Thursday, Dec. 13th

• Grab a guided notes sheet from the front

table

• Objective: We will describe the history of

the Earth’s atmosphere.

• Warm–up: On guided notes sheet

Atmosphere Activity

Each little block represents 1 in 10,000 or

0.01%.

Atmosphere Activity

Back side, Whole square is 1/100

Each block is 1 ppm

Argon is already

shaded

Composition of Atmosphere

• Nitrogen (78.08%)

• Oxygen (20.94%)

• Argon (0.93 %)

• Trace Gases (0.04%)

– Carbon Dioxide

– Water Vapor

– Neon

– Helium

– Methane…

– Ozone

Composition of Atmosphere

• Non-Variant = Doesn’t change

– Non-Variant Gases: Nitrogen, Oxygen, Argon

• Variant = Changes

– Variant Gases: Ozone, Green House Gases

(Carbon Dioxide, Water Vapor, Methane,

Nitrous Oxide)

Nitrogen, N2

• 78.08%

• Primordial—been part of the atmosphere as

long as there has been an atmosphere.

Oxygen, O2

• 20.94%

• Introduced into atmosphere 2.2 Gya

• Comes from photosynthesis

Argon, Ar

• Ratio of Ar40 to Ar36 tells us the atmosphere

has been outgassed from volcanoes

Water Vapor, H2O

• 0-4% of atmosphere

• Liquid or solid water can be suspended in

clouds and fall as precipitation

• VERY powerful greenhouse gas

• Enters atmosphere through evaporation and

transpiration

Carbon dioxide, CO2

• 390 ppm (0.038%)

• Strong greenhouse gas

• Product of burning fossil fuels

Methane, CH4

• 1.8 ppm (0.00017%)

• VERY strong greenhouse gas

• Farting cows

Nitrous oxide, N2O

• 0.5 ppm (0.00005 %)

• Greenhouse Gas—More impactful than

Carbon Dioxide

• Laughing gas

Ozone, O3

• 0.04 ppm (0.000004%)

• Dangerous in Troposphere

• Small contributor to

Greenhouse Effect

• Shields surface from UV

rays in Stratosphere

The Earth’s Atmosphere

The history of the atmosphere.

How did our atmosphere develop?

Composition of Atmosphere

Today

• Nitrogen (78.08%)

• Oxygen (20.94%)

• Argon (0.93 %)

• Trace Gases (0.04%)

– Carbon Dioxide

– Water Vapor

– Neon

– Helium

– Methane…

– Ozone

The process of forming the Earth was complete by about 4.5 billion

years ago.

Earth experienced a period of

internal melting (due to initial

high temperatures and heat

from radioactive decay).

Dense elements (especially iron and

nickel) sank to the centre of the

Earth, forming the metallic core.

After Earth formation……

Earth’s atmosphere and early life

Initial atmosphere may have had a "primitive"

composition, like that of the sun (gases derived from the

initial nebula).

The modern

atmosphere has a

composition that is very

different from that of

the sun.

Ar40 formed by decay of K40, therefore, was derived from

the Earth after it formed.

E.g., much more Ar40 compared to other isotopes of Ar in

the Earth’s atmosphere.

Other Argon isotopes

were removed with the

early atmosphere and the

Argon40 formed by

subsequent

K40 decay.

Earliest Atmosphere—4.5 billion years ago

• Probably made up primarily of hydrogen

and helium. (The most common gases in the

universe)

• Today’s levels:

– He: 5ppm (0.0005%)

– H2: 0.5ppm (0.00005%)

• Where did it go?

By 4 billion years ago the early atmosphere had the following

composition:

Principle gases:

Carbon dioxide (CO2)

Water vapour (H2O)

Nitrogen(N2)

Minor gases:

Hydrogen (H2)

Hydrogen chloride (HCl)

Sulfur dioxide (SO2)

Note: there was virtually no free oxygen (which makes up about

20% of the modern atmosphere).

Secondary Atmosphere— “Sometime” Later

• Outgassing from cooling magma

– Provided H2O, CO2, SO2, N2, H2, Cl2

Secondary Atmosphere— “Sometime” Later

• Incoming comets burn up in atmosphere

– Releases gases similar to volcanic outgassing

Early Atmosphere Composition

• Mainly Nitrogen

– High amounts of Carbon dioxide, Water, and

Methane

• Very Hot

– GHG

• What’s missing?

Early Atmosphere Composition

• Two main problems:

– No Oxygen for animals to live

– Too much UV radiation for cells to develop

• Reducing Atmosphere

Early Atmosphere Composition

• Reducing Atmosphere

– Reactions decreasing O2 are favored

– 2 Mg(s) + O2(g) 2 MgO(s)

• Oxidizing Atmosphere

– Reactions increasing O2 are favored

– MgO(s) 2 Mg(s) + O2(g)

Early Atmosphere Composition

• How did the atmosphere becoming

oxidizing?

