Knowra Volcanic risk Volcanic risk Volcanic risk is the likelihood and consequences of harm to people, infrastructure, and other valued assets from volcanic hazards. It depends on the hazards, exposure, vulnerability, and capacity to respond.
Volcanic hazard : A potentially damaging process or phenomenon produced by volcanic activity. The physical processes that can cause harm are the hazard side of volcanic risk.
Volcanic ash : Fragments of volcanic rock and glass smaller than two millimeters, ejected during explosive eruptions. Ash can spread far beyond an eruption and disrupt health, transport, power, and water systems.
Volcanic hazard map : A map showing areas that could be affected by specified volcanic hazards. Hazard maps help identify exposed places and inform land-use and evacuation plans.
1985 Nevado del Ruiz eruption : An eruption in Colombia that generated lahars which devastated Armero and killed more than 20,000 people. The disaster demonstrated how warnings can fail to protect highly exposed communities.
Exposure (risk) : The presence of people, infrastructure, or other valued assets in places that could be affected by hazards. A hazard creates risk only where people or assets are exposed to it.
Pyroclastic density current : A fast-moving mixture of hot gas, ash, and volcanic fragments that flows along the ground. Its speed, heat, and reach make it a major source of immediate life-safety risk.
Volcano alert level : A standardized status indicating the level of volcanic activity and associated public concern. Alert levels communicate changing conditions, but do not by themselves specify local risk.
1980 Mount St. Helens eruption : A major eruption in Washington State that caused a lateral blast, widespread ashfall, and 57 deaths. Its consequences illustrate how sudden eruption dynamics can overwhelm hazard-zone expectations.
Vulnerability : The conditions that make people or assets more susceptible to harm from a hazard. Differences in vulnerability help explain why the same hazard causes unequal losses.
Lahar : A flowing mixture of water and volcanic debris that travels down valleys and river channels. Lahars can threaten communities far from a volcano, including after an eruption ends.
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