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The Question

(Submitted April 03, 1998)

What if our Ozone Layer had a very large hole in it, enough to cover Australia?

The Answer

The ozone layer blocks out harmful ultraviolet (UV) rays from the Sun. Where there is less ozone, more UV gets through. UV rays affect different plants and animals in different ways--just as some people tan while others burn, some species are more susceptible to damage from ultraviolet rays than others.

An ozone 'hole', a place where there the ozone layer is thinner than normal, was discovered a few years ago over Antarctica. Even at the ozone levels found in the hole, most of the UV light is blocked before it reaches the ground. But enough gets through to worry scientists.

The ozone hole is centered on Antarctica, so for it to stretch all the way up to Australia, it would have to be quite large. That means that much of the Antarctic Ocean and the Southern parts of other oceans would be exposed, and these regions are very important to the world ecology. This might harm some species of plankton and other ocean plants and animals. Nobody really knows which species are most susceptible, and which will thrive as the UV reduces the competition. The result might be worse (from our perspective) than the current situation, because the current situation is what we are used to--when something good changes, it usually becomes worse.

As for effects on individual people--an enlarged ozone hole would cause an increase in tanning, burning, and skin cancer. However, the amount of UV that gets through even 'normal' ozone layers is enough that it is wise to wear a hat and sunscreen if you want to reduce your risk of skin cancer and other effects.

More information is at http://ozoneaq.gsfc.nasa.gov/ozone_overhead_current_v8.md.

David Palmer
for Ask an Astrophysicist

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