How Much Magma Is Under Yellowstone
Yellowstone sits above a hotspot where partially molten rock rises from deep in the mantle. The upper crust hosts a large zone of partially molten material that feeds the caldera and its geothermal features.
Size and Volume of the Magma Reservoir
Studies using seismic imaging estimate the total volume of partially molten material in the upper crust is roughly 2 to 3 percent of the volume of the underlying plume. The deeper mantle plume supplies heat and material, while the shallow reservoir stores melt that can move upward during eruptions.
Temperature, Composition, and Eruption Potential
Magma beneath Yellowstone is typically basaltic to rhyolitic in composition, with temperatures around 700 to 1,300 degrees Celsius. Most eruptions in the region are explosive silicic events, and monitoring shows ongoing uplift and deformation tied to magma movement. For current data, see the United States Geological Survey Yellowstone Volcano Observatory page at https://www.usgs.gov/volcanoes/yellowstone-volcano-observatory.
