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Weather and the Atmosphere

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The weather may be hot or cold, wet or dry

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Vocabulary:

weather

The condition of the air around us

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Weather is caused by four factors

1. Temperature2. Moisture3. Air pressure4. Wind

All weather develops in the atmosphere

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Earth is surrounded by a blanket of air called the

atmosphere

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The atmosphere is a mixture of gases

About three-fourths of the atmosphere is nitrogen

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Almost one-fourth is oxygen

The rest of the atmosphere is carbon dioxide and other gases

These gases are important to living things

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People and other animals use oxygen as they breathe

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Plants use carbon dioxide to make food

Living things use nitrogen to make proteins

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The atmosphere is in layers around Earth

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The layer closest to Earth is the troposphere

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Vocabulary:

troposphere

The layer of the atmosphere closest to Earth where nearly

all weather occurs

Nearly all weather occurs in this layer

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The next layer up is the stratosphere

Vocabulary:

stratosphere

The layer of the atmosphere that reaches from the

troposphere to 30 miles above the Earth

The stratosphere contains an important gas called ozone

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Ozone keeps most of the sun’s harmful radiation from

reaching Earth

Farther out are the mesosphere and thermosphere

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Vocabulary:

mesosphere

The layer of the atmosphere beyond the stratosphere

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Vocabulary:

thermosphere

The layer of the atmosphere where the air becomes thin

and fades into space

The air in the thermosphere becomes thinner and thinner

until it fades into space

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