Earth's Atmosphere

Layers of the atmosphere, weather and climate

Earth's Atmosphere

The atmosphere is the layer of gases surrounding Earth. It is made mostly of nitrogen (78%) and oxygen (21%), with small amounts of argon, carbon dioxide and other gases. The atmosphere protects us from harmful radiation and keeps the planet warm.

Layers of the Atmosphere

From lowest to highest: • Troposphere (0–12 km) — where weather happens and we live • Stratosphere (12–50 km) — contains the ozone layer • Mesosphere (50–80 km) — where meteors burn up • Thermosphere (80–700 km) — very hot, where the ISS orbits • Exosphere (700+ km) — thins into space

Example

Weather vs Climate

Weather is the day-to-day condition of the atmosphere (e.g. sunny, rainy, 25°C today in Durban). Climate is the average weather over a long period (e.g. KwaZulu-Natal has a subtropical climate — warm and humid). South Africa has diverse climates: Mediterranean (Western Cape), semi-arid (Northern Cape), subtropical (KZN).

Note

Human Impact

Burning fossil fuels releases carbon dioxide, which increases the greenhouse effect and contributes to global warming. The ozone layer in the stratosphere protects us from UV radiation — damage to it increases the risk of skin cancer.

Key Vocabulary

AtmosphereThe layer of gases surrounding Earth

TroposphereThe lowest layer of the atmosphere where weather occurs

Ozone layerA layer in the stratosphere that absorbs UV radiation

WeatherThe state of the atmosphere at a specific time and place

ClimateThe average weather conditions in a region over many years

Greenhouse effectThe trapping of heat in the atmosphere by gases like CO₂

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Atmosphere

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