Earth's Atmosphere and Its Layers

• The atmosphere is a layer of gases around a planet, held by gravity.
• Earth's atmosphere primarily consists of nitrogen, oxygen, and argon.
• The atmosphere extends approximately 300 miles from the Earth's surface.

Atmospheric Layers

• The atmosphere is divided into five layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
• Troposphere:
  • The lowest layer, from the surface to 7.5 miles.
  • It is the home to humans, animals, and plants.
  • It is the densest layer.
  • It is where weather occurs and contains 99% of the atmosphere's water vapor.
• Stratosphere:
  • Located above the troposphere, extending from 7.5 to 31 miles.
  • Contains the ozone layer.
  • Commercial jets fly here to avoid weather turbulence.
• Mesosphere:
  • Extends from 31 to 50 miles.
  • It is a cold layer where meteors burn up.
  • Can be reached by small rockets and rocket-powered aircraft.
• Thermosphere:
  • Ranges from 50 to 440 miles.
  • Features very low density, and is free of clouds and water vapor.
  • The International Space Station orbits within this layer.
• Exosphere:
  • Extends from 440 to 6,200 miles.
  • The atmosphere merges with outer space.
  • Particles are of very low density and often lost to space due to solar wind.
  • Most of Earth's satellites orbit here.
• The atmosphere is generally defined as the first 62 miles (100 kilometers) of gases.

Atmospheric Gas Composition

• Nitrogen (N2) accounts for approximately 78.08%.
• Oxygen (O2) accounts for approximately 20.95%.
• Water (H2O) accounts for approximately 0.4%.
• Argon (Ar) accounts for approximately 0.93%.
• Carbon Dioxide (CO2) accounts for approximately 0.04%.
• Neon (Ne) accounts for approximately 0.002%.
• Helium (He) accounts for approximately 0.0005%.
• Methane (CH4) accounts for approximately 0.0002%.
• Hydrogen (H2) accounts for approximately 0.00005%.
• Nitrous Oxide (N2O) accounts for approximately 0.00003%.
• Ozone (O3) accounts for approximately 0.000004%.

Importance of Gases

• The atmosphere supports life through respiration and photosynthesis.
• Most important benefits are the ozone layer and the greenhouse effect.

The Ozone Layer

• Located in the stratosphere.
• Ozone consists of three oxygen atoms (O3)
• It absorbs ultraviolet light
• It prevents most UV light from reaching Earth's surface, protecting life from its harmful effects.
• Damage to the ozone layer was caused by chemicals like chlorofluorocarbons (CFCs).
• The Montreal Protocol in 1987 banned these chemicals.
• The ozone layer has been recovering since these bans.

The Greenhouse Effect

• Without the greenhouse effect, Earth would be about 59°F colder.
• Greenhouse gases trap infrared light, warming the Earth.
• Key greenhouse gases include carbon dioxide, methane, and water vapor.
• Human activities have increased carbon dioxide levels through burning fossil fuels.
• This has led to global warming (climate change), causing an artificial increase in Earth's average temperature.

Explore Earth's atmosphere, a layer of gases held by gravity, composed mainly of nitrogen, oxygen, and argon. Discover its five layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Each layer has unique characteristics such as weather patterns, ozone presence, and temperature variations.