Weathering

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• Unit 4
• Weathering
• Erosion
• Deposition

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• Weathering
• -the breakdown of rock
• Erosion
• -the moving of sediment
• Deposition
• -when sediments are dropped

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• Weathering
• two types
• Physical weathering
• -when rocks are broken down into smaller pieces
  (sediments), but do not change chemically
• types of physical weathering

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• types of physical weathering
• a) frost action
• -water expands when freezing. When this
  happens in the crack of a rock, freezing water
  splits the rock apart.
• -this is the best example of physical
  weathering
• -occurs in humid (moist) climates of
  temperatures that rise above and below freezing
  

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• types of physical weathering
• b) abrasion
• -when two rocks crash into each other and
  break apart
• -sand crashes into a big rock wearing it down

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• types of physical weathering
• c) root action
• -plant and tree roots break apart rocks

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• Weathering
• two types
• Chemical weathering
• -when rocks are changed chemically into a new
  substance

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• Examples of chemical weathering
• -oxidation when oxygen in the air combines with
  the minerals in rock to form oxides (for example,
  iron and oxygen form iron oxide, rust)

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• Examples of chemical weathering
• -oxidation when oxygen in the air combines with
  the minerals in rock to form oxides (for example,
  iron and oxygen form iron oxide, rust)
• -carbonation occurs when water containing
  carbonic acid dissolves minerals in rock
  (limestone is dissolved by this acid resulting in
  sink holes and caves)

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• Examples of chemical weathering
• -oxidation when oxygen in the air combines with
  the minerals in rock to form oxides (for example,
  iron and oxygen form iron oxide, rust)
• -carbonation occurs when water containing
  carbonic acid dissolves minerals in rock
  (limestone is dissolved by this acid resulting in
  sink holes and caves)

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• Examples of chemical weathering
• -hydration when minerals absorb water, weaken,
  and crumble to form clay

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• Weathering rate is affected by
• 1) surface area of sediment
• 2) climate
• 3) mineral content of sediment

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• 1) Surface area exposed affects weathering

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• Surface area exposed affects weathering
• 1) The more surface area a rock has exposed,
  the faster the weathering rate

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• 2) Climate affects weathering
• climate average long-term weather

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• Climate affects weathering
• -in warm and humid climates, chemical weathering
  is dominant

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• Climate affects weathering
• -in warm and humid climates, chemical weathering
  is dominant
• -in cold and humid climates, physical weathering
  is more dominant

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• Climate affects weathering
• -in warm and humid climates, chemical weathering
  is dominant
• -in cold and humid climates, physical weathering
  is more dominant
• -the more moisture available, the more
  weathering occurs

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Mean annual precipitation (centimeters)
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• 3) Mineral content affects weathering
• the harder the minerals, the more resistant to
  weathering.
• the softer the minerals, the faster the
  weathering

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• How is soil formed?
• Soil is made of
• 1) crushed rocks (sediment)
• 2) organic (living) material, called humus
• Soil is formed by
• 1) weathering
• 2) biological (living) activity

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• How is soil formed?
• Soil layers (called horizons)

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• How is soil formed?
• Soil layers (called horizons)
• A-horizon (topsoil) contains mostly living
  material with some crushed rocks
• B-horizon (subsoil) contains mostly crushed
  rocks with little living material
• C-horizon contains partly weathered rock
• Solid bedrock (unweathered rock)

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Dirt Activities

• http//harcourtschool.com/activity/dirt/index.html
  

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• How is soil formed?
• Soil can be transported or residual.
• Transported soil was moved to a location by an
  agent of erosion, therefore has a different
  composition than the local bedrock
• Residual soil formed at its present location,
  therefore has the same composition as the local
  bedrock.

