Volcanoes erupt in different ways, pose multiple types of hazards, and the initiation and duration of eruptions is relatively uncertain. Therefore, authorities and populations at risk must be knowledgeable about regional volcano hazards so that they can be both prepared and flexible in their response. Location-specific volcano hazards information can be found on a volcano-by-volcano basis. Use this map to select the volcano or volcanoes nearest you to read about the hazards present.
The USGS has published several volcano-specific hazard maps, which illustrate the potential for ground-based volcanic impacts—lava flows, hot rocks, volcanic gases, and more far-reaching hazards such as ashfall and lahars that flow in valleys that drain the volcano.
In the event of an eruption, scientists will evaluate current events and develop "scenario" based hazards maps that depict possible scenarios for the progress of volcanic activity.
Become familiar with evacuation routes.
Typical volcano hazard zones during an eruption are:
- Areas immediately around the erupting volcanic vent.
- Areas downwind of the vent if the eruption produces ash.
- Areas downslope of the vent if the eruption produces lava flows.
- The stream and river valleys that drain the volcano if the volcano is covered in snow and ice.
Depending up the type of volcano, downslope communities may need to prepare for lava flows or lahars. Lava flows that impact people occur from basaltic volcanoes, like those in Hawaii. Lahars impact river valleys and typically occur from snow- and ice-clad volcanoes like those in the Cascade Range.
Downwind communities may need to prepare for tephra and ash fall. When ash-producing eruptions are imminent or in process, the USGS and its partners will analyze wind conditions and develop maps that indicate areas most likely to receive ash fall.