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The Atmosphere
Earth Systems
Planets of the Solar System Section 1
Formation of Solid Earth
The diagram below shows the differentiation of Earth.
Planets of the Solar System Section 1
Formation of Solid Earth, continued
Present Solid Earth
• Eventually, Earth’s surface cooled enough for solid rock
to form from less dense elements that were pushed
toward the surface during differentiation.
• Earth’s surface continued to change as a result of heat in
Earth’s interior as well as through impacts and through
interactions with the newly forming atmosphere.
Planets of the Solar System Section 1
Formation of Earth’s Atmosphere
• The atmosphere formed because of differentiation.
• The original atmosphere of Earth consisted primarily of
hydrogen and helium.
Earth’s Early Atmosphere
• Earth’s gravity would have been too weak to hold high
concentrations of hydrogen and helium gases.
• These gases were probably blown away by solar winds.
• Earth’s magnetic field, which protects that atmosphere
from the solar wind, might not have been fully
developed.
Planets of the Solar System Section 1
Formation of Earth’s Atmosphere, continuedOutgassing
• Volcanic eruptions released large amounts of gases, mainly water vapor, carbon dioxide, nitrogen, methane, sulfur dioxide, and ammonia. This process, known as outgassing, formed a new atmosphere.
• The ozone formed from remaining oxygen molecules after solar radiation caused ammonia and some water vapor to break down.
• The ozone collected in a high atmospheric layer around Earth and shielded Earth’s surface from the harmful ultraviolet radiation of the sun.
The Secondary Atmosphere
� Formed from degassing of volcanoes
� Gases emitted probably similar to the gases emitted by volcanoes today.� H2O (water), 50-60%
� CO2 (carbon dioxide), 24%
� SO2 (sulfur dioxide), 13%
� CO (carbon monoxide),
� S2 (sulfur),
� Cl2 (chlorine),
� N2 (nitrogen),
� H2 (hydrogen),
� NH3 (ammonia) and
� CH4 (methane)
Earth’s Present Atmosphere
Nitrogen (N2)-
78%,
Oxygen (O2)-
21%,
Carbon Dioxide (CO2) 0.03 %,
Where did all the oxygen come from?
Volcanic
outgassing
Modern
Atmosphere
H2O – 50-60% N2 – 78%
CO2 – 24% O2– 21%
SO2 – 13% CO2– 0.03%
1. Where did all the O2 come from?
2. Where did all the CO2 go?
Planets of the Solar System Section 1
Formation of Earth’s Atmosphere, continuedEarth’s Present Atmosphere
• Organisms that could survive in Earth’s early atmosphere developed.
• Some of these organisms, such as cyanobacteria and early green plants, used carbon dioxide during photosynthesis.
• These organisms produced oxygen as a byproduct of photosynthesis and helped slowly increase the amount of oxygen in the atmosphere.
Planets of the Solar System Section 1
Reading check, continued
How did green plants contribute to Earth’s present-day
atmosphere?
Green plants release free oxygen as part of
photosynthesis, which caused the concentration of oxygen
gas in the atmosphere to gradually increase.
Planets of the Solar System Section 1
Formation of Earth’s Oceans
• The first ocean was probably made of fresh water.
• Over millions of years, rainwater fell to Earth and
dissolved some of the rocks on land, carrying those
dissolved solids into the oceans.
• As the water cycled back into the atmosphere through
evaporation, some of these chemicals combined to form
salts. Through this process, the oceans have become
increasingly salty.
Planets of the Solar System Section 1
Formation of Earth’s Oceans, continued
The Ocean’s Effects on the Atmosphere
• The oceans affect global temperature by dissolving
carbon dioxide from the atmosphere.
• Scientists think that early oceans also affected Earth’s
early climate by dissolving carbon dioxide.
• Carbon dioxide in the atmosphere keeps energy from
escaping into space and thus helps to heat the
atmosphere.
Origin of the atmosphere
� What happened to Earth’s original atmosphere?
� Earth’s original atmosphere was composed mainly of
Hydrogen and Helium. These are very light elements
and were driven off by the solar wind early in Earth’s
history.
� How did Earth’s secondary atmosphere form?
� Earth’s secondary atmosphere formed from
volcanic outgassing. Volcanic eruptions emit H2O,
CO2, N2, CO, SO2. These heavier gases are held in place
by gravity.
