Page 110 - Science Course 1 (Book 2)

Mo9-L3b: What Makes Up the Earth’s Atmosphere?

Key Concept SUMMARY
What is the Origin of Earth’s Atmosphere?
What is the Origin of Earth’s Atmosphere?
The atmosphere is a thin layer of gases
How did Earth’s present atmosphere form? surrounding Earth.

Acids in the air are formed when sulfur dioxide and
What Makes Up the Earth’s
Mo9-L3b nitrous oxide combine with water vapor.
Atmosphere?
KEY CONCEPTS:
1.What is Earth’s atmosphere made of?

Let’s Begin

Composition of the Atmosphere

Today’s atmosphere is mostly made up of invisible
gases, including nitrogen, oxygen, and carbon dioxide.
About 78 percent of the atmosphere is nitrogen, and Many tiny solid particles, such as pollen, dust, and salt, can
about 21 percent is oxygen. enter the atmosphere through natural
processes.
The amounts of water vapor, carbon dioxide, and
ozone vary. Solid particles of ash from volcanic eruptions and exhaust
sooth from cars are also present in the atmosphere.

One way solid
particles enter the
atmosphere is from
volcanic eruptions.

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