"How far beneath my feet is there magma?" This question, pondered by many in Yellowstone National Park, has driven scientists to delve deeper into the mysteries of the Earth's fiery heart.
In the summer of 2020, a team of seismologists, led by researchers from Rice University, used a 53,000-pound truck to create seismic signals, like tiny custom earthquakes, in Yellowstone National Park. The goal was to obtain a sharper view of the top of the magma reservoir.
Published in Nature in 2025, the results revealed a sharp transition marking the magma chamber top at about 3.8 kilometers (2.4 miles) depth beneath the northeastern part of the caldera near the Yellowstone River. The boundary is less than about 100 meters thick.
The team also discovered a three-part mixture of supercritical fluid bubbles, magma, and solid mineral crystals at the top of the reservoir. This discovery aligns with geochemical models indicating that bubbles emerge from magma at shallow depths.
While bubble accumulation can be a precursor to eruptions, the Yellowstone magma system appears stable, with about 14% fluid and 86% solid crystals in the cap layer. This configuration allows bubbles to rise efficiently, preventing pressure build-up.
These findings offer new perspectives on Yellowstone's magmatic system and demonstrate the potential to measure bubble accumulation beneath volcanoes globally. Yellowstone serves as a natural laboratory, enhancing our understanding of volcanoes and their eruptions worldwide.