Knowra Volcanic eruption Volcanic eruption A volcanic eruption releases magma, gases, and fragmented material from a volcano. Eruptions range from slow lava outpourings to explosive blasts that send ash and gas into the atmosphere.
Magma : Molten or partly molten rock beneath Earth's surface, containing crystals and dissolved gases. Its composition, temperature, and viscosity help determine whether magma rises gently or explosively.
Mount St. Helens eruption of 1980 : A major explosive eruption of Mount St. Helens in Washington State on May 18, 1980. Its landslide-triggered blast demonstrates how flank collapse can intensify an eruption.
Volcano monitoring : The systematic measurement of volcanic activity to detect changes that may precede or accompany eruptions. Changes in earthquakes, ground shape, and gas emissions can signal rising magma.
Pyroclastic flow : A fast-moving, ground-hugging current of hot gas, ash, and volcanic fragments. This highly destructive hazard can race down a volcano during explosive eruptions.
Effusive eruption : An eruption dominated by the relatively gentle outpouring of lava. It contrasts with eruptions that violently fragment magma into ash and pumice.
Volcanic gas : Gases released from magma, chiefly water vapor, carbon dioxide, and sulfur dioxide. As magma rises and pressure falls, expanding gases can fragment it and drive explosive activity.
Mount Pinatubo eruption of 1991 : A large explosive eruption in the Philippines that injected sulfur dioxide into the stratosphere. It illustrates how eruption columns can affect climate far beyond the volcano.
Volcanic earthquake : An earthquake caused by moving magma, volcanic fluids, or processes within a volcanic system. Earthquake patterns help identify magma movement and changing activity beneath a volcano.
Lahar : A destructive flow of water mixed with volcanic ash and debris. Eruptions can melt snow or mobilize loose deposits, sending lahars far down river valleys.
Explosive eruption : An eruption that violently ejects gas, ash, and fragmented volcanic material. It contrasts with lava-dominated activity in which magma escapes without extensive fragmentation.
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