優悠生活

Layer of life

The atmosphere is a mixture of gases 600 kilometers thick that surrounds the Earth's surface.

The main gases are nitrogen (78.1 percent) and oxygen (20.9 percent), which togeter make up 99 percent of the air we breathe.

The atmosphere is made up of four layers.

The lowest layer is the troposphere, which contains 80 percent of the atmosphere's gases and is where conditions are suitable for life.

It is about 12 kilometers thick and is where all our weather occure.

The temperature of the troposphere decreases as the height increases.

Then temperature atart to increase as height increases.

This is the beginning of the second layer, called the stratosphere, which extends to a heigt of aoubt 50 kilometers above the Earth's surface,

When you pass that height, the temperature starts to decrease again.

You have entered the nest layer, the mesosphere, which extends up to about 85 kilometers.

In the mesosphere, temperatures decrease with height to as low as minus 90 degrees Celsius.

As you pass a height of 85 kilometers, temperatures start rising again and you enter the top layer, the thermosphere.

Temperatures in the termosphere can rise to as height as 1700 degrees Celsius.

It extends to about 600 kilometers, although there is no abrupt end to it.

It gradually becomes thinner and thinner, fading away into the vacuum of outer space.

As well as providing the air we breathe, the atomosphere protects us from the sun.

Ultraviolet radiation from the sun is deadly to both plants and animals.

It can kill us by destroying DNA and breaking chemical bonds in living cells, causing skin cancers.

It also destroys cholorophyll, the pases of plant life.

We are fortunate that the stratosphere contains a layer of gas called ozone.

Ozone is a from of oxygen in which the molecules contain three atmos of oxygen (instead of the two atoms in most oxygen molecules).

This ozone layer in the stratosphere acts as a shield that absorbs the sun's ultraviolet radiation and thus protects all living things on Earth.

In the 1920s, gases called chlorofluorocarbons (CFCs) were developed for use in aerosols and refrigeration.

For decades they were considered safe.

By 1985 more than 1.8 million tonnes of CFCs had been released into the atmosphere.

However, in the atmosphere CFCs break down to form chlorine gas, which in cold, sunny conditions reacts with ozone and destroys it.

In the mid-1970s scientists startled to realize that an ozone hole was developing over the Antarctic.

In an ozone hole, the concentraion of  ozone is a lot lower than normal, letting ultraviolet radiation pass through.

The health of the atmosphere is essential to all life on Earth.

Unfortunately CFCs will remain in the atmosphere for alog time yet, and so it will take a long time for ozone leavels to recover.

The atmosphere is also being affected by the emission of gases from ohter human activities such as industry and the use of motor vehicles.

A major danger to our atmosphere is global warming, a problem which has still to be addressed serioysly.

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酸素の原子記号はO2

オゾンの原子記号はO3

大気圏は４つの層でできているそうです。

　　　熱圏　　　　　　　　　

 　　 中間圏　　　　　　　

　　　成層圏　　　　　　　　

　　　対流圏　　　　　　　　

あらためて、オゾン層の重要性を知りました。

地球温暖化を抑制を急がなければなりません、、、。