WHAT WOULD IT BE LIKE WITHOUT AN OZONE LAYER?

Q. What would happen if we had no ozone layer?

C.C., Peabody, Mass.

A. Without an ozone layer, it would be a very different world — likely one without life as we know it.

Ozone is a gas that collects in a thin layer in the upper atmosphere and shields the Earth from ultraviolet radiation that is devastating to many life forms.

Early in Earth's history, before life crawled out of the oceans, there was no ozone layer. Ozone appeared only after plants started photosynthesizing and sending oxygen into the atmosphere. Ozone is created when molecules of oxygen, which are composed of two atoms and have the chemical formula O2, break into individual oxygen atoms and recombine into three-atom molecules of O3, or ozone. This can happen as a result of lightning's passing through the atmosphere or by other processes.

The ozone filters out ultraviolet-B, a type of invisible radiation from the sun that is extremely damaging to DNA and living cells.

"Many people believe the ozone layer allowed life as we know it to come out from the ocean and from under the rocks," says Kevin Gurney of the University of California.

Experiments show that ultraviolet B radiation can damage DNA, and field experiments show that reproduction is disrupted in amphibians in areas where ozone is thinning and more ultraviolet B is reaching the ground. With no ozone, radiation would be "fa r too intense and harsh" for life says Gurney.

"I don't think you'd have green life on this planet," says John Passacantando, executive director of Ozone Action, a Washington D.C.-based environmental group. "Mammals would go blind. Humans would have to walk around in space suits."

A world without ozone would be similar to world after nuclear fallout. While it wouldn't be hotter, radiation would cause skin cancer and cataracts and would disable our immune systems. We would have to battle blindness, disease, and then starvation, as p lants and animals started to die under the radiation's toxic effects, said Gurney.

We don't face the loss of our entire ozone layer. But chemicals such as chlorofluorocarbons, or CFCs, used in refrigeration, have caused a thinning of the layer over both poles. While many CFCs have been banned, Passacantando says the continued use of the chemicals in developing nations and by those who buy them on the black market poses a serious threat to the ozone layer.

Q. Why are the rocks redder in Arizona than in Massachusetts?

C.P, Peabody

A. Those dramatic red landscapes in Arizona are caused by "geologic rust," says Robert Butler, a professor of geologic sciences at the University of Arizona in Tucson.

Many of Arizona's rocks are formed largely of a mineral called hematite, which is a chemical combination of iron and oxygen. When this mineral is exposed to the elements, it rusts and turns red. "Hematite is the dominant material that makes rocks in Monument Valley red," says Butler. "It's a dramatic pigment."

Hematite occurs in sedimentary rocks, which are made of sediments that are carried in streams and then deposited in broad flood plains or shallow swamps. This was the scenario in many areas of Arizona in the geologic past.

Massachusetts rocks might not be as dramatic, but the state does have some red rock. They're known as "red beds," says Laura Brown, a geophysics professor at the University of Massachusetts at Amherst.

You'll find them in the Connecticut River Valley, near Interstate 91 in the Greenfield and Springfield areas, says Brown. These rocks, like those in Arizona, are sedimentary rocks formed in shallow lakes and swamps, says Brown. Like those of the West, the y owe their color to hematite.

"You might have to get close to see them," says Brown. "Ours aren't bright red." Massachusetts rocks are less brilliant, says Brown, because they've been weathered a good deal more, and they're also often covered with or stained by vegetat ion.

"We don't have that problem," says Arizona's Butler. "Ours are naked and all there for us to see."

Publication Date : 1998-01-27

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