Popocatépetl emerged in the crater of other volcanoes in its current form more than 20,000 years ago and has been active since 1994, spewing plumes of smoke, gas and ash more or less daily. The ...
One of the most explosive volcanoes in U.S. history began its eruption with a trickle, not a blast. Mount St. Helens' gas-laden magma oozed into the cone before the mountain finally erupted in 1980.