1. EARTH’S ATMOSPHERE
(AIR)

2. T/F
Air is empty space.
Earth’s atmosphere is important to living organisms.
All the energy from the Sun reaches Earth’s surface.
Earth emits energy back into atmosphere.
Uneven heating in different parts of the atmoshphere creates air circulation patterns.
Warm air sinks, and cold air rises.
If no humans lived on Earth, there would be no air pollution.
Pollution levels in the air are not measured or monitored.

3. HISTORY OF ATMOSPHERE EARLIEST - Primarily hydrogen.
SECOND - Mostly nitrogen plus carbon dioxide and inert gases (volcanoes and constant asteroid impact)
THIRD – Carbon dioxide then used for...

4. OXYGEN!
CYANOBACTERIA
PHOTOSYNTHESIS!

5. What is AIR?
The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earth's gravity.
The atmosphere of Earth protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

6. COMPOSITION OF OUR AIR
By volume, dry air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.
Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere.

7. LAYERS?
The atmosphere has a mass of about 5.15×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface.
The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space.
Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.

8. THE EARTH’S ATMOSPHERE: Atmospheric Layers
EXOSPHERE

9. Troposphere
Most of the air that makes up the atmosphere is found in the troposphere.
The troposphere is the lowest layer of the atmosphere that lies next to the Earth’s surface.
It extends to about 14 kilometers (around 9 miles) above the Earth
Virtually all weather takes place in the troposphere.

10. Troposphere
As you move up into the troposphere the temperature decreases.
At the top of this layer the air temperature is about - 60°C (-76° F).

11. Stratosphere
The stratosphere begins at the top of the troposphere (14 km/ miles) and extends to about 50 kilometers (31 miles) above the surface of the Earth.

12. Stratosphere
As you move up into the stratosphere the air temperature actually increases.
This occurs because of ozone.
Ozone is a gas that absorbs solar radiation and releases it as heat.
The stratospheric or "good" ozone protects life on Earth from the sun's harmful ultraviolet (UV) rays.

13. The ozone layer is located at the bottom of the stratosphere.

14. Mesosphere
The mesosphere begins at about 50 kilometers (31 miles) above the Earth’s surface and extends to 80 kilometers (50 miles).
As you move up into the mesosphere, the air temperature decreases.
Temperatures at the top of this layer can drop to -90°C (- 130°F ).

15. Mesosphere This layer also protects the Earth.
Meteoroids entering Earth’s atmosphere usually burn up in the mesosphere.
The meteors make it through the exosphere and thermosphere without much trouble because those layers don’t have much air. But when they hit the mesosphere, there are enough gases to cause friction and create heat.

16. Thermosphere
The thermosphere is the outermost layer of the Earth’s atmosphere.
It begins at 80 km (50 miles) above the Earth and extends outward into space.
The higher you move in this layer, the higher the temperature.
Temperatures in the thermosphere can reach 1,800°C (3,300°F) (due to the extremely low density of its molecules)

17. Exosphere
The highest layer, is extremely thin and is where the atmosphere merges into outer space.
It is composed of very widely dispersed particles of hydrogen and helium.
The atmosphere does not have a definite edge, and molecules that are part of it can escape the pull of gravity.
Air temp decreases with height.