Page 20 - Oceans

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Size: 216 x 276 (Bleed5mm)
Size: 216 x 276 (Bleed5mm)
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18 Titles:E.Explore_Ocean (ED594) 1 018 000 18/04/07 1:30 NT1-6 Titles:E.Explore_Ocean (ED594) 1 019 000 18/04/07 1:30 NT1-6
oceans and continents
Ocean basins are not just water-filled hollows in the Earth’s
surface. They are quite different from the continents that
Upper mantle:
divide them. The heavy bedrock of ocean floors is the thin partly molten
rock, 416 miles (670
crust of the hot mantle that forms most of the planet, while km) thick; temperature
1,800°F (1,000°C)
continents are made of thicker slabs of lighter rock that
float on the mantle like rafts. The continents are dragged

slowly around the world by currents within the
mantle. Oceans form where continents are pulled
apart, and are destroyed where continents are

pushed together.
Inner core: solid metals
about 1,500 miles (2,440
km) across; temperature
THE LAYERED EARTH > 12,600°F (7,000°C)
The Earth was formed from asteroids that were
drawn together by gravity to form a rocky sphere. Outer core: liquid metals
As they collided they released enough energy to about 1,400 miles (2,250 km)
thick; temperature 7,200°F
melt the entire planet. Most of the heavy metal (4,000°C)
in the rock sank to the center to form its metallic
core. The rock around the core became the solid Lower mantle: solid rock,
but very hot mantle, and the skin of the mantle 1,400 miles (2,230 km)
cooled to form the Earth’s crust. thick; temperature 6,300°F
(3,500°C)
Continental shelf

Continental < the earth's crust
crust
The heavy, dark rock of the oceanic crust is similar to the
Oceanic crust rock of the upper mantle, and is just 4–7 miles (6–11 km)
thick. By contrast, the continental crust is up to 55 miles
Upper mantle
(90 km) thick, but its rocks weigh less than the rocks that form
Lower mantle the ocean floor. The continental shelves are the submerged edges
of the continents, drowned by shallow coastal seas.

mantle and crust rocks

peridotite basalt granite
The upper mantle is made Oceanic crust is made Continental crust is made up of many rocks, but one of
of peridotite, a very heavy rock that contains a lot of of basalt. This is basically peridotite that has lost some the most common is granite. It is formed from molten
iron and another metal, magnesium. Peridotite occurs of its heavier ingredients. Basalt erupts from oceanic rock that has cooled very slowly, deep in the ground.
in just a few places where it has been squeezed up from volcanoes as very liquid lava, which cools to form a black Granite has a lower metal content than basalt, so it is
beneath the ocean floor. rock that gradually turns rusty brown on the outside. lighter. This is why it "floats" on the dense, heavy mantle.