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Unit 2: The Earth System
Atmosphere, Hydrosphere &
Geosphere
Function, Composition and
Structure of the Atmosphere
Functions
• Air we breath, plants use in photosynthesis
• Filters solar energy, blocking much of harmful
UV wavelengths
• Protects us from “space junk”
• Allows for a natural greenhouse effect keeping
earth warm enough for liquid water and life
• Cycles moisture and heat throughout earth in
moving air systems providing weather patterns
and the water cycle
• weathers and shapes earth’s surface, allowing
the rock cycle
Composition of Today’s
Atmosphere
• Variable components:
• Water (0-4%)
• Dust, ozone, pollution
Compare to neighbors
Structure of Atmosphere
– Gas molecules thin
with altitude
– What holds them near
earth’s surface?
Atmosphere blends to Exosphere
Heating the Atmosphere
• Troposphere=heated by terrestrial
radiation
• Stratosphere& Mesosphere=absorption
and re-radiation of shortwave radiation in
the ozone layer
• Thermosphere=absorption and reradiation of shortwave radiation by oxygen
Evolution of the Atmosphere
1. Loss of original atmosphere due to solar
wind
2. Formation of early atmosphere by
outgassing
3. Evolution of atmosphere by interactions
with biosphere, hydrosphere, and
geosphere
4. Today’s atmosphere
5. Human’s effect on today’s atmosphere
Solar wind
• 1 million tons of matter out into space
every second!
• 95% protons or H+ ions, plasma state
Solar wind is different than earth
wind
• Not as dense
• Plasma vs.
gas
Solar Wind wipes early atmosphere
away
• When sun first began to shine, early
atmosphere in inner solar system blown
out past the asteroid belt where it was
cooler
• Only dense materials with very high
melting points able to remain (rocky,
metallic elements)
Outgassing
• Gases from volcanoes
– water vapor (H2O),
– carbon monoxide (CO),
– carbon dioxide (CO2),
– hydrochloric acid (HCl),
– methane (CH4),
– ammonia (NH3),
– nitrogen (N2),
– sulfur gases.
– no free oxygen
• Additions to atmosphere: perhaps from
comets?
Evidence for composition of early
atmosphere
• Today’s volcanic eruptions
• Rocks from early earth history
• Early organisms are anaerobic (cannot survive in
O2)
Banded Iron Formation
• not present in rocks younger than 1.8 - 2.5 billions
of years ago, when oxygen starting becoming more
abundant.
• Alternating layers of magnetite, hematite (iron
oxide) and silica-rich minerals
• Struggle between
oxygen-rich and oxygen-poor
environment
The Oxygen explosion
• The amount of oxygen increased due to
early life forms, such as cyanobacteria that
produce oxygen as a waste product
• Water vapor split by incoming solar
radiation into hydrogen and oxygen,
hydrogen escapes
Role of the Oceans
• Environment for
early life
• Absorption of
carbon dioxide and
other toxic gases
Consequences of Oxygen Build-up
• Development of ozone (O3) layer which
absorbs harmful UV radiation and
eventaully allowed life on land
• End of banded iron formations which only
formed in low O2
• Oxygen breathing organisms evolved
Composition, function,
structure of Hydrosphere
Function & Significance of
Hydrosphere
• Necessary for the evolution and the
abundance of life
• Helps circulate heat
• Absorbs and facilitates the storage of
carbon dioxide allowing earth to develop
and maintain low CO2 levels
Structure and Composition
• All water on earth
recycles between
reservoirs
• Most freshwater is in
the ground, some in
lakes and rivers,
atmosphere
Water Cycle
Water: changes of state
Evolution of the Hydrosphere
1. Outgassing (& perhaps comets) adds
water vapor to atmosphere
2. Saturated atmosphere causes great
rains
3. Great rains cool surface and collect in
massive freshwater ocean
4. Landmasses weather and running water
carries dissolved material (salts) to the
ocean
5. Water cycle, driven by sun, continues to
cycle water today
Great Rains
Ocean getting salty
• Weathering of
rocks
• Undersea
volcanoes and
vents
• Balance of salt, not
getting saltier
Composition, Structure, &
Function of Geosphere
Function & Significance of
Geosphere
• Storage of most of earth’s matter
• Volcanic activity responsible for
atmosphere, climate changes, new crust
• Plate movements causing crust to be
recycled including elements that
accumulate such as carbon and “salt”
• Provides varied topography on which both
dry and wet land creatures dwell
• Weathers to form soil from which land
plants derive many nutrients
Evolution of Geosphere
1. Solid rock, metal and ice accrete to form
protoplanet from solar nebula
2. Gravitational compression & impacts cause
early earth to become molten
3. Differentiation based on density formed layers
out of molten earth, gasses escaped.
4. Great collision causes large chunk of crustal
rock to rip away & form moon. Gravity pulls
both back into molten spheres
Earth’s Layered Structure
Evolution of Geosphere cont.
5. Crust cools but heat from within causes
eruptions of rock and gas to continue,
also causes plates to shift
6. Plate collisions and volcanic activity
create landmasses above sea level
7. Heat within drives plate motions causing
landmasses to shift and rocks to recycle
8. Interaction between weathering and uplift
create today’s landscape
Plate Tectonics
Rock Cycle
What is the geopshere made
of?
• Common
elements
• Elements
make up
minerals
• Rocks are
made of
minerals
3 main types of rocks
•
•
•
•
•
Based on formation
Igneous=
Sedimentary=
Metamorphic=
Common
characteristics of
each
Rodinia
Gondwana
Brr…
Oceans begin to close
Pangea is forming, Appalachians
Greatest extinction (99%) of all
time!
Pangea breaks up
Major Extinction
Himalayas form
Most recent Ice age
Today
• http://www.ucmp.berkeley.edu/help/timefor
m.html Great site to get overview of events
in each time period and dates
• http://www.scotese.com/earth.htm (good
for geology and climate)
• http://www.pbs.org/wgbh/nova/ice/chill.htm
l ice ages