The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
A tornado is a vortex or powerful whirling wind, often visible as a funnel-shaped cloud hanging from the base of a thunderstorm. It can be very violent and destructive as it moves across land in a fairly narrow path, usually a few hundred yards in width. Wind speeds are most often too strong to measure with instruments and are often estimated from the damages they cause. Winds have been estimated to exceed 350 mph (563 kph). Very steep pressure gradients are also associated with tornados and contribute to their destructiveness. Sudden changes in atmospheric pressure taking place as the storm passes sometimes cause walls and roofs of buildings to explode or collapse.
In some places such storms are referred to as cyclones. Tornados most frequently occur in the United States in the central plains where maritime polar and maritime tropical air masses often meet, producing highly unstable atmospheric conditions conducive to the development of severe thunderstorms. Most tornados occur between noon and sunset, when late afternoon heating contributes to atmospheric instability.