Satellite image courtesy of NOAA
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
Each year thousands of schools in the United States participate in the National Geographic Bee using materials prepared by the National Geographic Society. The contest is designed to inspire students to be curious about the world. Schools with students in grades four through eight are eligible for this entertaining and challenging competition.
Registration for the 2015 Geo Bee has ended. Schools can register for next year's Geo Bee in August 2015.
School Geo Bees have all been held. Please mark your calendar for the upcoming State Geo Bee on March 27, 2015, in all 50 states and the District of Columbia. To find out the location of the State Geo Bee for your state, email us at firstname.lastname@example.org.
The national competition of the Geo Bee will be held May 11-13, 2015, at the National Geographic Society’s headquarters in Washington, D.C. It will be televised on May 15, 2015, at 8 p.m. on the National Geographic Channel and NG Wild.
Gain a Global Perspective
The 2014 National Geographic Bee finalists gush about geography.
How to Help
Donations help fund schools to participate in the National Geographic Bee.
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Springtime brings the possibility of extreme weather, including violent thunderstorms and tornadoes.