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Active and Dormant Volcanoes
A volcano that is erupting or has erupted
during historic times is called active. A Volcano in which there is
no evidence of any activity is considered extinct. Volcanoes that appear recent but have
no recorded
activity other than the quiet escape of gas are called dormant.
Some volcanoes are much more active than others. Stromboli, in the
Lipari Islands near Sicily, has been
constantly active since ancient times. Many active volcanoes are found in a belt, called
the Ring of Fire, that
circles the Pacific Ocean. Yet other volcanoes, such as Mount Vesuvius, continue in a
state of activity for
longer or shorter periods and then become dormant. The eruption that follows long dormancy
is violent.
This was shown in the 1980 eruption of Mount Saint Helens in the state of Washington. It
had been
dormant for a period of 123 years of being in a dormant state. The danger to life posed by
active volcanoes
is not limited to eruption of molten rock or showers of ash and cinders. Mudflows are also
equally
troublesome. A mudflow triggered by an eruption that melted ice and snow on Colombia's
Nevado del
Ruiz volcano in 1985 killed more than 25,000 people.