Volcanoes are steep hills or mountains formed by an accumulation of molten rock forced through openings in the earth’s crust. These volcanic vents, or openings, are referred to as volcanoes when actively spewing magma (molten rock).
Editorial Research Reports, October 21, 1983.
Magill, Frank N., ed. Magill’s Survey of Science: Earth Science Series, 1990.
McGraw-Hill Encyclopedia of Science and Technology, 1992.
The New Book of Popular Science. Grolier, 1994.
Ritchie, David. The Encyclopedia of Earthquakes and Volcanoes, 1994.
Simkin, Tom, and Lee Siebert. Volcanoes of the World, 1994.
EBSCO Magazine Article Summaries
NewsBank and other newspaper indexes
SIRS (Social Issues Resources Series)