Formation of the oceans
� The earth is cool enough that H2O condenses to form the oceans.� Estimates of the amount of H2O
outgassed is not enough to fill the oceans
� It seems likely that a large volume of water was added by the impact of icy meteors on the atmosphere.
� CO2 dissolves into the oceans.
Life evolves in the Oceans
� Ingredients necessary for life� NH3 – ammonia
� CH4 – Methane
� H2O – Water
� These can produce amino acids, the building blocks of life
� Life may have originated
� under the primitive
atmosphere
� at hydrothermal vents deep
in the oceans
� deep in the earth’s crust
Life changes the atmosphere
� With the evolution of life the first cellular organisms (cyanobacteria) began to use the gasses in the early atmosphere (NH3 –ammonia, CH4 – methane, H2O – water) for energy.
Photosynthetic organisms evolve.
These organisms use CO2 and produce oxygen (O2) as a waste product.
� Where did the O2 come from?
� Produced by photosynthetic life.
� Where did the CO2 go?
� Dissolves in water in the oceans
� Used by life during photosynthesis and buried
when plants and micro-organisms die.
� The source of coal and oil
� Held as CaCO3 in limestone (Rocks)
Early history of life and the
atmosphere
� The Earth is about 4.6 billion years old.
� Life first appears in the oceans at least 3.5 billion years ago.
� 0.9 billion years ago there is enough oxygen in the atmosphere to produce the ozone layer and life can finally move onto land.� The ozone layer protects the earth from harmful ultra
violet radiation from the sun.
The other planets
� Venus � Closer to the sun
� Very hot at the surface so water vapor in the atmosphere does not condense.� Runaway greenhouse effect
(482oC, 900oF).
� No oceans or rainfall so CO2
does not dissolve.
� Has a very dense atmosphere.
The other planets
� Mars
� Further from the sun
� Smaller than Earth
� So small that most of the
atmosphere escaped into
space.
� No oceans or rainfall so CO2
stays in atmosphere.
� 98% of atmosphere is CO2.
• Jupiter
– Huge (318x earth’s mass)
– Kept all its original
atmosphere
– 80% Hydrogen
– 20% Helium
Key Ideas
� Describe the composition of Earth’s
atmosphere.
� Identify the layers of the atmosphere.
� atmosphere a mixture of gases that surrounds a
planet, such as Earth
� The most abundant elements in air are the gases
nitrogen, oxygen, and argon.
� The two most abundant compounds in air are
the gases carbon dioxide, CO2, and water vapor,
H2O.
� In addition to containing gaseous elements and
compounds, the atmosphere commonly carries
various kinds of tiny solid particles, such as dust
and pollen.
Composition of the Atmosphere
Modern atmosphere
Nitrogen (N2)-
78%,
Oxygen (O2)-
21%,
Carbon Dioxide (CO2) 0.03 %,
Atmospheric Composition % by Volume
Major ConstituentsNitrogen (N2) 78.08%Oxygen (O2) 20.94%
Active Minor ConstituentsWater vapor (H2O) variable (0.01% at the poles,
5% at the equatorCarbon Dioxide (CO2) 0.037%Methane (CH4) 0.00015%Nitrous oxide (NO2) 0.00005%Ozone (O3) 0.000007%CFC’s 0.00000014%
Inactive Minor ConstituentsArgon 0.83%Neon 0.0018%Helium 0.00052%Krypton 0.0001 %
Xenon 0.000009%
Matter Cycles play an important role
in the Atmosphere
� Physical and biological processes (matter
cycles) maintain Earth’s atmosphere in a
state of chemical disequilibrium.
� Carbon Cycle – photosynthesis and
respiration
� Nitrogen Cycle
� Water Cycle
� Nitrogen makes up about 78% of Earth’s atmosphere and is maintained through the nitrogen cycle.
� Nitrogen is removed from the air mainly by the action of nitrogen-fixing bacteria.
� The bacteria chemically change nitrogen from the air into nitrogen compounds that are vital to the growth of all plants.
� Decay releases nitrogen back into the atmosphere.
Nitrogen in the Atmosphere
Oxygen in the Atmosphere
� Oxygen makes up about 21% of Earth’s atmosphere.
� Animals, bacteria, and plants remove oxygen from the air as part of their life processes.
� Land and ocean plants produce large quantities of oxygen in a process called photosynthesis.
� The amount of oxygen produced by plants each year is about equal to the amount consumed by all animal life processes.