• Or, where did all this Oxygen come from?

1. Photo dissociation of Water

Vapor

• Ultraviolet light broke up water molecules

in the atmosphere

1b. Production of Ozone

• UV light then causes production of ozone

creating a protective shield for life on earth.

2. Anaerobic Bacteria (3.5 bya)

• Anaerobic bacteria: don’t need oxygen

• Turn CO2 into O2

3. Photosynthesis

• Plants use CO2, Water, and Sunlight to

produce O2 and sugar. • CO2 + H2O + sunlight organic compounds + O2

Then and Now • What is the difference between the present

atmosphere and today?

• How was the atmosphere that we know

produced?

Recipes or Comic Strip

• Make either a recipe or comic strip showing

the creation of the Earth’s atmosphere

Comic Strip

Use at least 6 panels

Demonstrate the

compositional changes in the

Earth’s atmosphere

Show the agents responsible

for change

Start with early atmosphere

and end with atmosphere

today

Atmosphere Recipe Create two recipe cards

-One for secondary early

atmosphere

-One for present atmosphere

Provide a description of

atmospheres

Include amounts for “ingredients”

Give instructions for “cooking”—

agents of change

Quick Questions

1. The atmosphere is primarily made up of

what gas?

Quick Questions

2. Where do scientists believe the early

atmosphere (secondary) came from?

Quick Questions

3. What is the primary difference between the

early atmosphere (secondary) and the present

atmosphere?

Quick Questions

4. Which of the following would you expect

to most increase the amount of O2 in the

atmosphere?

a. Ultraviolet light shining on water vapor

b. Volcanic outgassing

c. Photosynthesis

d. Incoming comets

Quick Questions

5. What is the difference between an oxidizing

and reducing atmosphere?

CHANGES TODAY

Ozone

UV Absorption by Dioxygen and

Ozone

Ozone Layer

– What is the maximum concentration of ozone in the ozone

layer? • Maximum of absolute conc about 23 km (up to 1013 molecules/mL)

• Maximum of relative conc about 35 km (up to 10 ppm)

• 16 – 35 km (above bkgd

level)

• Stratosphere contains about

90% of all atmospheric ozone

• Total column ozone: ~300 DU

(1 DU = 0.3 cm thick layer at

1 atm)

The Chapman Cycle Oxygen-only Chemistry

“odd-oxygen” species (Ox) are rapidly

interconverted

Ox = O + O3

OhO2

O10-4 - 10 s

O3

60 - 3 min

O2

h

O2

CFCs

• Chlorofluorocarbons (CFCs)

• The breakdown under the effect of UV light to release chlorine radicals (Cl)

• Especially under cold conditions

• The chlorine radicals react with O3 converting it to O2 and more radicals ClO

Video

Ozone Depletion

• If the rate of breakdown is faster than the

rate of formation the ozone layer thins

• This could develop into hole

• An ozone hole was first observed over the

Antarctic in 1985

CFCs

CFCs

• Used as propellants in aerosol spray cans

• Used as refrigerants in fridges, freezers and

air conditioning units

Hole over Antarctica

Hole over Antarctica • Appears from September to early December

• Think-pair-share: Why do you think the hole appears

over Antarctica?

• Why do you think the hole only appears when it is

“spring” in Antartica?

Tuesday, Dec. 18th

• Do Warm-up on the back of Friday’s

Guided Notes (Greenhouse Gas side)

• Warm-up:

1. What wavelength of light do Greenhouse

Gases absorb?

2. What wavelength of light does Ozone absorb?

• After Warm-up, Review last question on

Ozone side.

Green House Gases

Phet Simulation

Greenhouse Gas

• A gas that absorbs and reemits infrared

radiation

• Short-wave light from sun passes by, but

long-wave infrared radiation from Earth is

absorbed and reemitted.

54

GREENHOUSE EFFECT • Greenhouse effect: process by

which carbon dioxide and other gases in the atmosphere absorb infrared radiation from the sun, forming a “heat blanket” around the Earth

• Some sunlight is reflected and other is trapped as heat to warm the Earth

• Enhanced greenhouse effect: caused from an increase of carbon dioxide, methane, and nitrous oxides from human activities into the air which traps more heat and raises the temperatures of the Earth’s surface

Greenhouse Gases

Concentrations

• Carbon dioxide, CO2 (390 ppm)

• Methane, CH4 (1.9 ppm)

• Nitrous oxide, N20 (0.323 ppm)

• Ozone, O3 (0.009 ppm)

• Water vapor, H20 (0-4%, variable)

How much does each contribute

to the greenhouse effect?

