MadSci Network: Earth Sciences

Re: were tornados always happening in the midwest?

Date: Tue May 24 14:22:25 2005
Posted By: Ken Harding, Science and Operations Officer
Area of science: Earth Sciences
ID: 1116290550.Es

Hello Myrtle,

The occurrence of tornadoes is not restricted to the central plains of the United States. Every state in the U.S. has reported tornadoes. Tornadoes also occur in Australia, Korea, Europe, Canada and Russia. However, the vast majority of them occur in the area roughy bounded by the Rocky Mountains in the west, Texas in the south, North to the Dakotas, and east to the Appalachian Mountains; the so-called Tornado Alley.

Conditions in this general area are especially favorable for large numbers of tornadoes. These conditions include:

When the continents were in a different configuration, these favorable conditions may not have been met in what was to become the central plains of the US, but they easily could have been met on another continent that would have had these conditions. Also, as the earth’s climate has changed, weather patterns, including tornadoes, have changed.

Our written weather records for tornadoes don’t really start in the central plains until the late 1800’s when more people began to settle. I have included the oldest known picture of a tornado, taken on August 28, 1884 near Howard, South Dakota (below).

Tornadoes require a special set of atmospheric conditions to occur regularly. The central plains of the U.S. have these conditions, and probably have had them as long as the North American continent has been relatively close to its present position, and as long as the climate has been similar to now. My best estimate is the the central plains have been a ‘Tornado Alley’ since the last ice age, approximately 10,000 years ago. (

Oldest known tornado photo

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