Transcript Water Erosion and Deposition

Chapter 8
A
process that wears away surface
materials and moves them from one
location to another
 Causes of erosion:
a.
b.
c.
d.
Gravity
Water
Wind
Glaciers
 Deposition-
the “dropping” of sediments
that have been eroded or weathered away
 This is the final step in the erosion process.


Mass movement – when gravity alone
moves materials down slope
Four types:
a.
b.
c.
d.
Slump
Creep
Rockslides
Mudflows
 Mass
movement that happens when loose
materials or rock layers slip down a slope
 Gets
name from way
sediments inch down
a hill
 Look for slopes where
trees, poles or fences
lean downhill
 The entire hill moves
downward slowly (like
an inch per year)
 Large
blocks of rock break loose from
steep slope, start falling, crash into more
rocks, knock them loose, etc.
 Often occur in winter because of freezing
& thawing in cracks causing fractures
 Thick
mix of sediments and water flowing
down a slope
 creep
clip
 Rockslide in Tennessee
 Mudslide in Italy
 Runoff
 Stream
and River
 Ocean Shoreline
 Groundwater
 Water
that doesn’t soak into the ground
or evaporate; it flows across the Earth’s
surface
 Can create rills, gullies, or sheets
Rills
Gully
Sheet
Results of water erosion: Combined
 Water
flows along a channel
 Water picks up light sediments and moves
them
 Large, heavy things just roll along the bottom of
the channel
 Heavy things scrape and bump against bottom
and sides of channel
 Stream continues to cut a deeper and wider
channel
 Alluvial
fan: shaped like a triangle
 Delta: sediments not deposited until
river enters ocean, gulf, or lake
Alluvial fan
Delta
 Waves
move sediments back and forth,
eroding and re-depositing sediment
 Beaches are a result of sand being
deposited
 Waves can also erode rocky cliffs to make
caves
 Water
that soaks into the ground and fills
holes in rocks below the surface
 Can create wells, springs, and geysers
 Water
mixes with carbon dioxide to form
a weak acid
 Limestone is easily dissolved by acid, so
as acidic groundwater moves through
cracks, the cracks are enlarged until a
cave is formed
 Air
movement picks up loose materials
and transports them
 Deflation: wind removes small particles
such as clay, silt, and sand, leaving
behind coarse materials
 Abrasion: when windblown sediments
strike and erode rocks
 Wind erosion usually happens in deserts,
beaches, and plowed fields
A
mound of sand
drifted by the wind
 Windward side has a
gentle slope
 Leeward side has a
steeper slope
 Windbreaks:
• People plant vegetation to reduce wind erosion
and trap snow moisture
• Grasses make good root systems on steep
slopes and on the coastline
• Moving mass of ice and snow is a glacier
• Snow piles up, compressing the ice on bottom
• Ice partially melts & becomes putty-like
• Whole mass begins to slide on putty layer and
moves downhill
 Plucking: ice
cracks rocks, pieces are
lifted up by the glacier
 Grooves: rocks scrape the dirt under the
glacier leaving long parallel grooves
 Striations: smaller scrapes than grooves
 Cirque: bowl-shaped hole left by glacier
 Arete: ridge formed when two glaciers
erode mountain from different directions
 Horn: sharp peak left by multiple glaciers
eroding mountain
 Till:
mix of sediment left at glacier base
 Moraine: ridge of sediment left in front of
the glacier when it stops pushing forward
 Outwash: sediment deposited by melted
water from the glacier
 Kettle: lake left behind by the glacier