Knowra Volcanic hazard Volcanic hazard A potentially damaging process or condition produced by volcanic activity. Hazards include fast-moving flows, airborne materials, toxic gases, and longer-term effects.
Pyroclastic density current : A fast, ground-hugging mixture of hot volcanic gas, ash, and rock fragments moving downslope. These currents can overwhelm communities through heat, impact, and burial within minutes.
Volcanic hazard map : A map showing areas potentially affected by specified volcanic hazards. Maps translate likely flow paths, ashfall, and inundation into zones for land use and emergency planning.
Mount Vesuvius : A volcano near Naples, Italy, known for its AD 79 eruption that buried Pompeii and Herculaneum. The eruption illustrates how ashfall and pyroclastic surges can devastate settlements.
Tsunami : A series of long ocean waves generated by sudden displacement of a large volume of water. Volcanic collapses or explosions can trigger tsunamis, but many tsunamis have nonvolcanic causes.
Lahar : A volcanic mudflow or debris flow composed of water and volcanic sediment. Lahars can travel far beyond a volcano, including along river valleys after an eruption.
Volcanic alert level : A communication scale describing a volcano's current activity and associated public threat. Alert levels help authorities communicate changing conditions, though they do not predict exact eruption outcomes.
Nevado del Ruiz : A Colombian stratovolcano whose 1985 eruption melted ice and generated lahars that buried Armero. The disaster demonstrates the reach and lethality of eruption-triggered lahars.
Earthquake : Sudden ground shaking caused by the rapid release of energy within Earth's crust. Volcanoes can produce earthquakes, but tectonic earthquakes also occur independently of volcanic activity.
Volcanic ash : Fragments of volcanic rock and glass smaller than two millimeters, blasted into the atmosphere during eruptions. Ashfall can damage lungs, machinery, crops, roofs, and aircraft over broad areas.
Volcano monitoring : The observation of volcanic activity using seismic, deformation, gas, thermal, and other measurements. Monitoring can reveal unrest and support timely warnings before some hazardous events.
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