Download Unit 4 Notes

Unit 4: Weathering, Erosion, and
Deposition
(Text ch.5, 6, and 7)
(Review Book p.130-168)
I Weathering: the breakdown of
rocks into sediments by exposure to
air and water.
(see text p.126)
vidclip- Weathering intro.
A. Physical (or Mechanical) Weathering:
changes the shape or size of a rock.
(How nature smashes rocks)
1. Frost Action (Wedging):
 During the day, liquid water
seeps into cracks in the rock.
 At night, water freezes and
expands, breaking rock apart.
(see text p.127)
[Diagram]
frost wedging animation
Observe the effects of mechanical weathering.
2. Plant Roots grow into cracks,
breaking rock apart. (see text p.128)
plant action animation
Observe the effects of mechanical weathering.
3. Abrasion: sediments are
transported by water,or wind. They
wear away by bumping and grinding
together.
[diagram]
stream abraded rocks
YouTube - Bill Nye the Science Guy - Pet Rock Theatre
4. Exfoliation: occurs when heavy
pressure is removed from
underlying rocks.
(see text p.128)
exfoliation animation
exfoliation weathering - Google Images
5. Physical Weathering increases the
surface area and allows chemicals to
break rock apart faster.
(see text p.127)
[diagram]
vidclip- mechanical or physical weathering
B. Chemical Weathering: changes
the chemical composition of the rock.
1. Water (H2O) is the most important
agent of chemical weathering
 H2O combines with minerals and
weakens them.
Ex. Feldspar + Water → Clay + Salt
(makes oceans salty)
 H2O speeds up the rate of all other
chemical reactions.
 H2O absorbs gases such as oxygen
(O2) or carbon dioxide (CO2) that
weaken or dissolve rock.
2. Oxygen combines with iron rich
minerals to form iron oxide or rust.
Iron + O2 → Iron Oxide (rust)
rock oxidation - Google Images
3. Carbon Dioxide dissolves in water
to form Carbonic Acid.
[Demo- form carbonic acid]
This dissolves rocks, especially
limestone, forming caverns and
sinkholes (text p. 177, 179).
image karst topography
Observe an animation of cave formation.
Example: Howe Caverns in N.Y.
Howe Caverns: Year Round Adventure
ES 2008-09\Unit 4 08-09\Cave_Formation.asf
YouTube - Planet Earth - Caves 1/5
Chemical_Weathering.asf
C. Factors affecting how fast rocks
weather.
1. Mineral Composition
ex.: see text p.129 fig. 6
gravestone weathering - Google Image Search
 More resistant rocks stick out as
less resistant rocks weather away.
[Diagram]
buttes - Google Image Search
rock strata- grand canyon
2. Climate
 Rocks weather fastest in warm,
moist climates.
 Rocks weather slowest in dry
climates.
mayan pyramid
egyptian pyramids
3. Air Pollution, especially Acid
Rain, weathers rocks faster.
See text p.130
Cleopatra's Needle in Central Park- NYC
“Cleopatra's Needle, an Egyptian
obelisk, has been used for illustration
of weathering processes in numerous
geology textbooks (Figure 15). The
obelisk was donated to the United
States and erected at its site on the
west side of the Metropolitan Museum
of Art in 1881.
The monument is easy to find by
following any number of park trails
that lead toward the southwestern
side of the museum. The monument's
name, Cleopatra's Needle," is
somewhat of a misnomer. Inscriptions
on the monument include the names
Thutmose III and Rameses II from the
12th Century BC (more than 11
centuries before Cleopatra).
The obelisk is carved from a single
piece of red granite derived from a
quarry at Aswãn, and weighs about
224 tons. The surface of the stone is
heavily weathered, nearly masking the
rows of hieroglyphs engraved on all
sides.
closeup heiroglyph
Photographs taken near the time the
obelisk was erected in the park show
that the inscriptions were still quite
legible.
Cleopatra's Needle in Egypt 1880
The stone had lain in the Egyptian
desert for nearly 3000 years but
undergone little weathering. In a little
more than a century in the climate of
New York City, pollution and acid
rain have heavily pitted its surfaces.”
From: 3dparks.wr.usgs.gov/nyc/parks/loc1.html
D. Soil forms from the weathering of
rocks.
1. Composed of four parts:
 Inorganic: tiny fragments of
weathered rock
 Organic: decayed remains of
plants and animals.
Organic part also called Humus.
