The document describes the composition and layers of Earth's atmosphere. It begins by outlining the learning objectives which are to describe the atmosphere's composition and layers, explain heat transfer mechanisms, and explain the greenhouse effect. It then provides details on the composition of the atmosphere including the main gases, atmospheric dust, and varying components. The layers of the atmosphere are defined based on temperature and composition changes at different altitudes. Heat transfer through radiation, conduction, and convection is explained. Finally, the greenhouse effect is described as gases in the atmosphere trapping heat from the sun like glass in a greenhouse.

2. Learning Objectives
Describe the composition and layers of the Earth’s
atmosphere.
Explain three mechanisms of heat transfer in Earth’s
atmosphere.
Explain the greenhouse effect.

3. The Atmosphere
Atmosphere – the mixture of gases that surrounds the
Earth
The envelope of gases that surrounds the planet.
The atmosphere is made up of a mixture of atoms and
molecules of different kinds.
Contains mostly nitrogen, oxygen, carbon dioxide
These gases are constantly added and removed
Animals and humans breath in and out
Plants produce food
Volcanoes erupt
Cars

5. Composition of the Atmosphere
Nitrogen = 78%
•Volcano eruptions
•Dead plants and
animals decay
Oxygen = 21%
•Plants
Other Gases = 1%
•Argon
•Carbon Dioxide
•Methane
•Water Vapor

6. Composition of the Atmosphere
Atmosphere also contains atmospheric dust
Mainly soil
Salt
Ash from fires
Volcanic ash
Particulate matter from combustion
Skin
Hair
Bits of clothing
Pollen
Bacteria and viruses
aerosols

8. Air Pressure
Earth’s atmosphere is pulled toward Earth’s surface
by gravity
This makes the atmosphere denser near Earth’s
surface
Almost the entire mass of Earth’s atmospheric gases
is located with 30 km of the surface.
The air is less dense at higher altitudes. This makes
breathing more difficult.
A barometer is how you measure air pressure by
mercury, which contains vacuum mercury. The
aneroid barometer which contains vacuum chamber,
lever, spindle and pointer. (video)

9. Mercury Barometer
A mercury barometer is
an accurate and
relatively simple way to
measure changes in
atmospheric pressure.
At sea level, the weight
of the atmosphere
forces mercury 760 mm
(29.9 in) up a
calibrated glass tube.
Higher elevations yield
lower readings because
the atmosphere is less
dense there, and the
thinner air exerts less
pressure on the
mercury.

10. Aneroid Barometer
In an aneroid
barometer, a partially
evacuated metal drum
expands or contracts
in response to
changes in air
pressure. A series of
levers and springs
translates the up and
down movement of
the drum top into the
circular motion of the
pointers along the
aneroid barometer's
face.

11. Mercurial Barometer

12. Aneroid Barometer

14. Layers of the Atmosphere
The atmosphere is divided into four layers based on
temperature changes that occur at different distances
above the Earth’s surface.
Troposphere
Stratosphere
Mesosphere
Thermosphere

16. Without our atmosphere, there would be no life on Earth. A relatively thin envelope,
the atmosphere consists of layers of gases that support life and provide protection
from harmful radiation.

17. The Troposphere
Closest to Earth’s surface
18 km above Earth’s surface
Almost all weather occurs here
Densest atmospheric layer
Temperature decreases as altitude increases

20. The Stratosphere
From 18 km to about 50 km
Temperature rises as altitude increases in
stratosphere
Ozone in the stratosphere absorbs the sun’s
ultraviolet (UV) energy and warms the air
Ozone, O3, is made up of three oxygen atoms
Almost all ozone in the atmosphere is located in the
ozone layer of the stratosphere
Ozone reduces the amount of UV radiation that
reaches Earth.

23. The Mesosphere
From 50 km to 80 km above Earth’s surface
The coldest layer of the atmosphere
Temperatures as low as -93°C.

26. The Thermosphere
The layer farthest from the Earth’s surface
Nitrogen and oxygen absorb solar radiation
The absorption causes atoms to be electrically charged.
These ions radiate energy as light.
Temperatures above 2,000°C
If we could travel here, it would not feel hot to us
Air particles that strike one another transfer heat
The air in the thermosphere is so thin that air particles
rarely collide so they rarely transfer heat.

