The Coriolis Effect for Middle School Science

The Coriolis Effect is a small topic in atmospheric science that can be seen in big ways. It explains why hurricanes spin and why massive air currents bend. You can witness the Coriolis Effect by playing catch on a merry-go-round.

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The Coriolis Effect

What is the Coriolis Effect?

Hurricanes spin because of the Coriolis Effect. Global winds and ocean currents bend because of the Coriolis Effect. The Coriolis Effect causes large masses of air and water in the northern hemisphere to bend to the right, and large masses of air and water in the southern hemisphere to bend to the left. It does this because the Earth spins on an axis at different speeds. 

The Earth is shaped like a ball. The middle of the Earth, the equator, is wider than the ends of the Earth, the poles. The distance around the equator is about 25,000 miles, and the distance around the poles is about six feet. In both places, the Earth makes one full circle every 24 hours, but the Earth spins at about 1,040 miles per hour at the equator and just 0.00005 miles per hour at the poles. 

The water and air that sit on the surface of the Earth are also rotating at different speeds. When air and water at the equator move toward the poles, they are spinning faster than the land under them. Because the Earth is rotating from west to east, they deflect toward the right in the northern hemisphere and to the left in the southern hemisphere. 

The Coriolis Effect happens on any circular or spherical surface. If you spin a ball and try to draw a line from the middle of the ball to the top, you will see the Coriolis Effect. If you pass a ball to a friend on the opposite side of a spinning merry-go-round, you will see the Coriolis Effect. The Coriolis Effect is all around us.

The Atmosphere

Middle School Science