Water Vapor in the Atmosphere
� As water evaporates from oceans, lakes, streams, and soil, it
enters air as the invisible gas water vapor.
� Plants and animals give off water vapor during transpiration or
respiration. But as water vapor enters the atmosphere, it is
removed by the processes of condensation and precipitation.
� The percentage of water vapor in the atmosphere varies
depending on factors such as time of day, location, and season.
Ozone in the Atmosphere
� ozone a gas molecule that is made up of three
oxygen atoms
� Ozone in the upper atmosphere forms the ozone
layer, which absorbs harmful ultraviolet
radiation from the sun.
� Without the ozone layer, living organisms would
be severely damaged by the sun’s ultraviolet
rays.
� Unfortunately, a number of human activities
damage the ozone layer.
Particulates in the Atmosphere
� The atmosphere contains various tiny solid and liquid particles, called particulates.
� Particulates can be volcanic dust, ash from fires, microscopic organisms, or mineral particles lifted from soil by winds. Pollen from plants and particles from meteors that have vaporized are also particulates.
� Large, heavy particles remain in the atmosphere only briefly, but tiny particles can remain suspended in the atmosphere for months or years.
Layers of the Atmosphere
� Earth’s atmosphere as a distinctive pattern of
temperature changes with increasing altitude.
� The temperature differences mainly result from
how solar energy is absorbed as it moves
through the atmosphere.
� Scientists identify four main layers of the
atmosphere based on these differences.
The Troposphere
� troposphere the lowest layer of the
atmosphere, in which temperature drops at a
constant rate as altitude increases; the part of
the atmosphere where weather conditions exist
� At an average altitude of 12 km, the
temperature stops decreasing. This zone is
called the tropopause and represents the upper
boundary of the troposphere.
The Stratosphere
� stratosphere the layer of the atmosphere that lies between the troposphere and the mesosphere and in which temperature increases as altitude increases; contains the ozone layer
� In the upper stratosphere, the temperature increases as altitude increases because air in the stratosphere is heated from above by absorption of solar radiation by ozone.
� The stratopause, about 50 km above Earth’s surface, marks the upper boundary of the stratosphere.
The Mesosphere
� mesosphere the coldest layer of the
atmosphere, between the stratosphere and the
thermosphere, in which the temperature
decreases as altitude increases
� The mesosphere is located above the
stratopause and extends to an altitude of about
80 km.
� The upper boundary of the mesosphere, called
the mesopause, has an average temperature of
nearly −90°C, which is the coldest temperature in the atmosphere.
The Thermosphere
� thermosphere the uppermost layer of the atmosphere, in which temperature increase as altitude increases; includes the ionosphere
� Temperature increases as altitude increases because nitrogen and oxygen atoms absorb solar radiation.
� The lower region of the thermosphere, at an altitude of 80 to 400 km, is commonly called the ionosphere.
� Interactions between solar radiation and the ionosphere cause the phenomena known as auroras.
The Thermosphere, cont’d
� There are not enough data about temperature
changes in the thermosphere to determine its
upper boundary.
� However, above the ionosphere is the region
where Earth’s atmosphere blends into the
almost complete vacuum of space.
� This zone of indefinite altitude, called the
exosphere, extends for thousands of kilometers
above the ionosphere.
This diagram shows
the different layers
of the atmosphere.
Layers of the Atmosphere,
continued
Reading Check
What is the lower region of the thermosphere
called?
The lower region of the thermosphere is called the
ionosphere.
Sun - our star – the source of most of our energy
1st Law of Thermodynamics
� Energy cannot be created nor destroyed,
but energy can be transformed from one
form to another.
2nd Law of Thermodynamics
� In every energy transformation (from one
form to another) energy tends to degrade
from a concentrated “high quality” or
“useful” form, to a dispersed “low quality”,
“less useful” form.
� When energy is converted between forms
some energy is converted into unusable heat.
� This means that a constant supply of energy is
needed to sustain a system over time.
� Energy in = Energy Out
What are the 3 ways heat can be
transferred?
� Radiation: transfer by
electromagnetic waves.
�
Conduction: transfer by
molecular collisions.
�
Convection: transfer by
circulation of a fluid.
Image from: http://www.uwsp.edu/geo/faculty/ritter/geog101/uwsp_lectures/
Insolation (Incoming Solar Radiation)
� Insolation drives nearly all physical and biological processes on earth.
