Download G6 U9 Erosion and Deposition Cscope ppt

The Process of Erosion
and Deposition of
Sediments
Erosion and Deposition
• The transportation and
relocation of sediments
weathered from rocks
Erosion
• The moving of rock material from one
place to another
• For erosion to occur, three processes
must take place: detachment, lifting of
the particles, and transport.
• There are at least seven processes that
can cause erosion.
Erosion by Wind
• Small sediments can be carried in the air by
the wind.
• Larger sediments can be rolled along the
ground.
• Suspended particles may impact solid
objects, causing erosion by abrasion.
• Examples: sand dunes, desert pavement,
loess
Wind
Erosion by Water
• Fast moving water has a lot of energy and can
carry larger pieces of rocks and sediments.
• Slow moving water has less energy and can only
carry tiny particles of sediment.
• When water loses energy, the sediments settle
out.
• Water has the ability to materials over long
distances.
• Examples: canyons, gullies, rills, deltas, splash
erosion
Water
Erosion by Waves
• The relentless pounding of waves causes erosion
in several ways.
• Grinding of materials brought by the waves
against the shore. This forms sand. This can take
over 100 years.
• Action of saltwater on the minerals in the rocks
causes chemical changes in the rock by dissolving
the minerals.
• Strong waves carrying sand strikes the base of a
cliff undercutting or breaking the rock.
Waves
Erosion by Gravity
• Downward movement of rock and sediment
down a slope due to the pull of gravity
• The process is quite slow and almost
impossible to see until the land mass is no
longer able to support itself and falls or slides
down a slope.
• Examples: landslide, slump, mass wasting,
sinkhole, creep
Gravitational Erosion
Erosion by Glacial Ice
• Ice moves and carries rocks, grinding the rocks
beneath it.
• Plucking happens when materials are picked up
by the moving ice and pushed along by the
glacier.
• During abrasion, smaller rocks act like large
pieces of sand paper and cause grooves to be
carved into the land.
• Huge U-shaped valleys are cause by continental
glaciers.
Ice
Erosion by Bioerosion
• Bioerosion is the erosion of ocean
rocks by living animals.
• This is done by boring, drilling,
rasping, or scraping.
• Most often done by some mollusks,
sponges, chiton, urchins, algae,
bacteria, and fish
Bioerosion
Deposition
• The laying down or dropping off of
sediments that were carried to a new
location from another location
• Deposition can be transported by wind,
water, or ice.
Deposition by Wind
• Wind can transport material suspended in the
air, hundreds of km from its original location.
• Heavier materials may be pushed along the
ground.
• Material is deposited when the wind changes
direction or loses its kinetic energy.
• Obstacles, man-made or natural, will often
determine where the deposition occurs and the
type of feature formed (Ex: dunes, ripples)
Wind
Deposition by Water
• Water will carry sediments until the flow
slows down enough to drop the sediments.
• Larger particles are deposited near the
shore. Smaller particles settle out farther
from the shore.
• Deposited materials can be seen in river
beds, deltas, mud flats, and sand bars.
Water
Deposition by Ice
• Melting glaciers leave materials behind.
• Includes huge boulders (erratics), piles of
smaller rocks (moraines), glacial lakes, clay,
and sand (till)
• Glacial flows become slower if input is
reduced or when the ice begins to melt.
Ice