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Planet Earth
Chapter 2
2.3 explain how the relationship between Earth and Sun is critical to the study of geography
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
The Planets: Neighbors in Space
• The largest objects that orbit the sun
are called planets.
• At least nine planets orbit our sun.
• Some of the planets have one or more
moons.
• 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.
• They are much more gaseous
and less dense than the
terrestrial planets.
• Pluto, the exception among
the planets, is a ball of ice and
rock.
2.1 explain internal and external physical forces that impact Earth
Asteroids, Comets, and Meteoroids
• Smaller objects in the solar system
include asteroids, comets, and
meteoroids.
• Asteroids are small, irregularly
shaped, planet-like objects.
• Comets are made of icy dust particles
and frozen gases. Meteoroids are
pieces of space debris–chunks of rock
and iron.
Getting to Know Earth
• Earth is the largest of the inner planets. Its diameter
at the Equator is larger than the diameter from pole
to pole.
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.
Landforms
• The earth’s landforms–physical
features of particular shape and
elevations–include continents,
mountains, hills, plateaus, valleys, and
plains.
• The part of a continent that extends
underwater is called a continental shelf.
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.