The New Childrens Encyclopedia

PROTECTING EARTH

The atmosphere plays a vital role

in protecting life on Earth. It

absorbs much of the Sun’s

harmful rays but allows

enough through to warm

up the planet. It protects the

planet from meteor showers.

The atmosphere also holds oxygen

and water, which are essential for life.

, WHAT’S IN THE AIR?

Around 20 percent of the

atmosphere consists of oxygen,

which we need to breathe.

Most of the rest is nitrogen,

but a tiny fraction is made up

of other gases, such as carbon

dioxide and methane.

TAKE A LOOK

The atmosphere consists of

five layers—the troposphere,

stratosphere, mesosphere,

ionosphere, and exosphere.

Other gases

, TIGHT SQUEEZE Gravity

squeezes 99 percent of the gases

in the atmosphere into the first

25 miles (40 km) above Earth’s

surface. The rest extends 600 miles

(1,000 km) out into space.

■ Ozone forms a thin layer

around Earth, about 15 miles

(25 km) above the surface.

■ The ozone layer protects

life from the harmful ultraviolet

(UV) radiation in sunlight.

■ Harmful gases in aerosols and other

systems destroy ozone, creating holes in

the ozone layer over the polar regions.

OZONE LAYER

Atmosphere

Life on Earth could not exist without the thick blanket

of gases that surrounds the planet. This “atmosphere” is a

complex, dynamic system that interacts with the oceans,

land, and the Sun to create our weather and climate.

u HOLE A satellite

image reveals the

ozone hole (purple).

Oxygen

Nitrogen

EXOSPHERE

IONOSPHERE

MESOSPHERE

STRATOSPHERE

TROPOSPHERE

Airplanes

Shooting

stars

Space shuttle

Satellites

EARTH

A satellite orbiting

Earth at an altitude of

roughly 12,500 miles

(20,000 km) will be

traveling at an

amazing 8,500 mph

(14,000 km/h).

W

OW!

300 miles (500 km)

50 miles (80 km)

30 miles (50 km)

6 miles (10 km)

Clouds

Northern

lights