Childrens Illustrated Encyclopedia

357

Continents Collide and grind against one another,

while hot, molten rock bubbles beneath earth’s surface.

these powerful forces thrust up mountains reaching as

high as 5 miles (8 km). Many mountains are still growing,

and those that formed long ago are slowly wearing

away. some mountains are volcanoes, made of layers

of so lid i fied lava that build up as the volcano erupts.

there are mountains under the oceans and on other

planets. the highest known mountain is on Mars;

it is three times as high as Mount everest.

earth has two vast mountain ranges. the Rocky

Mountains and the Andes run through north

and south America; the mighty Himalayas,

Alps, and Atlas Mountains stretch across Asia,

europe, and north Africa. these mountains

are “young”: they formed during the last 50

million years. other ranges, such as the Urals

in Russia, are much older and lower. the

forces of erosion have worn them down

since they were first formed more

than 200 million

years ago.

MoUnt eveRest

the world’s highest

mountain is Mount everest,

on the border of China and

nepal. it rises to 29,029 ft

(8,848 m). Above are

edmund Hillary of new

Zealand (left) and tenzing

norgay of nepal, who first

climbed everest in 1953.

AvAlAnCHe

snow and ice can

suddenly crash down a steep

mountainside. this is called an

avalanche, and it often occurs

in the spring as the snow melts.

MoUntAin CliMbing

Mountain climbing

requires special

equipment, such

as ropes to prevent

falls, and crampons—

steel spikes attached

to mountaineers’

boots that

grip ice.

eRosion

ice, wind, and running water break

up rock, slowly wearing it away over

millions of years. this process of

erosion carves out deep valleys and

creates high peaks. Continuing

erosion wears away the peaks, so

that the mountains become

lower and more rounded.

MoUntAin Zones

A high mountain has several zones, or

regions, containing different kinds of plants.

Forests cover the mountain’s lower reaches.

Farther up is a zone of small, low-lying

plants. snow covers the summit, which is

bare of plant life. Zones occur because the

air becomes colder higher up the mountain.

Forests of broad-

leaved trees and a wide

range of other vegetation

grow at the base of

the mountain.

FAUlting And Folding

As the continents move, they

squeeze layers of rock. these

movements produce huge

cracks, or faults, and push

up blocks of rock that

form block mountains. the

movements also make earth’s

surface buckle, form ing fold

mountains. dome mountains

appear when molten granite

pushes the rock above it into

a huge hump.

Formation of

block mountains

High on the

mountaintop it

is so cold that

plants cannot

grow. There

is only snow

and bare

rock.

Formation of fold

Mountains

Mountains

Block wears away

over many years to

produce a mountain.

Squeezing action

pushes up

blocks of rock.

The rocks then

crack and

wear away at

the top of the

curve, forming

jagged mountains.

As layers of rock

are squeezed, they

form zigzag folds.

Find out more

Continents

glaciers and ice caps

Mountain wildlife

oceans and seas

volcanoes

Higher still, only

plants that are

adapted to the cold

are able to grow.

Forests of pine

trees grow higher

up the mountain

where it is colder.

US_357_Mountains.indd 357 22/01/16 11:12 am