• Water, H2O (36-72%)

• Carbon dioxide, CO2 (9-26%)

• Methane, CH4 (4-9%)

• Ozone, O3 (3-7%)

So what is the deal with CO2?

• How does water vapor get in the air?

• Human’s have very limited impact on water

vapor in the atmosphere

How does CO2 get in the

atmosphere?

• The Carbon Cycle!

59

CARBON

• 4TH most abundant element on Earth

• Essential for life- all organic (living) compounds are composed of carbon

• Found in various forms:

- Carbon dioxide (gas)

- Limestone (solid)

- Wood

- Plastic

- Diamonds

- Graphite

- Fossil fuels

60

CARBON CYCLE

• Movement of carbon

between the atmosphere,

oceans, biosphere, and

geosphere

• Divided into two

components:

1. Geological carbon cycle

2. Biological carbon cycle

61

GEOLOGICAL CARBON CYCLE

• Carbonic acid combines with minerals on the earth’s surface forming carbonates (weathering)

• Carbonates erode from the surface into the ocean and settle on the ocean floor

• Sinks into the earth, heats up, and eventually rises up as carbon dioxide into the atmosphere

* OCCURS OVER MILLIONS OF

YEARS

62

GEOLOGICAL CARBON CYCLE • Carbon dioxide diffuses into the

ocean forming bicarbonates or calcium carbonate (used to make shells and other body parts by organisms such as coral and brachiopod shells)

• These organisms die and their shells and body parts become carbonate-rich deposits

• After a long period of time, these deposits become sedimentary rocks, coal, or oil

63

BIOLOGICAL CARBON CYCLE • The movement of carbon through the processes of photosynthesis and cellular

respiration

• Also, the consumption of living matter by other organisms

• The amount of carbon cycled through annually is a 1,000 times greater than the geological carbon cycle component

64

PHOTOSYNTHESIS • Autotrophs take in carbon dioxide, water, and sunlight to

produce sugars and oxygen

• Chemical Formula:

6CO2 + 6H2O + light energy → C6H12O6 + 6 O2

65

CELLULAR RESPIRATION • Carbon dioxide is released back into the atmosphere by breaking down sugar

during cellular respiration

• Chemical Formula:

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

66

RELEASE OF CARBON DIOXIDE

• CO2 is also released

into the atmosphere

by:

1. Decaying dead matter

2. Forest fires

3. Volcanoes

4. Burning of fossil fuels (coal,

oil, gas)

67

68

HUMAN IMPACT

• Since the onset of the industrial revolution,

burning of fossil fuels and deforestation have lead

to increase of atmospheric CO2

• There is strong evidence that supports the idea that

these activities increase the atmosphere’s ability to

hold in heat (greenhouse effect) and is resulting in

a climate change (global warming)

22.6% increase

382 ppm

Northern

Hemisphere

Growing

Season

Quick Questions

1. Ozone helps prevent ultraviolet radiation

(UV) from reaching Earth’s surface by

a. reflecting UV back into space.

b. diffracting UV into the ionosphere.

c. absorbing UV into its molecular structure.

d. converting UV into gamma rays.

Quick Questions

2. CFCs increase the amount of ultraviolet

radiation reaching Earth because they

a. prevent ozone from forming near Earth’s surface.

b. deplete the amount of ozone in the stratosphere.

c. are absorbed into the Sun, where they change

into ultraviolet radiation.

d. form a layer around Earth, acting like a lens

which increases radiation.

Quick Questions

3. The two must abundant greenhouse gases

in Earth’s atmosphere are

a. Water vapor (H2O) and carbon dioxide

(CO2)

b. Carbon dioxide (CO2) and methane (CH4)

c. Ozone (O3) and carbon monoxide (CO)

d. Nitrogen (N2) and oxygen (O2)

Quick Questions

4. How do humans affect the concentration of

green house gases in the atmosphere?

Quick Questions

5. Your friend learns about global warming

and remarks that we should remove all

greenhouse gases in the atmosphere to save

the planet. In one sentence, what would you

say to your friend?

Recipes or Comic Strip

• Make either a recipe or comic strip showing

the creation of the Earth’s atmosphere

Comic Strip

Use at least 6 panels

Demonstrate the

compositional changes in the

Earth’s atmosphere

Show the agents responsible

for change

Start with early atmosphere

and end with atmosphere

today

Atmosphere Recipe Create two recipe cards

-One for secondary early

atmosphere

-One for present atmosphere

Provide a description of

atmospheres

Include amounts for “ingredients”

Give instructions for “cooking”—

agents of change