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Continents
ALMOST ONE-THIRD OF THE SURFACE of Earth is land. There are seven vast
pieces of land, called continents that make up most of this area. The rest consists
of islands, which are much smaller landmasses completely surrounded by water.
The seven continents are crowded into almost one-half of the globe; the huge
Pacific Ocean occupies most of the other half. The largest continent is Asia,
which has an area of more than 17 million sq miles (44 million sq km).
Most scientists now agree that, about 200 million years ago, the
continents were joined together in one huge landmass. Over
millions of years they drifted around and changed shape,
and they are still moving today. The continents lie on vast
pieces of solid rock, called plates, that collide and move
against one another. These movements
cause volcanoes and earthquakes, push
up mountains, and create
huge trenches in
Earth’s crust.PLATE TECTONICS
The continents and oceans lie on top of several huge
plates of rock about 60 miles (100 km) deep.
These plates float on the hot, semi-molten
rock in the mantle underneath. Heat from
Earth’s interior makes the plates move,
carrying the continents with them.
Mountains and undersea ridges,
deep trenches, and huge valleys
form at the edges of the plates
as they move and collide.3
THE WORLD TODAY
The Americas have
moved away from the
other continents and
joined together, and India
has joined Asia. Australia
and Antarctica have
drifted apart.SAN ANDREAS FAULT
The San Andreas fault in
California is at the border
between two plates. They slide
against one another, causing
severe earthquakes.MOVING PLATES
The plates
move about
1 in (2.5 cm)
every year—
about as
fast as your
fingernails
grow. The
Atlantic Ocean
is widening at this speed,
as the Americas drift
apart from Europe
and Africa.Find out more
Earth
Earthquakes
Geology
Mountains
Oceans and seas
VolcanoesNazca
plate1
PANGAEA
The continents were joined in
one supercontinent, called Pangaea,
which began to break apart about
200 million
years ago.
The
continents
are made of
many smaller
pieces of land that
have been pushed
together.
CONTINENTAL DRIFT
A glance at the globe shows that the
eastern sides of North and South America
and the western sides of Europe and Africa
follow a similar line. In 1912, Alfred
Wegener, a German meteorologist,
suggested that the continents once fitted
together like pieces of a jigsaw puzzle. This
huge piece of land then broke up, and the
continents drifted apart.PANGAEAAsia
EuropeSouth
America
AfricaIndia
AustraliaAntarcticaGONDWANALANDEuropeAustralia
AntarcticaIndiaSouth
AmericaAfricaIndian
OceanIndian
plateAfrican
plateTrenchMolten
rock from
Nazca plate
forces its way up,
forming volcanoes
along edge of
continent.Nazca plate
moves under
South American
plate, forming
trench in
ocean floor.Pacific
OceanMantleHot rock rises from below,
pushing the American and
African plates apart and
forming an undersea ridge.AfricaNorth
America2
BREAKUP
About 135 million years ago,
Pangaea split up into two areas—
Gondwanaland and Laurasia.LAURASIANorth
AmericaAsiaUndersea
ridgeSouth
AmericaMountains and
volcanoesAtlantic
OceanAmerican
plateEurope
AsiaAfricaAntarcticaAustraliaNorth
AmericaSouth
America