2. Atmosphere – importance and structure. Air composition.

What are the layers of Earth's atmosphere?

Troposphere, Stratosphere, Mesosphere, Thermosphere, Exosphere, Magnetosphere

Mnemonic: The Silly Monkeys Twirled Endlessly

Where do three-quarters of the atmosphere lie?

Within the troposphere

Where is the ozone layer located and what is its function?

In the stratosphere; absorbs ultraviolet radiation

What is the Karman line?

Boundary between Earth’s atmosphere and outer space

• (100 km, thermosphere)

How far can the exosphere extend?

From 500 km to 10,000 km

What is the atmosphere and its function?

A gas layer surrounding Earth; protects life via UV absorption, heat retention, and temperature regulation

ow much atmospheric air does the troposphere contain?

80%

What is the depth of the troposphere?

17 km at the equator, 7 km at the poles

What are key features of the troposphere?

• Wettest layer,

• warmest near surface,

• temp

• pressure decrease with altitude

What is temperature inversion?

When warm air sits over cooler air, trapping it; stable condition

What is the tropopause?

Boundary between troposphere and stratosphere

Highlights of the stratosphere?

• Temp increases with altitude,

• contains ozone layer,

• aircraft fly here

What is the extension of the mesosphere?

50 to 85 km

Highlights of the mesosphere?

Extremely cold (-90°C), low density and pressure, temp decreases with altitude

High-altitude clouds in the mesosphere?

Noctilucent clouds, polar mesospheric clouds

Boundary between mesosphere and thermosphere?

Mesopause

What would happen to a person in the mesosphere?

UV burns and blood boiling due to low pressure

What is the thickest layer of the atmosphere?

Thermosphere

Extension of thermosphere?

80 km to 550 km

Highlights of the thermosphere?

Contains ionosphere and exosphere; ISS orbits here; auroras occur

What happens in the ionosphere?

Solar radiation ionizes gas molecules → auroras

What is the exosphere?

Outermost layer of the thermosphere

What is the exobase?

Lower boundary of the exosphere

Why is there no exopause?

Because the exosphere gradually fades into space

Boundary between exosphere and thermosphere?

Thermopause

Highlights of the exosphere?

Very low density, contains satellites, fades into space

Why does warm air rise?

Warm air is less dense and more buoyant → rises via convection

What is a temperature gradient?

Change in temperature with altitude

Composition of atmospheric air?

• N₂ – 78.1%,

• O₂ – 20.9%,

• CO₂ – 0.03-0.4%,

• other gases – ~1%

Difference between air and atmosphere?

• Air is what we breathe;

• atmosphere contains air, vapor, dust, seeds

Oxygen content in atmospheric air?

20.9%

At what oxygen concentration do symptoms begin?

17 vol% → fatigue, discomfort

At what oxygen level does death occur?

8 vol%

At what altitude is the critical oxygen level reached?

8 km

Nitrogen concentration and function?

78.1%; no direct function, dilutes oxygen

Carbon dioxide concentration and effect?

0.03-0.04%; increases in exhaled air

What CO₂ level causes breathing difficulty?

2 vol%

Name the other gases in the atmosphere.

Argon, neon, radon; all make up ~1%