Download The Greenhouse Effect on Earth

The Greenhouse Effect on Earth
Earth’s atmosphere is slightly warmer
than what it should be due to direct
solar heating because of a mild case of
greenhouse effect…
• The majority of Earth’s
atmosphere (N2 and O2) are not
good greenhouse gas.
• The small amount of greenhouse
gases (H2O, CO2) traps (absorb
and re-emit) the infrared radiation,
increasing the temperature of the
atmosphere…
Click on image to start animation
Target 2.a
• Analyze how greenhouse gases directly
affect global climate change.
Water On Earth
The condition is just right!
• The combination of 2 factors: Distance to the Sun and the
greenhouse effect, make it possible for water to stay on Earth.
• N2 and O2 are not greenhouse gas.
• Not much CO2 in the atmosphere.
• Variable amount of H2O in the atmosphere…regulated by the
temperature.
Greenhouse Gases
• The primary components of Earth’s atmosphere, N2 and
O2 ,do not have a significant role in setting the surface
temperature of the planet…
• Greenhouse gas are efficient in absorbing infrared
light…
The most important greenhouse gases are:
– H2O – Water vapor.
– CO2 – Carbon Dioxide
– CH4 – methane
Global Warming
There is a gradual increase in
the average temperature of the
Earth’s atmosphere in the last
100 years…It has risen about
1°C since 1900…
• Are human activities
causing global warming?
• What other (non-human)
factors can cause global
warming?
• How does global warming
affect our life?
Just watch the movies…
Earth’s Temperature Variation in
the past 1,100 years
Target- 2.d
• Describe how water’s properties can
create weathering and erosion of sediment
Weathering: Two Types
• Mechanical engineering
• The breakdown of rock into
solid fragments by physical
processes
• Chemical composition of rock
NOT altered
• Chemical weathering
• The decomposition of rocks
and minerals by chemical and
biochemical reactions
Characteristics
• Joints
– A fracture of rock , along
which no appreciable
movement has occurred
– Sheet jointing or exfoliation
– Frost wedging
• Abrasion
– The gradual wearing down
of bedrock by the constant
battering of loose particles
transported by wind, water
or ice
The jointing in these rocks has
exposed new surface area which
has broken and smoothed due to
wind, water and ice.
Weathering
exfoliation and frost wedging
Frost wedging and biomechanical weathering
Chemical weathering
• Dissolution
– The separation of
materials into ions
in a solution by a
solvent, such as
water or acid
– Rainwater acts as
weak solution of
carbonic acid
– Anthropogenic
actions influence
acidity of rainwater
The marble grave marker has been attacked
by acidic rain because of the calcite
composition. The grave marker on the right,
while old, has not been dissolved because of
its granite composition
Chemical weathering:
ion exchange and the chemical breakdown of feldspar
Factors affecting weathering
• Tectonic setting
– Young, rising
mountains weather
relatively rapidly
– Mechanical
weathering most
common
Factors affecting weathering
• Rock composition
– Minerals weather
at different rates
• Calcite weathers
quickly through
dissolution
• Quartz is very
resistant to
chemical and
mechanical
weathering
• Mafic rocks with
ferromagnesian
minerals weather
more easily
Factors affecting weathering
• Rock structure
– Distribution of
joints influence
rate of
weathering
• Relatively close
joints weather
faster
Factors affecting weathering
• Topography
– Weathering
occurs faster on
steeper slopes
• Rockslides
Factors affecting weathering
• Vegetation
– Contribute to
mechanical and
chemical weathering
– Promotes
weathering due to
increased water
retention
– Vegetation removal
increases soil loss
Vegetation can both hold water
And increase weathering. If removed
Rocks may also be vulnerable to abrasion
Factors affecting weathering
• Biologic activity
– Presence of
bacteria can
increase
breakdown of
rock
Factors affecting weathering
• Climate
– Chemical weathering is
more prevalent in
warm, wet tropical
climates
• Mechanical weathering
less important here
– Mechanical weathering
is more prevalent in
cold, relatively dry
regions
• Chemical weathering
occurs slowly here
Note: temperate regions such as
at the center of the chart
undergo both chemical and
mechanical weathering, i.e.
New York area
Products of Weathering
• Clay
– Tiny mineral particles of any kind that have physical
properties like those of the clay minerals
– Clays are hydrous alumino-silicate minerals
Products of Weathering
• Sand
– A sediment made of
relatively coarse mineral
grains
• Soil
– Mixture of minerals with
different grain sizes, along
with some materials of
biologic origin
– Humus
– Partially decayed organic
matter in soil
Erosion and Mass Wasting
Erosion is the removal of weathering products from
the source and most often occurs by water
• Erosion
– The wearing away of bedrock and transport of loosened
particles by a fluid, such as water
– Example: Sediment moved along the bottom of a
stream
Erosion and Mass Wasting
• Erosion by wind
Particles of sand are transported close to the surface.
finer particles of silt and clay can be transported great
distances
• Erosion by ice
– Glacier
• A semi-permanent or perenially frozen body of ice, consisting
of recrystallized snow, that moves under the pull of gravity
Wind-blown fine sediments
such as this dust cloud can
Be transported across ocea
Erosion and Mass Wasting
Left: deposits of unsorted glacial till from glacier
Right: rock polished and striated by glacier
Erosion by ice:
glacier removes, breaks and transports rock pieces
glaciers scour valleys and deposit piles of debris as
moraines
Erosion and Mass Wasting
• Mass wasting
– The downslope movement of regolith and/or bedrock masses due
to the pull of gravity
• Slope failure
– Falling, slumping or sliding of relatively coherent masses of rock
Erosion and Mass Wasting:
Rock slide, rock fall, and slumping result in downhill transport of broken
rock
Erosion and Mass Wasting
• Flow: If water or air combines with the downward
movement, the regolith can “flow” downhill
• Creep
– The imperceptibly slow downslope flow of regolith
• Unstable slopes move very slowly over long periods of time
Erosion and Mass Wasting
Why do major landslides occur near plate
boundaries?
• Tectonics and mass
wasting
– World’s major
historic landslides
clustered near
converging
lithospheric plates
• High mountains
undergo rapid
weathering
• Earthquakes near
plate
boundaries can
trigger
landslides
This massive slide was triggered by
A magnitude 9 earthquake in Alaska
near a subduction zone.
Critical Thinking
• On Earth, clay minerals are the most
common products of weathering. Samples
from the Moon do not contain any clay
minerals. Why?
• Why are some granite bodies extensively
jointed, while others are essentially joint
free?
Critical Thinking
• On Earth, clay minerals are the most
common products of weathering. Samples
from the Moon do not contain any clay
minerals. Why?
• Why are some granite bodies extensively
jointed, while others are essentially joint
free?