CHAPTER 4
Introducing Earth
LESSON 1
The Earth System
THE EARTH AS A SYSTEM
The Earth system involves a constant flow of matter
through different parts.
The constant flow, or cycling, of matter through the earth
system is driven by energy. Energy is the ability to do
work.
The energy that drives the Earth system has two main
sources: heat from the sun and heat flowing out of Earth as it
cools.
PARTS OF THE EARTH SYSTEM
The Earth contains air, water, land and life. Each of these
forms its own “sphere.”
Atmosphere
Hydrosphere
Geosphere
Biosphere
ATMOSPHERE
The Earth’s outermost layer is a mixture of gasses. Primarily nitrogen (78%),
oxygen (21%), and argon (1%). Trace amounts of carbon dioxide, neon, helium,
methane, krypton, hydrogen, nitrous oxide, xenon, ozone, iodine, and carbon
monoxide. Lower altitudes also have quantities of water vapor.
The atmosphere we have today is very different from the Earth’s early
atmosphere. When the planet first cooled down 4.4 billion years ago, volcanos
spewed out steam, carbon dioxide and ammonia, and it was 100 times as dense as
today’s atmosphere.