The document summarizes the composition and structure of Earth's atmosphere. It is composed primarily of nitrogen (78%) and oxygen (21%), as well as smaller amounts of other gases like carbon dioxide, water vapor, and ozone. The atmosphere does not have a clear upper boundary and becomes less dense with increasing altitude due to decreasing air pressure. It can be divided into layers based on changes in temperature, density, and other factors. These layers include the troposphere, stratosphere, mesosphere, and thermosphere.

1. The Earth’s Atmosphere Composition Structure

2. thin layer of gases enveloping Earth no well-defined upper boundary – just fewer and fewer atoms density decreases with altitude because number of atoms decrease What is the Atmosphere? View of the atmosphere from the space shuttle

3. Air Pressure atmosphere – exerts pressure the pressure is from the mass of the atoms gravity – compresses air near surface (increase density) felt by any surface in contact with air sea level pressure = 15 lb/in 2

4. Composition of Atmosphere atmosphere is a mixture of gases, solid particles, water droplets Small changes are always happening physical processes (volcanoes), biological (plants and animals – transpiration and respiration),

5. major gases: N 2 and O 2 lesser amounts of noble gases (Ar, Ne, Kr, Xe) plus Hydrogen (H) and Helium (He) N 2 : 78% volume O 2 : 21% volume Permanent Gases

6. Water vapor (H 2 0) Carbon Dioxide (CO 2 ) Ozone (O 3 ) Variable Gases

7. source of this gas: evaporation from Earth’s surface water cycle – moves water between oceans, land and atmosphere 75% Earth’s surface covered by some form of water ground water extremely important: clouds, absorb energy Water Vapor This satellite image shows the relative amounts of water vapor: Dark – low water, white – high water vapor

8. sources: respiration, organic decay, volcanoes, natural and man-made caused fires important Greenhouse gas More Carbon dioxide means more heating of the Earth Carbon Dioxide (CO 2 ) Very emotional issue for Americans - Are we having a bad effect on the atmosphere of the Earth???

9. Ozone (O 3 ) consists of 3 O atoms (O 2 + O = O 3 ) highest concentration in stratosphere shields surface from UV radiation UV radiation splits O 3 molecule also contributor to smog  effects people and vegetation

10. Solids and liquids in the atmosphere small solid particles and liquid droplets associated with human and natural processes larger particulate matter – dust, volcanoes, sea spray and combustion major component of urban smog

11. Vertical Structure of the Atmosphere no clearly defined upper boundary density decreases with elevation We divide the atmosphere into layers based on: Changes in temperature

12. Density Gravity pulls the atmosphere downward atmosphere made up of gases which can be compressed lower atmosphere greater density

13. Temperature Layers from Earth’s surface Troposphere Stratosphere Mesosphere Thermosphere Not shown here – The Exosphere! Let’s learn a little about each layer!

14. lowest layer; temperature decreases with altitude thinnest layer (8-16 km, avg. 11 km) where weather occurs primarily heated by Earth’s surface Troposphere

15. Troposphere – when a cloud reaches the top of this layer, they cannot go higher so they flatten out.

16. Stratosphere found above the troposphere temperature rises with elevation Ozone Layer located here upper stratosphere temperature increases with altitude due to absorption of UV (ultraviolet) radiation in the ozone layer Without the ozone layer protecting us, we could not live on the surface of the Earth!

17. Mesosphere above the stratosphere temperature decreases with altitude Meteorites and space dust burns up in this layer

18. Thermosphere above the mesosphere temperature increases with altitude contains a special part called the ionosphere

19. Ionosphere Quartz Lake State Park, Alaska (Curtis, 1996) defined based on electrical characteristics within the thermosphere absorbs cosmic rays, gamma rays, X-rays, some UV rays contains ions: charged electrical particles visible light is emitted when ions are bombarded by cosmic radiation  produce aurora borealis, aurora australis