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• Erosion
• -the moving of sediment
• What moves sediment?
• There are five major AGENTS of erosion
• 1) GRAVITY
• -the force that causes most erosion
• 2) water
• 3) wind
• 4) ice (glaciers)
• 5) humans

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• Agents of erosion
• Water
• a) the faster a river flows, the larger the
  sediment it will carry
• b) as a river carries sediment, the sediment
  becomes more smooth and round

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• Streams
• -the steeper the slope of stream, the greater
  the velocity (speed) of the water
• -the greater the discharge, the greater the
  velocity of water in a stream
• discharge the amount (volume) of water in a
  stream

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Stream velocity
Stream velocity
Stream velocity
particle size carried
discharge
slope
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• Streams
• meanders - curves

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A
E
B
F
C
D
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C
A
D
B
C
D
B
A
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Meander cutoff animation

• http//highered.mcgraw-hill.com/sites/0072402466/s
  tudent_view0/chapter10/animations_and_movies.html
  

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• Streams
• carry sediment three ways
• 1) in solution (dissolved salt)
• 2) in suspension (floating in the middle)
• 3) rolling/bouncing/dragging along the bottom

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Modes of sediment transport animation

• http//highered.mcgraw-hill.com/sites/0072402466/s
  tudent_view0/chapter10/animations_and_movies.html
  

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• Ocean waves
• -are caused by wind
• -the size of the wave is determined by the wind
  speed and the length of time its been blowing
• fetch- the distance wind blows in a straight
  line across water

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• Ocean waves

wavelength
crest
wave height
trough
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• Ocean waves
• terms
• surf-foaming water where a wave breaks

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• Ocean waves
• terms
• surf-foaming water where a wave breaks
• longshore current-ocean current that moves
  sediment parallel to the coastline
• groins/jetties-barriers built to prevent erosion
  of beach sand

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• Agents of erosion
• 2) Wind
• -sediments moved by wind are pitted or frosted
  as a result of abrasion during their travel

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• Agents of erosion
• ice
• glaciers-rivers of ice that flow on land

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• Agents of erosion
• ice
• glaciers-rivers of ice that flow on land
• -sediment that was moved by a glacier has
  parallel scratch marks, called striations.

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• Agents of erosion
• 4) humans
• move sediment by
• -blasting
• -digging
• -cutting down trees
• -forest fires
• -mining

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Three Rivers Implosion

• http//www.dep.state.pa.us/dep/deputate/minres/pow
  erpoint/3-Rivers20Implosion_files/3-RiversImplosi
  on.htm

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• Agents of erosion
• 5) gravity
• -causes water and ice to flow downhill
• -causes mass movement or
• mass wasting (landslides)

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• Deposition
• -the dropping of sediment by an agent of erosion
• Factors affecting deposition
• 1) size
• 2) shape
• 3) density

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Larger sediment settles faster than smaller
sediment
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rounder sediment settles faster than angular
sediment
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More dense sediment settles faster than less
dense sediment
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• Graded bedding

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• Horizontal sorting
• Sorted sediments sediments in size order

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• Colloids very small particles that take very
  long to settle

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Unit 4LANDSCAPES
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• Landscapes-
• -the shape of the land
• -boundaries are well-defined
• Three types of landscapes
• Mountains
• -high areas with distorted structure
• -also called highlands

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• Three types of landscapes
• 2) Plateaus
• -high areas with horizontal structure
• -also called uplands

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• Three types of landscapes
• 3) plains
• -low, flat areas
• -also called lowlands

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• Name the landscape type!

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• Two forces affect landscapes
• 1) uplifting (increases elevation)
• 2) leveling (erosion-decreases elevation)
• If uplifting is dominant, the elevation will rise
  (ex Himalayas)
• If leveling is dominant, the elevation will
  decrease (ex Appalachians)

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• Climate also affect landscapes
• humid (wet) climate-rounded landscape
• arid (dry) climate angular landscape

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• Rivers and glacial landscapes
• river valley- V shape
• glacial valley U shape

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• Is it a river valley or a glacial valley?

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• River drainage patterns
• dendritic-most common pattern-occurs on gentle
  slopes
• radial occurs on mountains

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• River drainage patterns
• annular-occurs on domed mountains
• trellis occurs on parallel folds and faults