Lahar Hazard Zones for Eruption-Generated Lahars in the Lassen Volcanic Center, California

Lahars, Indonesian for volcanic mudflows or debris-flows, are a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano. Lahar generation requires an adequate source of water, abundant unconsolidated debris, steep slopes, significant relief, and a triggering mechanism (Vallance, 2000). Various triggering mechanisms include the rapid melting of snow and ice by pyroclastic flows, intense rainfall on loose volcanic rock deposits, a breakout of a lake dammed by volcanic deposits, and a debris avalanche.