Overview
This lecture explains the structure, composition, and key features of Earth's atmosphere, focusing on its five main layers and their functions.
Composition of Earth's Atmosphere
- Earth's atmosphere is a protective layer of air or gases surrounding the planet.
- The three major components are nitrogen, oxygen, and argon.
Layers of the Atmosphere
- The atmosphere is divided into five distinct layers based on altitude and characteristics.
Troposphere
- Closest to Earth's surface, extends up to about 12 km.
- Known as the lower atmosphere; weather occurs and air is breathable here.
- Temperature decreases with altitude in this layer.
Stratosphere
- Lies above the troposphere; contains the ozone layer.
- Weather balloons and jets operate here to avoid lower turbulence.
- Temperature increases with altitude but remains below freezing.
Ozone Layer
- A region within the stratosphere absorbing most of the Sun's ultraviolet radiation.
Mesosphere
- Located above the stratosphere with very thin air and distant molecules.
- Coldest atmospheric layer; temperatures can drop to -90°C.
- Meteors burn up in this layer.
Thermosphere
- Extends several hundred kilometers above Earth's surface.
- Temperature increases with height due to solar activity; can reach up to 2000ºC.
- Air is very thin; would feel cold despite high molecular temperatures.
Kármán Line
- Altitude marking the limit where traditional aircraft can no longer fly effectively.
Exosphere
- Outermost layer with very few molecules; particles can escape into space.
- No clear upper boundary; some scientists classify it as part of outer space.
Exobase
- The lower boundary of the exosphere, known as the 'critical altitude.'
- Above the exobase, atmospheric temperature remains nearly constant and barometric laws no longer apply.
Key Terms & Definitions
- Troposphere — Lowest atmospheric layer where weather occurs.
- Stratosphere — Layer above troposphere, contains ozone layer.
- Ozone Layer — Stratospheric region absorbing UV radiation.
- Mesosphere — Middle layer where meteors burn, coldest temperatures.
- Thermosphere — Layer with temperature rising rapidly due to solar activity.
- Kármán line — Boundary marking the limit of traditional aircraft flight.
- Exosphere — Outermost region with escaping atmospheric particles.
- Exobase — Lower boundary of the exosphere where barometric laws cease.
Action Items / Next Steps
- Review the characteristics of each atmospheric layer.
- Study the role and importance of the ozone layer.
- Prepare for quiz on atmospheric composition and layer functions.