Makes soil dark colored and
fertile.
Creating humus: compost pile
compost - Google Image Search
 Air
 Water (see text p.133)
2. The type of Soil that forms depends
on a number of factors
(see text p.135-137, 139 read aloud).
3. Over time a mature soil can form
made of layers or Soil Horizons.
Soil Profile
[Diagram]
(See text p.138)
photo- soil profile
Earth Science Interlude: Big Wave Surfing- Eddie Aiku TournamentHawaii
http://www.youtube.com/watch?v=fcPsXrzwS3A&NR=1
http://www.youtube.com/watch?v=k2vkwy2vdP4
II Erosion: is the movement of
sediments by gravity, water, wind,
and/or ice.
A. Gravity is the driving force of
all erosion.
(Gravity makes water/ice flow and
wind blow)
Mass Movement occurs when
gravity transports sediment all by
itself.
Mass_Wasting.asf
Types:
1. Creep: slow movement of
sediments down a hill. (text p. 147)
[Diagram]
image: creep
2. Slumping: faster movement
downhill. (text p. 146)
3. Landslides and Mudflows: are
the fastest movement of sediment
downhill. Very dangerous.
landslide vidclip- Japan
YouTube - La Conchita Landslide
kayak landslide
YouTube - Landslides
B. Running Water, in streams and
rivers, transports more sediment than
any thing else!
http://www.youtube.com/watch?v=vpmOl-_JAqg
“Water is the main agent
of erosion on Earth.”
image of medium sized stream
1. Stream Velocity is how fast the
water is flowing.
 The greater the slope (or gradient)
of the land, the greater the stream
velocity. (text p.157)
[Graph]
 Stream velocity is greatest in the
center, a little below the surface.
This is where friction is least
(text p. 160)
[Diagrams]
2. Stream Discharge is the amount
(or volume) of water being carried.
The greater the discharge, the greater
the stream velocity (text p.161)
[Graph]
Amazon: image
Congo: Google Image Result for http://www.socialstudiesforkids.com/graphics/congorivermap.jpg
Yangtze: image
Mississippi: http://www.mapofmississippi.com/images/maps.jpg
C. Erosion by Flowing Water
1. Streams erode sediments in three
ways:
 Ions (salts) dissolve and are
carried in solution.
 Colloids, Clay, and Silt are
carried in suspension (floating)
 Sand, and larger sediment
bounce and roll along the bottom.
This is called the Bed-Load.
[Diagram]
Fig. 10.14 - Modes of Sediment Transport
2. The greater the discharge, the
greater the total sediment load
transported.
image mississippi river
[Graph]
Vidclip- stream erosion
3. The greater the velocity of a
stream, the greater the size of the
sediment eroded.
(see ESRT p.6)
esrt page 6
Practice:
4. The bed load can cut down through
the stream bottom forming
V-shaped canyons.
v shaped valley - Google Search
Case Study: The Grand Canyon
grand canyon - Google Search
[Diagrams]
http://www.youtube.com/watch?v=ktf73HNZZGY&feature=related
YouTube - Grand Canyon Adventure: River at Risk IMAX Trailer
vidclip- Grand Canyon
C. Erosion by Ocean Waves
1. Waves erode rocky shorelines to
form cliffs, sea arches, and sea stacks.
(text p.464- read).
2. On sandy beaches, sediment is
transported by Longshore Drift.
See Text p. 463-464
[Diagram]
YouTube - Longshore Drift 1
YouTube - Longshore Drift
Case Study: Long Island South Shore
http://www.fireislandmgm.com/00fi_beach.jpg
http://www.lib.utexas.edu/maps/national_parks/fire95.jpg
http://www.loving-long-island.com/image-files/fire-island-lighthouse-looking-west.jpg
http://lighthousegetaway.com/lights/NY/fire2.jpg
[Diagram]
Google Maps- Long Isand South Shore
Wave erosion_
See ESRT p.6:
1. State the name of the maximum
size particle that can be transported by
a stream moving at 400 cm./s.
2. State the name of the maximum
size particle that can be transported by
a stream moving at 200 cm./s.
3. State the name of the minimum
size sediment that can be transported
by a stream moving at 200 cm./s.
D. Erosion by Wind is most
important on beaches and deserts.
1. Sediment often deposited in Dunes.
(See Text p. 205-207)
2. Wind blown sediment can carve
rock into strange shapes.
