The image of the Mt. St. Helens volcano erupting and devastating hundreds of square miles of Pacific Northwest wilderness in 1980 remains a powerful memory for those of us old enough to remember the television news coverage of this major geological event. The story of Earths evolution contains many instances of volcanic eruptions, eruptions that altered the planets physical environment. The after effects of the eruption of Tambora in 1815 created the Year Without a Summer in the Northern Hemisphere the following year. The eruption of Tambora on Sumbawa Island, Indonesia, was the largest eruption in historic time. About 150 cubic kilometers of ash were eruptedabout 150 times more than the 1980 eruption of Mount St. Helens. Ash fell as far as 800 miles (1,300 km) from the volcano.
Earth isnt the only world with volcanoes, active or extinct.
Our nearest neighbor in space, the Moon, is covered with hundreds of volcanic features from cinder cones to vast lava fields.
While most of the lunar craters we see from Earth are the result of cosmic impacts, over 20 percent of the Moons physical features were actually formed by volcanic action. The great dark seas of the Moon, called maria in Latin, are vast plains of basaltic lava.
Planetary scientist Carlie Pieters of Brown University has discovered some volcanic features on the Moon that may be less than a million years old. Astronomers have even witnessed possible real-time volcanic events, such as the famous eruption in the lunar crater Alphonsus in November 1958. Astronomer Nikolay A. Kozyrev witnessed a pyroclastic volcanic eruption near the central peak of Alphonsus.
The planet Venus, blanketed in a thick atmosphere of carbon dioxide, nitrogen and sulphuric-acid gases, is riddled with thousands of volcanic featuresfrom large shield volcanoes to pimple-like pancake dome volcanoes similar to, but vastly larger than, Californias Mono Lake volcanic domes. Some scientists believe Venusian volcanism contributes to the planets soaring 800-degree F surface temperature.