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Introduction

A volcano is a location where magma, or hot melted rock from within a planet, reaches the surface. It may happen violently, in a massive supersonic explosion, or more quietly, as a sticky, slow lava flow.

Volcanoes have been a part of earth's history long before humans. Compare the history of human beings, a few million years in the making, to that of the Earth, over four billion years in the making. Volcanoes were important contributors to the early earth atmosphere by releasing gases such as nitrogen (N2), carbon dioxide (CO2), and ammonia (NH4).

Volumes of Some Well-Known Volcanic Eruptions

  Eruption                      Date           Volume in km3
  --------                      ----           --------------
  Paricutin, Mexico             1943                 1.3
  Mt. Vesuvius, Italy           79 A.D.               3
  Mount St. Helen, Washington   1980                  4
  Krakatoa, Indonesia           1883                 18
  Long Valley, California     pre-historic       >450 & <700
  Yellowstone, Wyoming        pre-historic           2400
Note that volcanic eruptions that occurred before historic times were several orders of magnitude larger (more than 1000 km3 in erupted volume) than ones observed by humans.
Volcano Web : Introduction

created by Lorrie Lava, lava@pele.bigu.edu
Volcanic Studies, Big University

last modified: April 1, 1995

URL: http://www.bigu.edu/web/intro.html