1.2
KEY IDEA
The Earth system consists of
four spheres that all affect one
another: the atmosphere,
the geosphere, the hydrosphere,
and the biosphere.
The Earth System’s Four Spheres
Earth is unique in the solar system: It is the only planet currently known to
support life. This capacity is due to the interactions among its four spheres:
the atmosphere, the geosphere, the hydrosphere, and the biosphere.
Energy moves back and forth among the spheres within the Earth system.
Atmosphere
KEY VOCABULARY
• atmosphere
• geosphere
• hydrosphere
• biosphere
Biosphere
CLASSZONE.COM
Observe a visual model of Earth’s
spheres.
Keycode: ES0102
Geosphere
Hydrosphere
THE FOUR SPHERES of the Earth system interact continually, each affecting the others.
The Atmosphere
The gaseous envelope surrounding Earth is the atmosphere. Composed of
a mixture of gases, the atmosphere provides living things with oxygen and
carbon dioxide. Other gases in the atmosphere absorb and alter rays from
the sun, blocking potentially harmful radiation. Changing amounts of
water vapor in the atmosphere result in areas of high or low humidity and
influence the formation of clouds. Varying areas of atmospheric pressure
cause winds. Storms occur when water vapor, air pressure, and
energy interact.
Earth’s atmosphere is unique in the solar system: It is the only
one that contains free oxygen. The moon has no atmosphere. The
atmospheres of planets like Venus and Jupiter are thick and filled
with gases that would be poisonous to most life forms as we know
them. The mix of gases in Earth’s atmosphere supports the life
forms that thrive on Earth’s surface.
THE ATMOSPHERE is a gaseous envelope
surrounding Earth.
8
Unit 1 Investigating Earth