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Article: Earth, Planet
- Article from:
- World of Earth Science
CopyrightCOPYRIGHT 2003 The Gale Group, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Earth, planet
Earth is the third of nine planets in our
solar system
. Its surface is mostly
water
(about 70%), and it has a moderately dense nitrogen and
oxygen
atmosphere that supports life. Rich in
iron
and nickel, Earth is a dense, molten oblate sphere with a solid core and a thin outer
crust
. Earth rotates about its
polar axis
as it revolves around the
Sun
. Earth has one natural
satellite
, the
Moon
. A complete
revolution
of Earth around the Sun takes about one year, while a
rotation
on its axis takes one day. The surface of Earth is constantly changing, as tectonic plates slowly move about on the turbulent foundation of partially molten
rock
beneath them. ...