Page 21 - Super Earth Encyclopedia

ICELAND
In the far North Atlantic, a plume of EXPANDING OCEANS
heat rising through Earth’s mantle As new oceanic crust is formed in a
has produced enough magma to spreading rift, the ocean floor grows wider.
raise part of the Mid-Atlantic Ridge In 180 million years this has made the
above the waves. It forms Iceland, Atlantic Ocean grow from a narrow valley
famous for its volcanoes and geysers. to a broad ocean. The same process is in its
The whole island is made of basalt early stages in the Red Sea, a spreading rift
rock erupted from the spreading rift growing at about 0.4 in (1 cm) a year.
of the mid-ocean ridge—the same
dark, heavy rock that forms the
deep ocean floors.

Greenland

RED SEA
Ireland
The Red Sea has formed where the Arabian and
African plates are being pulled steadily apart.
It will eventually become an ocean.

The submerged edge of a
continent forms a shallow
continental shelf.

The ocean floor is
dotted with submarine
mountains up to 13,000 ft
(4,000 m) high.

Spain

Away from the ridge,
the ocean floor is
covered with deep PILLOW LAVA
layers of soft sediment.
Molten rock erupting on
the ocean floor hardens
on the outside as soon as it
hits the cold water. But internal
Africa pressure makes it burst
through the hard shell to form
a series of rounded lobes.
When these finally solidify,
they are called pillow lavas.
Continental crust rock is
lighter than mantle rock, UNIQUE EARTH
so it floats on top of it.

The mantle rock is very
New oceanic crust is formed where hot but normally kept
magma wells up and hardens in the rift. solid by pressure.
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