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The Coriolis effect is named after Gustave Gaspard Coriolis, a 19th-century French professor of mechanical engineering. He calculated much of the mathematics behind the effect. The theory explains the apparent deviation in the path of winds and water currents across the earth. Although Coriolis’ interest was in the various forces acting upon rotating pieces of machinery, the Coriolis effect is a topic in earth, environmental, and marine science. The effect can be a tough concept to explain, but it is fairly easy to model. The phenomenon can be demonstrated with a simple and inexpensive balloon activity.
Because the earth rotates (from west to east around a north-south axis), paths of objects moving great distances across the earth’s surface are deflected. If a plane left the North Pole, flying south toward Portland, Maine, and maintained that straight-line path for a period of time, the pilot might actually land in Portland, Oregon instead. From the perspective of a person standing in Portland, Maine, who had somehow been able to watch the entire flight, the plane would have veered far to the west, or to the right of the straight path, as seen from the North Pole. Similarly, both Anchorage and Los Angeles rotate once in a 24-hour day. Los Angeles “travels” farther and faster in that time period because it is on a lower latitude. Students need to picture this phenomenon clearly before they can comprehend the Coriolis effect and its impact on weather systems and ocean currents.
This activity takes approximately 15 minutes to complete. You can assess student understanding with the questions and answers provided. The extension activities introduce the meteorological and oceanographic applications of the activity.
The activity addresses these dimensions of the Next Generation Science Standards*(NGSS):
Science and Engineering Practices | Disciplinary Core Ideas | Crosscutting Concepts |
Practice: Developing and using models • Students will model the apparent deflection of a straight path known as the Coriolis effect. |
DCI: ESS2-Earth’s systems • Students will understand that the Coriolis effect helps explain the motions of both weather systems and ocean currents. |
Concept: Cause and Effect: Mechanism and explanation • Students will understand that the rotation of the earth explains the apparent deflection of a straight-line path. |
Students may struggle with understanding that the direction of the earth’s movement is based on their point of view. When they describe the direction (left or right) that the “straight” lines veer, make sure that the students determine this direction from the perspective of the beginning point of the line. Take a few minutes to discuss this as a class. You may also address common misconceptions concerning the Coriolis effect, such as the notion that the direction of swirl in a flushing toilet differs in the northern and southern hemispheres.
*Next Generation Science Standards® (NGSS) is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, these products.