, some feeding others, located at depths ranging from 2.4 to 29 miles, near the mantle boundary.
The researchers found that the most active melt storage deposits were located in the northeastern parts of the caldera.
These deposits contained basaltic magma in their lower sections and rhyolitic magma in their upper sections.
The team managed to estimate the quantities, discovering a storage of melt material of approximately 388 to 489 cubic kilometers - a volume significantly larger than in the south, west, and north, where previous eruptions had been concentrated.
Past research has revealed that the supervolcano has undergone three major caldera-forming eruptions over the last 2.1 million years, with the most recent being a lava flow around 70,000 years ago. The timing of its next eruption remains a mystery.
Previous attempts to accurately determine the type and quantity of material beneath the Yellowstone caldera have also produced inconsistent results due to the extreme conditions.
