Explosive volcanic eruptions generate pressure disturbances in the atmosphere that propagate away either as acoustic or as shock waves, depending on the explosivity of the eruption, Both types of waves are recorded on microbarographs as 1- to 0.1-hertz N-shaped signals followed by a longer period coda. These waveforms can be; used to estimate burst pressures and gas concentrations in explosive volcanic eruptions and provide estimates of eruption magnitudes.