A volcano is a vent which molten rock escapes through to the surface of the earth. An eruption happens when pressure from gases within the molten rock becomes too great. There may be lava flows, flattened landscapes, poisonous gases, flying rock and ash.
Because of their intense heat, lava flows are great fire hazards. Lava flows destroy everything in their path, but most move slowly enough that people can move out of the way.
Fresh volcanic ash, made of pulverized rock, can be abrasive, acidic, gritty, gassy, and odorous. While not immediately dangerous, the acidic gas and ash can cause lung damage to infants, older adults, and individuals with severe respiratory illnesses.
Volcanic eruptions can be accompanied by other natural hazards, including earthquakes, mudflows and flash floods, rock falls and landslides, acid rain, fire, and tsunamis. Even a volcano thought inactive can suddenly erupt. Pay attention to any reports of volcanic activity and be prepared for any possible eruption.

If You Live, or Are Visiting, Near a Volcano:

Areas near a volcano will normally have a well known community warning system for the area. Make sure you are familiar with it. It is highly unlikely that a volcano will erupt violently without any warning. So you will usually have time to receive the warning and evacuate the area as soon as possible. Make sure, now, that you have a pre-arranged safe place to evacuate to, that you have an evacuation plan and that you have an evacuation survival kit ready to take with you.

Do not try to endure an eruption by staying in your home. Lava flows can trap you so that there is no escape. Ash and other debris can cover or strike you. Lahars (a wave of volcanic mudflow), landslides, flash flooding, hot muddy water, and chunks of debris can destroy your home. Volcanoes can also cause other disasters like earthquakes, so prepare for these as well.

During a Volcanic Eruption

If you are outdoors during an eruption, get indoors as soon as possible and close all doors and windows. Stay away from windows, which may get shattered by flying debris.