A volcanic eruption occurs when gases and rocks are ejected from a volcano. They can come from side branches or from the top of the volcano. This can cause severe damage. Several types of volcanic eruptions have been described by volcanologists. These are often named after famous volcanoes where that type of eruption has been seen. Some volcanoes may show only one characteristic type of eruption during a period of activity, while others may show a range of types all in one eruptive series.