� Of the solar energy striking the earth’s outer atmosphere
� 30-35% is reflected� Clouds reflect 19-24%� Dust and gas molecules in the atmosphere reflect 6-7%� Earth’s surface reflects 3-4%
� 40-45% is absorbed by the atmosphere (heats atmosphere)
� 20-25% Evaporates water to drive the hydrologic cycle.
� 1% generates wind
� <1% is used by green plants for photosynthesis. (this photosynthesis is the basis for virtually all animal life on earth – except for some very specialized biotic communities around deep sea vents)
Heat Budget
Heat Budget
Energy Balance
Energy Balance: (Energy in = energy out)
� The Earth receives energy from the sun.� In turn biological and physical processes
transform the Insolation into other forms of energy.
� Ultimately the energy flowing through the Earth system is emitted back into space.
� If more energy is received and held than is re-radiated then the balance is upset and the earth will warm.
� In contrast if more energy is re-radiated than is received then earth would cool.
Greenhouse effect vs Global Warming
� Greenhouse effect
� The warming of atmosphere that
occurs when carbon dioxide, water
vapor, and other gases absorb and
re-radiate infra-red radiation
(heat). The natural greenhouse
effect allows the atmosphere to
maintain the temperatures needed
for biological processes.
Global Warming
� A gradual increase in the
average global
temperature that is due to
a higher concentration of
greenhouse gases in the
atmosphere.
GreenHouse Gases
Water Vapor (H2O)
� Natural sources water cycle, evaporation
� Human sources increased evaporation,
spray irrigation
� Present concentration 01% at the poles
5% at equator
� Share of effect 98%
� Residence time ~ 9days
Carbon Dioxide (CO2)
� Natural sources� respiration, decomposition, natural fires
� Human sources� burning of fossil fuels, deforestation
� Present concentration� 383ppm (2007)
� Share of effect� 57% of the share not caused by H2O
� Residence time� 3-7 years (200 years ?)
� Rate of increase� 2% per year
� Carbon sinks� seawater, forests, marine organisms, rocks
Mauna Loa Observatory CO2 Measurements
� CO2 in atmosphere today
~383 ppm (2007)
� Estimated pre-industrial
concentration -= 288
ppm
� Highest past level that
we can measure in ice
cores, ~125,000 years
ago (280-300 ppm!)
Chlorofluorocarbons (CFC’s)
� Natural sources NONE – they are synthetic chemicals
� Human sources coolants in air conditioners, freezers,
refrigerators, solvents, foaming
agents, aerosol propellants.
� Present concentration - 2970 ppt(v) 1990
� Share of effect 25% of the 2% not caused by H2O
� Residence time 65-130 years
� Rate of increase ? <5% per year and decreasing
� Potency 1500–7000 times more potent than CO2
� Sinks eventual stratospheric reactions
Methane (CH4)� Natural sources anaerobic bacteria in
wetlands, termites, natural gas escaping from deposits, biomass burning
� Human sources rice paddies, landfills, cattle, oil and gas extraction
� Present concentration 1.7 ppb (v) 1991
� Share of effect 12% of the 2% not caused by H2O
� Residence time 7-11 years
� Rate of increase 1% per year
� Potency 25 times more potent than CO2
Nitrous Oxide (N2O)� Natural sources Forest Fires, grassland fires,
microbes, animal wastes
� Human sources Fertilizer manufacture and use, livestock wastes, fossil fuel burning, biomass burning, nylon production, nitrate contaminated groundwater.
� Present concentration 308 ppb(v) 1990
� Share of effect 6% of part not caused by H2O
� Residence time 150-190 years
� Rate of increase .25% per year
� Potency 230 times more potent than CO2
Notes: residence time is in the atmosphere. CFC’s and N2O are also responsible for Ozone depletion in the atmosphere.
Source: Environmental Notebook, 2001, Fred Montague
� Notes: residence time is in the atmosphere.
CFC’s and N2O are also responsible for Ozone
depletion in the atmosphere.
� Source: Environmental Notebook, 2001, Fred
Montague
Assessment: Answer each of the following questions in a paragraph of 3-5 complete sentences
1. Describe the composition of the Atmosphere.
2. Describe the formation of Earth’s present atmosphere.
3. Explain the three mechanisms of heat transfer in Earth’s Atmosphere.
4. Describe the flow of energy in the atmosphere.
5. Describe the role of Greenhouse gases in Earth’s Atmosphere.
6. How does human activity change some greenhouse gas levels?
7. Describe the role of Ozone in the stratosphere.