Ex. “Hoodoo’s”
[Diagram]
wind erosion 1
wind erosion 2
wind erosion 4
vidclip: Wind Erosion 1
vidclip: Wind erosion 2
E. Erosion by Ice
1. Glacier: a mass of ice, formed
on land, that slowly flows down hill.
(See text p. 187-198)
Vidclip- glaciers 1
Glaciers form when snow does not
completely melt in summer and builds
up from year to year.
Two Types:
 Alpine or Valley Glaciers: form in
mountains and flow slowly
downhill. (Text p.187,188, 190)
glacier Images
alpine glacier 1
vidclip- lame lapse valley glacier
[Diagram]
Flowing ice carves V-shaped river
valleys into a U-shape. (text p.193)
[Diagram]
Image U shaped valley 1
u shaped valley 2
u shaped valley 4
 Continental Glaciers are huge
sheets of ice that cover all or part of
a continent. (text p. 189, 198)
[Diagram]
glacier Animations and Movies: cross section
2. Glaciers erode sediments of all
sizes.
 Some sediments are carried on top.
(text p.195)
 Some rocks freeze into the sides or
bottom of ice.
These often scratch and polish the
underlying bedrock. (text p.,192).
glacial straitions central park
[Diagram]
vidclip- glaciers 2
III Deposition: the laying down of
sediments in a new location.
A. Factors Effecting Deposition in Water
1. Larger particles, settle faster than
smaller particles.
[Diagram: Graphs]
2. Smallest particles may stay in
suspension (floating) or solution
(dissolved) and never settle.
3. If unsorted particles ( a
mixture of sizes) are added to water…
Largest (most coarse)will settle on
bottom...
and smallest (most fine) on top.
[diagram: vertical Sorting]
This is called Vertical Sorting or
Graded Bedding.
graqded bedding 1
graded bedding 2
graded bedding 3
4. When a stream enters a lake or
ocean, it slows down and deposits
sediment.
 Largest particles are close to shore
 finest are furthest from shore.
 This is called Horizontal Sorting.
animation Observe how sediments are deposited.
[diagram]
5. Denser particles, settle faster
than less dense particles.
6. Rounder particles settle faster
than flatter particles.
[Diagrams: Sorting by Shape]
[Graphs]
7. Life History of a Stream
 Youthful near the Source.
(See text p.157,167)
Steep slope, (high gradient)
High velocity,
Many rapids and waterfalls.
Bed load cuts steep V-shaped valleys
[Diagrams]
youthful 1
youthful 2
youthful 3
 Mature Stage (see text p.163)
Less slope, less velocity
Greater Discharge
Greater sediment load (text p.165)
Wide curves called Meanders form.
[Diagrams:erosional/depositional systems]
mature 1
mature 2
mature 3
YouTube - Sticky - One Minute on Meanders
 Old Age Stage (text p.168)
Very low gradient (slope)
Very high discharge
Very high sediment load
Ox-Bow Lakes or Bayou’s form.
[Diagrams]
old age 1
old age 2
old age 3
animation Meander Cut-Offs and Oxbow Lakes
8. Delta’s form when a stream or
river enters a lake or ocean.
(see text p.166)
[Diagram]
delta 1
mississippi delta 2
mississippi river delta 3
The_Mississippi_Delta_asf.asf
C. Wind deposited sediments are
often
 Angular [dia]
 show cross bedding.
[Diagram]
D. Evidence of Deposition by Ice
1. Sediments deposited by glaciers
are
 angular (have sharp corners)
and are
 poorly sorted (mixed up sizes).
These deposits are called Glacial Till.
(see text p.194)
[Diagram]
image glacial till
glacial till 2
glacial till 3
2. Long hills of glacial till mark
furthest advance of glacier.
These called Terminal Moraines.
moraine 1
moraine 3
3. Flat sandy areas, deposited by
streams flowing from melting glaciers
called Outwash Plains
outwash plain 1
outwash plain 2
outwash plain 3
4. Many lakes form from melting
blocks of ice.
glacial lake 2
glacial lake 3
5. Large boulders dropped by
melting ice called Glacial Erratics
[Diagram]
erratic 1
erratic 3
E. Glacial Features of Long Island
[diagram]
LI moraines
view of Ronkonkoma moraine
Ronkonkoma moriane- Montauk
Ronkonkoma moriane 2
F. Other glacial landforms: see text
p.193,197
YouTube - Glacial Erosion Landforms