Download Weathering, Erosion and Soil

WEATHERING, EROSION AND SOIL
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WEATHERING
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MECHANICAL WEATHERING
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Temperature
Freezing temperature causes the expansion of the
molecules of substances - water expands as it freezes
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Cracks in concrete, wood, etc. fills with water. Water freezes
and expands, causing splitting and breaking apart - frost
wedging, ex. pot holes.
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Pressure - factor of mechanical weathering. Bedrock at
great depth are under pressure as over lying rock is
stripped away. The bedrock at depth is exposed. Then the
bedrock can expand and cracks will occur.
Exfoliation - stripping of layers of rock - create a dome
formation, ex. Stone mountain in Georgia
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EXFOLIATION
 Stripping of layers of rock
 Creates a dome formation
 Ex, Stone Mountain in Georgia
 Half Dome Yosemite Valley California
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CHEMICAL WEATHERING
Rocks change composition as the result of
chemical reactions. Agents - H2O,
 O2, CO2, and acids. Temperature tends to speed
up and slow down chemical reactions
 *Rate of chemical Rx (reactions) doubles with
each 10°C increase
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CHEMICAL WEATHERING
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WATER
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Universal solvent,
hydrolysis - reaction of H2O and other substances
Oxygen - oxidation
Substance + O2
new substance
Fe (Iron) + O2 (Oxygen)
Fe2O3 (Rust)
Al (Aluminum) + O2
Al2O3 (Aluminum Oxide)
21% of oxygen is in atmosphere
Minerals - result of oxidation, Ex. Pyrite, magnetite
CO2 - produced through respiration
CO2 + H2O
H2CO3 (Carbonic Acid, weak acid form in the
atmosphere
Carbonic acid reacts with calcite forms (limestone caverns)
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ACID PRECIPITATION
Acid Precipitation - Oxidation of sulfur dioxide and nitrogen oxide - that is released
by human activities
SO2
Industrial emissions
NO2
Motor Vehicles
SO2 + O2 + H2O
Sulfuric acid
NO2 + O2 + H2O
Nitric acid
Acid Rain - PH = less than 5.6
Normal Rain - PH = 5.6
Water in lake - 6 to 8 PH
Lower PH kill fish
To reverse acidification
Acid Ca(OH)2 to the area - Calcium Hydroxide
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EFFECTS OF ACID RAIN ON PLANTS
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WHAT EFFECTS THE RATE OF WEATHERING?
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2000 years to weathering/centimeter of limestone
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Climate - major influence on chemical weathering
variables: precipitation
temperature
evaporation
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Interactions of temperature and precipitation has the greatest effect.
Chemical weathering predominates in climate with warm
temperature, abundant rainfall and lush vegetation.
H2O + CO2
H2CO3 (Carbonic acid - accelerates chemical
weathering
Location: Central America, S.E. Asia
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WEATHERING
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Physical Weathering - dominates cool, dry climates where H2O undergoes
repeated freezing and thawing. Extremely cold climates has no chemical
weathering
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Rock Type and Composition - Characteristics of rocks - hardness and
resistance to breakdown is dependent on the type and composition of the
rock.
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Easy - Sedimentary - easy to break
Igneous Metamorphic - hardest
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Mechanical Weathering - breaking rocks in small pieces - increases
surface area
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Topography - flat level area - rocks remain in place and undergo changes
Hilly area - rocks suffer greater erosion through mass movement
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MOVEMENT
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Erosion - movement of material
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Deposition - materials that are dropped in an area after
movement
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Gravity - associated with erosion - pull materials downward
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“Agent of Mass Movement” (landslides, mudflows,
avalanches)
Running water - greatest erosional agent, stronger than
wind, carries more material a greater distance
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GULLY EROSION IN A PASTURE
RUNNING WATER THAT BECOMES DEEP AND
WIDE (3 METERS)
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RILL EROSION- RUNNING WATER IN SMALL
CHANNELS ON SLOPES
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COASTAL DEPOSITION AND EROSION
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Mississippi carries 750 million metric tones of material—
deposited into the Gulf of Mexico - forms the delta.
