Download What-Makes-Up-Earths-Atmosphere-Study-Guide

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What Makes Up Earth’s Atmosphere?
Study Guide
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The layer of air that surrounds our planet is called the atmosphere. When
compared to the size of Earth, the atmosphere looks like a very thin blanket
surrounding the entire planet. So, we say that the atmosphere is a thin blanket of
air that surrounds Earth.

Our atmosphere formed millions of years ago as gases from erupting volcanoes
collected around the planet. Over time, the gas mixture changed slowly to
become the atmosphere Earth has now.

The atmosphere now is made up of billions and billions of gas particles –
nitrogen, oxygen, water vapor and other gases.

Plants use carbon dioxide during the process of photosynthesis. Plants give off
oxygen as photosynthesis occurs. Carbon dioxide also absorbs heat energy from
the sun and from Earth’s surface. This helps keep the planet warm.

Water vapor can absorb energy, too. The amount of water vapor in the air varies
from place to place. Air over bodies of water usually contains more water vapor
than air over land. High in the air, water vapor condenses to form clouds
(condensation).

All particles of air pressing down on the surface cause air pressure. Air pressure
changes as you go higher in the atmosphere.

At the surface of Earth, air particles are close together. The higher you go in the
atmosphere, the farther apart the air particles are. So the air pressure is less as
you go higher in the atmosphere.
(more on back)
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Atmosphere Layers

Earth’s atmosphere is divided into four layers: troposphere, stratosphere,
mesosphere, and thermosphere.

The layer closest to Earth is the troposphere. We live in the troposphere and
breathe its air. Almost all bad weather happens in this layer of the atmosphere.
In the troposphere, air temperature decreases as you go higher.

The second layer from Earth is the stratosphere. Some airplanes that travel
long distances fly in the stratosphere to be above most bad weather. The
stratosphere contains most of the atmosphere’s ozone, a kind of oxygen. The
ozone protects living things from the sun’s harmful rays. Temperatures in the
stratosphere increase with height.

The third layer from Earth is the mesosphere. In the mesosphere, air
temperature decreases with height. In fact, the mesosphere is the coldest layer
of the atmosphere.

The fourth layer from Earth is the thermosphere. The thermosphere is the
hot, outermost layer of air. In the thermosphere, temperature increases
quickly with height. Temperatures high in the thermosphere can reach
thousands of degrees Celsius.
(Harcourt Science D6-8)