Download Bodies of Salt Water (cont.)

Planet Earth
Places to Locate
• Australia 
• South America 
• Antarctica 
• Africa 
• Europe 
• Mount Everest 
• Asia 
• Dead Sea 
• North America 
• Mariana Trench
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Earth has one moon, which revolves
around the planet about once a month;
in fact, the words moon and month come
from the same Latin word. The relative
positions of the earth, moon, and sun
make the moon appear to be a different
shape every night, from a barely visible
curve to a crescent, a half-circle, an
ellipse, and finally a full circle. The side
of the moon that seems brightly lit is the
side facing the sun
Our Solar System
The sun is at the center of our solar
system. It exerts a strong force of gravity
that keeps Earth and all the other objects
in the solar system revolving around it. 
• At least eight planets orbit our sun. 
• Some of the planets have one or more
moons.
(pages 33–35)
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Our Solar System (cont.)
• Mercury, Venus, Earth, and Mars are
terrestrial planets because they have
solid rocky crusts. 
• Farther from the sun are the gas giant
planets–Jupiter, Saturn, Uranus, and
Neptune. 
(pages 33–35)
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Our Solar System (cont.)
• Asteroids, Comets, and Meteoroids
Smaller objects in the solar system
include asteroids, comets, and
meteoroids. 
• Asteroids are small, irregularly shaped,
planetlike objects. 
• Comets are made of icy dust particles
and frozen gases. Meteoroids are
pieces of space debris–chunks of rock
and iron.
(pages 33–35)
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Getting to Know Earth
• Water, Land, and Air The surface of
the earth is about 30 percent land and
about 70 percent water. 
• The atmosphere is about 78 percent
nitrogen, about 21 percent oxygen, and
about 1 percent other gases, such as
argon.
(pages 35–36)
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Getting to Know Earth (cont.)
(pages 35–36)
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Getting to Know Earth (cont.)
• The part of a continent that extends
underwater is called a continental
shelf.
(pages 35–36)
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Earth’s Heights and Depths
• The highest point on Earth is the
summit of Mount Everest at 29,035
feet (8,852 m) above sea level. 
• Earth’s lowest point of dry land is on
the shore of the Dead Sea at 1,349
feet (411 m) below sea level. 
• The deepest known level of the ocean
floor is the Mariana Trench at 35,827
feet (10,923 m) below sea level.
(page 36)
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Earth’s Heights and Depths (cont.)
In what ways do you think heights
and depths of lands affect the way
that people live?
Possible answers: Heights and depths
affect the way people live because
altitudes affect temperatures, forms of
transportation, clothing, activities,
occupations, and access to shopping,
medical facilities, and schools.
(page 36)
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Critical Thinking
Drawing Conclusions Recently NASA
has launched space probes to explore
Mars. Why might Mars have been chosen
for these explorations?
Mars might have been chosen because it
is close to Earth, is a terrestrial planet like
Earth, and is cooler than other nearby
planets.
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Analyzing Diagrams
Location Study the diagram below.
How is the size of a planet’s orbit
influenced by its distance from the sun?
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In 1906 the booming city of San Francisco
was destroyed by an earthquake that
measured 8.6 on the Richter scale. Over
400 people were killed, and 28,000
buildings were reduced to rubble. Another
slightly less forceful earthquake struck the
city in 1989, doing far less damage and
claiming 67 lives. Most people remember
it because it interrupted the World Series
for 12 days while damages were repaired
in Oakland and San Francisco.
Earth’s Structure (cont.)
• Plate Movement Many scientists
believe that all the continents once were
joined and have broken apart and drifted.
This theory is called continental drift. 
• Plates move gradually. As they move,
they come together and pull apart. 
• This movement pushes up mountains,
creates volcanoes, and produces
earthquakes. 
• These activities are called plate
tectonics.
(pages 37–39)
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Internal Forces of Change (cont.)
• Earthquakes Sudden, violent
movements along the fault lines are
called earthquakes. 
• The Ring of Fire is a zone of
earthquake and volcanic activity
surrounding the Pacific Ocean. 
• Cities in this area, like San Francisco
and Los Angeles, are prone to severe
earthquakes.
(pages 39–41)
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External Forces of Change
• Wind Erosion The movement of
dust, sand, and soil from one place
to another is called wind erosion. 
(pages 42–43)
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External Forces of Change (cont.)
• Water Erosion Rain, rivers, streams,
and oceans wear away soil and rock in
a phenomenon called water erosion. 
• Water erosion often forms valleys and
canyons.
(pages 42–43)
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Analyzing Maps
Region Study the map of plates and
plate movement below. Which plates
are responsible for the earthquakes
that have occurred in California in the
United States?
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The Water Cycle
• The part of the earth that is covered by
water is called the hydrosphere. 
• Most of the hydrosphere is salt water,
found in the oceans, seas, and some
lakes. 
• The rest of the hydrosphere is the
freshwater of lakes, rivers, and springs.
(pages 46–47)
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Bodies of Salt Water
• Oceans About 97 percent of the
hydrosphere is a huge body of salt
water divided into four oceans: the
Atlantic, the Pacific, the Indian, and
the Arctic Oceans.
(pages 47–48)
Bodies of Salt Water (cont.)
• Seas, Gulfs, and Bays Large bodies
of salt water partially enclosed by land
comprise seas, gulfs, and bays. 
• Ocean Water to Drinking Water
Because of the great demand for drinking
water, people are experimenting with
desalination–the removal of salt from
ocean water.
(pages 47–48)
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Bodies of Salt Water (cont.)
(pages 47–48)
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Bodies of Freshwater (cont.)
• Because rivers and streams flow
through land, they carry freshwater
to people and animals. 
• Most people and animals live near
sources of freshwater. 
• Groundwater Groundwater is
freshwater lying beneath the planet’s
surface. 
(pages 48–49)
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Bodies of Freshwater (cont.)
(pages 47–48)
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Analyzing Diagrams
Physical Geography Look at the
diagram of the water cycle below.
What source of water supplies wells
and springs?
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Locating Places
Match the letters on the map with the physical features of Earth.
__1.
B Rocky Mountains
__2.
E Isthmus of Panama
__3.
G Gulf of Mexico
__4.
C Andes
__5.
H Himalaya
__6.
D
__7.
I
__8.
J
__9.
F
__10.
A
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Ural Mountain
Arctic Ocean
Mediterranean Sea
Bay of Bengal
Europe
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