A volcano is a special kind of mountain that contains an opening in the middle leading to a pool of molten rock, called magma, underneath the ground. When pressure increases to a certain amount, the volcano erupts. Many people know that a volcanic eruption causes hot lava to flow over the top of the volcano, but eruptions can also cause floods, mudslides, avalanches and falling ash. An active volcano's danger zone extends about 20 miles in all directions.Continue Reading
Falling ash from volcanic eruptions is dangerous because it can cause lung damage in babies, elderly individuals and people with respiratory conditions. The ash is comprised of pulverized rocks.
There is a huge amount of variability in the time it takes a volcano to grow. Some form within a night, while others take thousands of years to develop. At any given point in time, there are about 20 volcanoes erupting.
There are four categories of volcanoes: active, dormant, erupting and extinct. Scientists consider a volcano active if it has erupted within the past 10,000 years, and such a volcano may be either dormant or erupting. The volcano is dormant whenever it is not currently erupting, but scientists expect dormant volcanoes to erupt in the future. Extinct volcanoes have not erupted within the past 10,000 years, and scientists do not anticipate them erupting again, at least within a similar time frame.Learn more about Volcanoes