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Volume of river flow and the action of tides determine
the shape of delta. Ocean currents and tides carve out
cliffs, arches and other features. Sand particles
accumulate on shorelines and form dunes and beaches
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Sand bars - accumulation of sand underwater create a
barrier island - location: lakes, Gulf of Atlantic Coast
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LANDFORM DEPOSITION
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SAND BAR
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AMAZON DELTA
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GLACIAL EROSION
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Glaciers cover 10% of the earth.
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Erosion is large scale and dramatic.
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Landscape features - waterfalls, lakes, Ex.
Great Lakes, finger lakes (New York)
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LEARN ABOUT GLACIERS
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GLACIER NATIONAL PARK
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S00MtABAhRWSIAbQn7w8QF;_ylu=X3oDMTBvMG
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outube.com%2Fwatch%3Fv%3DBMslDdswGB0&tit
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FINGER LAKES NEW YORK
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WIND EROSION
Areas of limited precipitation and high
temperature, Ex. Death Valley
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WIND EROSION
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AFTER THE WINDS SUBSIDE
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FARMING METHODS
Stops erosion, conserve moisture, trap blowing
snow and protect crops  wind barriers ( wind breakers - thick line of
trees)
 Planting methods
 Plowing methods
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COMBINE DIFFERENT CROPS
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PLANTING CROPS PERPENDICULAR ON A HILL
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NO TILL FARMING
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STRIP FARMING
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DUST BOWL PREVENTION
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FORMATION OF SOIL
Development of Soil - Soil looses covering
of broken rock particles and decaying
organic matter called humus. Overlays the
bedrock.
 Result of chemical and mechanical
weathering and also biological activity.
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SOIL
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Soil composition - Soil forms layers. Pieces of rock are broken
off from the parent rock. Soil is located above it’s parent rock.
H2O sinks down carrying minerals and nutrients through the
layer of the soil. Parent rock determines the kinds of minerals,
proportion of mineral in soil. Length of formation time depends
on the type of rock and climate conditions
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Soil profile - vertical segments of soil layers - well developed
soil - distinct layer
3 main horizons: A - organic/humus - gradual to black color
B - poorer developed - rich in clay minerals,
forms hardpan
layers of soil. Red or brown (iron oxide)
C - Directly above bed rock, most weathered
parent material
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SOIL HORIZONS
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TOPOGRAPHY
Affects the thickness of developing soil.
 Sloped areas cause particles, little particles are
washed away. Soil then, is infertile. South facing
slope has more direct sunlight / more
vegetation, thick soil.
 *Valley - soil thick and rich. Vegetation
contributes to the buildup of humus and supplies
acids to promote the weathering process.
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Soil Types - Appearance, rate of formation and
productivity is determined by climate
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SOIL
Soil varies because of different parent rocks
and undergo different climate conditions.
 Types of plants: animals that live there:
topography: length of time the soil has been
forming.
 Soils are classified based on climate
conditions.
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FOUR TYPES OF SOIL
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polar
temperate
desert
tropical
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POLAR SOIL
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TEMPERATE SOIL
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Supports diverse environments, annual rainfall
50-60 cm, grasslands - abundance of humus,
forest - aluminum rich clays
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Western U.S. rainfall less than 50-60 cm,
support grasses and bushes
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TEMPERATE SOIL
SANTA CLARA CA
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DESERT SOIL
Low level precipitation - Less than 25 cm of
rainfall per year  High level of salts - supports limited
vegetation - light in color— composed of salts
and gypsum
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DESERT SOIL
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TROPICAL SOIL- REDDISH IN COLLOR
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COMPARISON OF SOIL PROFILE AND CLIMATE
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PHYSICAL PROPERTIES OF SOIL
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SOIL FERTILITY
Soil Fertility - measure how well a soil can support the growth
of plants.
Factors affect it
1) availability of nutrients and minerals
2) Number of microorganisms present
3) Amount of precipitation
4) Topography
5) Level of acidity
Natural/commercially produce. Fertilizers are added to
replace minerals. Add nitrates, phosphates, and phosphorus
to the soil.
Limestone (pulverized) added to soil to reduce acidity and
influence crop growth
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