The danger area around a volcano covers about a 20-mile radius. Approximately 100,000 times as viscous as water, lava can flow large distances before cooling and solidifying because of its shear thinning and thixotropic properties.
A volcano is a mountain that opens downward to a pool of molten rock below the surface of the earth. When pressure builds up, eruptions occur.
In an eruption, gases and rock shoot up through the opening and spill over or fill the air with lava fragments. Eruptions can cause lava flows, hot ash flows, mudslides, avalanches, falling ash and floods.