A type of volcanic activity marked by very explosive eruptions which occur after long periods of dormancy, during which gas pressures in the underlying magma have built up sufficiently to eject the plug of solid lava from the vent. Escaping gases, exsolved in the magma, produce a mobile, frothy lava (pumice) and clouds of ash and gases are released into the air. See volcano. Compare hawaiian eruption; peléean eruption; plinian eruption; strombolian eruption; surtseyan eruption; vulcanian eruption.