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The Spring 2011 issue of The Earth Scientist is focused on modernizing seismology education. Thanks to IRIS, you can download this issue for free as a pdf. Print copies are available in our online store.
The landscape and weather change greatly during the year in regions that have four distinct seasons.
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Images Courtesy of Corel

What Causes the Seasons?

The Earth's orbit is in the shape of an ellipse (a stretched out circle), so that sometimes the Earth is closer to the Sun than at other times. Is this the cause of the seasons?

You can imagine that if the seasons were caused by the Earth's orbit, people who live north of the Equator (in places like the North America, Europe and Asia) and people who live south of the equator (in places like South America, Australia, and Africa) would have the same seasons. For example, if winter occured because the Earth was far away from the Sun, everyplace on the Earth would be cold at the same time.

But this is not what happens! Summer in the north occurs at the same time as winter in the south, and vice-versa. It turns out that the Earth's orbit is nearly a perfect circle, and the difference between its smallest distance from the Sun and its largest distance is very small. In fact, the Earth is furthest away from the Sun in June when it is summer in the north!

The Earth is a very special planet in many ways. Just as Earth's unique atmosphere and its distance from the Sun work together to make Earth the right temperature to support life, Earth's orbit and its rotation work together to create the seasons.

Last modified June 26, 2008 by Vanessa Pearce.

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The Summer 2010 issue of The Earth Scientist, available in our online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.

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