Photo: Infared satellite image of hurricane Rita

Infrared satellite image of hurricane Rita

Satellite image courtesy of NOAA

Download this activity as a PDF.

Springtime may bring the promise of April showers and May flowers. But it also brings the possibility of extreme weather, including violent thunder-storms and tornadoes.

Most countries experience tornadoes, but they occur more frequently in the United States, east of the Rocky Mountains, than anywhere else on Earth. On average, almost 1000 tornadoes touch down in the U.S. each year, leaving in their wake destruction and sometimes death.

How Tornadoes Form

Thunderstorms form when warm, moist air collides with an eastward moving cold front. These storms often produce strong winds, damaging hail, and even tornadoes. A tornado is a rapidly rotating column of air that extends from the base of a thunderstorm to the ground. A tornado’s characteristic funnel shape is visible because of water droplets, dust, and other debris that are caught up in the swirling air.

Measuring the Force of a Tornado

The force of a tornado is measured using the Fujita Scale, which ranks tornadoes based on the level of damage caused by the storm. The scale ranges from F-0 for a storm that causes light damage to F-5 for a storm that leaves incredible damage.

Mapping Tornado Frequency in the U.S.

a)  Distribute to students copies of the handout. Have student examine the data in the handout to identify which states average the highest number of tornadoes each year.

b)    Next, distribute blank U.S. maps. Have students construct choropleth maps showing the frequency of tornadoes by state in the U.S.

c)    Explain to students that areas with a high occurrence of tornadoes have been given the nicknames of “Tornado Alley” and “Dixie Alley.” Have them refer to their maps to locate these two regions that experience many tornadoes each year.

Extending the Activity

Divide the class into three groups and assign each group one of the following research topics. When students have completed their research, have each group report back to the class.

i. Structure of a tornado

ii. Fujita Scale

iii. Tornado Alley/Dixie Alley

See the NOAA National Severe Storms Laboratory and the Tornado Project for more information.


Teachers and Parents

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    State Bees

    On March 30, 2012 about 100 fourth to eighth graders in each of the 50 states faced off during the National Geographic state level bees.

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    Principals of schools in the U.S. with any of the grades four through eight are eligible to register their schools to receive contest materials for a school-level Bee.

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    Wondering how to register for the Bee or how to prepare? Our "Frequently Asked Questions" have the answers!

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    What's the best way for students to prepare for the Bee? Here are some tips from the National Geographic Bee.

Quizzes to Go

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    Now on Your Favorite Mobile Device!

    Do you have what it takes to be the next National Geographic Bee Champion? Find out the fun way with the new GeoBee Challenge! Three types of game play make sure you really know your stuff and never get bored.

Google Earth Presents

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    GeoBee: Geography

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Download Google Earth »

Student Activities

Teachers can use these activities in the classroom to prepare students for the bee!

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    Tracking Violent Storms

    Springtime brings the possibility of extreme weather, including violent thunderstorms and tornadoes.

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