Knowra Explosive eruption Explosive eruption An explosive eruption fragments magma and ejects ash, gas, and rock under high pressure. It can produce towering columns, pyroclastic flows, and widespread tephra deposits.
Magma : Molten or partially molten rock beneath Earth’s surface, containing crystals and dissolved gases. Dissolved gases in magma supply the pressure that drives explosive fragmentation.
Volcanic ash : Fine fragments of volcanic rock, minerals, and volcanic glass smaller than two millimeters. Ash clouds can disrupt aviation, damage infrastructure, and harm health far from a volcano.
Mount St. Helens 1980 eruption : A major explosive eruption on May 18, 1980, that devastated part of Mount St. Helens in Washington State. Its lateral blast and subsequent column produced contrasting explosive hazards.
Effusive eruption : A volcanic eruption that releases lava relatively gently, without sustained explosive fragmentation. It contrasts with explosive eruptions, which eject fragmented magma under high pressure.
Pyroclastic flow : A fast, hot flow of volcanic gas, ash, and rock fragments moving down a volcano’s slopes. These currents can devastate areas close to an explosive eruption.
Volatile (geology) : A substance, such as water or carbon dioxide, that readily forms gas from magma as pressure falls. Exsolving volatiles form bubbles that can accelerate magma fragmentation.
Tephra : All fragmental material ejected by a volcano, from fine ash to large blocks and bombs. Tephra deposits record where explosive ejecta fell and how much accumulated.
Pinatubo eruption of 1991 : A large 1991 eruption of Mount Pinatubo in the Philippines that injected ash and sulfur dioxide into the atmosphere. Monitoring and evacuation reduced casualties despite the eruption’s immense scale.
Hawaiian eruption : An eruption style marked by relatively fluid lava fountains and flows, typically with low explosivity. Low-viscosity magma often lets gas escape more readily than in explosive eruptions.
Lahar : A rapidly flowing mixture of water and volcanic debris that travels down valleys and river channels. Eruption deposits can become lahars when mixed with rain, snowmelt, or water.
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