29. LAYER OF THE ATMOSPHERE BASED
ON COMPOSITION OF GASES
OZONOSPHERE - In this layer ozone concentrations
are about 2 to 8 parts per million, which is much
higher than in the lower atmosphere but still very
small compared to the main components of the
atmosphere.
Ozone layer is located in the lower portion of the
stratosphere from about 15–35 km (9.3–22 mi;
49,000–110,000 ft), though the thickness varies
seasonally and geographically. About 90% of the
ozone in our atmosphere is contained in the
stratosphere.

30. LAYER OF THE ATMOSPHERE BASED
ON COMPOSITION OF GASES
IONOSPHERE - the part of the atmosphere that is
ionized by solar radiation, stretches from 50 to 1,000
km (31 to 620 mi; 160,000 to 3,300,000 ft) and typically
overlaps both the exosphere and the thermosphere.
- It forms the inner edge of the magnetosphere.
- It has practical importance because it influences, for
example, radio propagation on the Earth.
- It is responsible for auroras.

34. LAYER OF THE ATMOSPHERE BASED
ON DISTRIBUTION OF GASES
HOMOSPHERE
HETEROSPHERE

35. HOMOSPHERE
the chemical composition of the atmosphere
does not depend on molecular weight because
the gases are mixed by turbulence.
includes the troposphere, stratosphere, and
mesosphere.
Above the turbopause at about 100 km (62 mi;
330,000 ft) (essentially corresponding to the
mesopause), the composition varies with
altitude.

36. HETEROSPHERE
allows the gases to stratify by molecular weight,
with the heavier ones such as oxygen and
nitrogen present only near the bottom of the
heterosphere.
The upper part of the heterosphere is composed
almost completely of hydrogen, the lightest
element.
This is because the distance that particles can
move without colliding with one another is large
compared with the size of motions that cause
mixing.

38. VIDEOS
Beginning
The divisions of the earth atmosphere
Reveal Earth's Atmosphere

40. Three Types of Heat Transfer
Radiation – Transfer of energy across space
Conduction – Flow of heat from a warmer object to a
colder object when placed in direct contact
Convection – The transfer of heat by air currents

41. Conduction, Convection, Radiation

42. Heating of the Atmosphere
Solar energy reaches Earth as electromagnetic
radiation.
Electromagnetic radiation includes visible light,
infrared radiation, and ultraviolet light.
Almost half of the solar energy that enters the
atmosphere passes through and reaches Earth’s
surface
The rest is absorbed in the atmosphere by clouds,
gases and dust or it is reflected by the Earth’s surface.

43. Movement of Energy in the
Atmosphere
Weather is caused by air that is constantly moving
upward, downward or sideways
Currents of less dense air, warmed by the Earth’s
surface, rise into the atmosphere.
Currents of denser, cold air sink toward the ground.
As currents of air rise into the atmosphere they cool
off
Eventually, the air current becomes more dense than
the air around it and sinks.
Convection current – Continual process of warm air
rising and cool air sinking. A circular motion.

46. The Greenhouse Effect
A greenhouse is a
building where plants
are grown.
Solar radiation enters
the building and heats
up the inside faster than
heat can escape.

47. Greenhouse Gases
Greenhouse Gases – The gases in our atmosphere that
trap and radiate heat
None of the greenhouse gases have a high
concentration in the Earth’s atmosphere
The most abundant greenhouse gases are
Water vapor (varies because of natural processes)
Carbon dioxide (varies because of industry)
Methane (varies because of industry)
Nitrous oxide

48. The Greenhouse Effect
The gases in Earth’s atmosphere act like the glass in a
greenhouse.
Sunlight penetrates the Earth’s atmosphere and heats the
surface of the Earth.
The Earth’s surface radiates heat back to the atmosphere
where only some of the heat escapes into space.
The rest of the heat is absorbed by the greenhouse gases,
which warms the air.
Heat is then radiated back toward the surface of the
Earth.
Without the greenhouse effect Earth would be too cold to
live.