What is a Volcano?

For the catastrophic event I chose the volcanic eruption, because the eruption of the Mt. Saint Helens was always in my curiousity. Volcanic eruptions usually occur when the hot magma that’s been rising steadily finally pushes it’s way out of the earth’s crust. The occurrence of the eruption is totally dependent on the volcano itself. For example Mt. Kilauea almost never stopped erupting while Mt. Pinatubo hasn’t erupted since 1991. When the eruption occurs, the area affected by the volcano is very dependent on the magnitude of the volcanic eruption. For example if the volcanic eruption is very weak, it will only affect up to the county level; however, if the volcanic eruption is categorized as huge, it can affect the whole coastal zone. People are usually aware of the eruption months before it happens by the geological changes. For example Mt. Saint Helens started moving towards Seattle each month until it erupted.