magmadruk

Magmadruk is a term used in volcanology to describe the internal pressure of magma within a magma chamber and the pressure perturbations that can drive rock fracturing and volcanic activity. It refers to the overpressure that develops as magma accumulates, crystallizes, and releases gases, creating stresses in the surrounding rock.

The word is formed from elements meaning magma and pressure, and is used mainly in Scandinavian geological literature. It describes a physical state rather than a single observable phenomenon, and is often discussed in the context of how increasing chamber pressure can influence fracture networks, magma ascent, and eruption style.

Mechanisms contributing to magmadruk include magma recharge from deeper sources, exsolution of volatiles as pressure changes, crystallization and associated changes in volume, and gas accumulation within vesicles. As overpressure grows, surrounding rocks may crack, conduits can widen, and magma can commence ascent toward the surface. The balance between confining rock strength, chamber geometry, and the rate of pressure increase helps determine whether an eruption is effusive, explosive, or a mix of both.

In monitoring terms, magmadruk is inferred from geophysical and geochemical signals such as ground deformation, seismic tremor, and changes in gas emissions, rather than measured directly. Petrological indicators in erupted rocks, like vesicle textures and exsolution states, can provide corroborating evidence about past overpressure conditions.

See also: magma chamber pressure, volcanic unrest, overpressure, vesiculation.