Childrens Illustrated Encyclopedia

Shaping the landScape

glaciers slowly grind away even the

hardest rock and reveal a changed

landscape when they retreat. deep

valleys and lakes, together with

rivers and waterfalls, now exist

where there were

none before.

236

Glaciers

Valley glacier

the ice fills a valley, moving

faster at the center than at

the sides of the glacier.

cracks called crevasses

open in the surface.

Frozen

mammothS

in the russian

Federation, ice and

frozen soil have preserved

huge hairy elephants, called

mammoths, just as if they

were in a deep freeze.

the last mammoths lived in

north america, europe, and

asia during the ice age.

moraine

the glacier acts like a huge

conveyor belt, carrying broken

rocks, called moraines, down from the

mountaintop. the moving ice also plucks

stones and boulders from the base and sides of

the valley. this material is carried along within

the glacier, and is called englacial moraine.

ice age

a deep ice sheet covered about one- third

of the world’s land during the last ice age.

ice extended as far south as Saint louis,

missouri, and london, england. there

had been ice ages before the last one,

and there could be more in the future.

Find out more

antarctica

arctic

mountains

polar wildlife

rain and snow

ice cap

ice caps cover

vast areas. When

the thickness of

the ice reaches

about 200 ft (60 m),

its enormous weight

sets it moving.

Rocks in the

melting ice build

up a wall called a

terminal moraine.

SnoW Falling on the world’s tallest mountain peaks never melts. the

temperature rarely rises above freezing, and fresh falls of snow press down on

those below, turning them to ice. a thick cover of ice, called an ice cap or ice sheet,

builds up, or snow collects in hollows. ice flows down from the hollows in rivers of

ice called glaciers. they move very slowly, usually less than 3.3 ft (1 m) a day, down

toward the lower slopes. there it is usually warmer, and the glaciers melt.

however, in the arctic and the antarctic, ice and snow remain throughout the

year, though in recent times, large areas of ice have been melting because

of global warming. ice sheets covered much of north

america and europe during the last ice

age over the last million years. When

the weather became warmer,

about 10,000 years ago, the

ice sheets retreated. ice

sheets now exist only in

greenland and antarctica.

and ice caps

glacierS

glaciers often join

together, just as small

rivers meet to form bigger

rivers. the ice may be

more than 0.5 mile

(1 km) deep.

FjordS

the sea rose at the end of the ice

age, drowning valleys formed by

glaciers. these deep, steep-sided

inlets are called fjords. the coast

of norway has many fjords.

Waterfall

Lake formed

behind

moraines

A river

flows down

the center of

the valley.

Streams of

water form as

the glacier melts.

Icebergs

huge pieces of

floating ice are

called icebergs.

nine-tenths of the

ice floats below the

water, so icebergs

are a danger to

ships. in 1912, the

ocean liner Titanic

sank after colliding

with an iceberg.

Deep

U-shaped

valley carved

out by

the glacier

cirqueS

the hollow

where the ice

collects to start

the glacier is

called a cirque

or corrie.

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