March 25, 2024 — Annual Kīlauea gravity survey

Gravity measurements detect subsurface mass change—for example, magma accumulation or removal beneath the surface. If magma is filling or draining void spaces, it may not be signaled by ground deformation or earthquake activity, but it will be signaled by gravity because of the mass change. In this way, gravity is a way of detecting changes in the magma reservoir that might otherwise be hidden. This photo shows scientists taking gravity measurements on the floor of Kīlauea caldera. Lava flows from Kīlauea summit eruptions in 2023 steam in the background, and the caldera walls rise above. The scientist is straddling the gravimeter (small silver box) to shield it from the wind. USGS photo by A. Ellis.