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Jump to: Intro,
Motions of the Earth,
Characteristics Page 1,
Page 2: Characteristics Page 2, Changes
CHARACTERISTICS
PAGE 2
Another
interesting feature of earth and other planets is that there is a
force called gravity. This is the force that causes objects to fall
if dropped. The earth and the planets travel around the sun because
gravity pulls them towards it. On earth, gravity is stronger at the
poles and at sea level.
We always hear about magnetic
poles, but what are they really? The earth spins around an imaginary
line that connects the north and the south poles. Near these poles
are the magnetic poles. These poles acts just as a bar magnet. The
north magnetic pole is on Ellef Ringnes Island in N. Canada. The
south magnetic pole is off the coast of Wilkes Land, a part of
Antarctica. It is believed that magnetism comes from the
"circulation of molten rock in the earth's outer core."
Magnetic force is present in the magnetosphere, a region shaped like
a teardrop. This magnetosphere acts on electrons and protons that
move throughout space and shields the earth from them.
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The magnetic poles of the Earth.
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CHANGES:
Our earth is changing
continuously. There are many types of changes, some that take a long
period of time and others that occur within a few minutes. There are
four main types of changes, weathering, erosion, mass movement and
crust changes.
Weathering is caused by water,
ice, chemicals, plants, and temperature changes. In this process
rocks are broken up and result in soil, rock and remains of living
organisms. There are two types of weathering known as physical and
chemical. Physical weathering breaks the rocks in to many pieces.
Water soaks in to cracks, and if the weather is low enough, the
water gets sealed in the cracks. When the water freezes, it expands
and can crack the rock. Chemical weathering affects the rocks and
soil components. It is caused by the dissolving action of water
which can cause rocks to crumble.
Erosion is partly related to
weathering. It is a combination of weathering and movement of the
material. Eroded substances move from high to low, such as from
mountains to valleys. It can be caused by water, glaciers, and wind.
Water combines weathering action and its ability to move rocks. When
rivers reach the sea, they leave behind materials in a triangular
deposit, known as a delta. Water changes the shape of the land
gradually. Water moving underground changes the land as well Geysers
come out of the earth and contain dissolved minerals. Wind moves the
dust and sand. It also carries ashes from volcanoes.
Mass movement is the slipping
of large amounts of rock and soil, such as in a landslide or in mud.
Landslides occur on steep hills or mountains. Weathering or erosion
loosens rocks and causes them to slide downhill. This may have a
variety of effects such as damming a river or widening a valley.
Crystal changes is the result
of plate tectonics. The crust and mantle consists of 30 plates. A
slow movements causes these plates to fold and reshape the crust. It
can cause earthquakes and volcanic eruptions.
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