Measuring the Gravity and Magnetic Anomaly of a Rising Lava Plume Chris Jaeger December 3, 2015

Methods (I) Magnetic Anomaly (generalized to 2D): - “is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks” (Wikipedia). F a / H a /Z a = magnetic fields induced in a geologic body by Earth’s field F A/T = component of F a in the direction of the undisturbed main field, F E/U, that affects the magnetometer reading i = inclination (angle the vector makes with horizontal plane) k = magnetic susceptibility Assumptions: Uniform density (ρ), magnetic susceptibility (k), plume is a sphere

Methods (II) Gravity Anomaly (Generalized to 2D) Gravity surveys are used to “detect variations in the densities of subsurface materials by measuring gravity at the surface and analyzing the differences in the recorded values” (Burger 349). G = gravitational constant R = radius of sphere Ρ = density X = horizontal position Z = depth to center of sphere g = gravity anomaly (mGal)