A gravimeter taking measurements in Long Valley, California

By California Volcano Observatory June 2026 (approx.)

Box-shaped electronic instrument with a digital screen set up on rocky terrain surrounded by dry vegetation and mountains in the background.

Detailed Description

Gravimeters, or "gravity meters", measure the strength of the Earth's gravitational field at any given point. This value may be affected by ground elevation, the density of the rock or material on which the gravimeter sits, and the presence of magma or fluids beneath the Earth's surface. USGS photo by J. Crozier.

Sources/Usage

Public Domain.