Has This Happened To Your Yard?
Erosion and Deposition
Unit Essential Questions:
How does the Earth recycle and renew its surface?
How does society’s use of resources affect the quality of the environment?
!
Presentation Objectives:
§ Define erosion and deposition.
§ Identify the four agents of erosion.
§ Explain how the agents of erosion move and deposit sediment.
§ Explain how living organisms contribute to erosion.
Just Another Natural Process…
Q1
• Erosion: The process that transports Earth
materials from one place to another.
Q2
WWGG
• There are four major agents of erosion.
Wind
Water
Glaciers
Gravity
– After rocks are broken down by the different
weathering agents, the remaining material is
moved by the different erosion agents.
• After materials are eroded, they undergo
deposition.
– The sediments are placed down in a new
location.
• The confusion between weathering and erosion is
that the agents of erosion also weather rock.
Water: Streams and Rivers
Q3
What’s the Relationship?
• To be considered an erosional agent, the water
must be moving.
Q4
• Faster water carries
larger particles.
– On the land, we have streams and rivers.
– Faster water has
more energy!
• Faster water also
carries more
material.
• Streams and rivers weather through abrasion.
Stream and River Erosion
• Which will erode more: a river on a steep
slope or a river on a gradual slope?
Q5
Where does it all go?
Q6
• All rivers flow to the ocean.
– When it arrives, the river’s speed decreases!
• When the river slows down, the amount of
energy the water has decreases!
Deposition occurs!
• The first to be deposited will be…
– The larger particles!
A steeper river erodes more because the
water moves faster!
• There’s not enough energy to keep them
moving.
Sorted Sediment!
Q7
Going To The Beach!
Q8
• Ocean waves and tides
weather the coastline by
carving arches and cliffs.
• Coastal currents move
material along
coastlines.
The farther away from the shoreline you go, the
smaller the particles get!
Natural Interference
• Coastal erosion is a natural process that
can be altered by nature.
– Severe storms like hurricanes can greatly
alter the shoreline.
Q9
– Forms sandbars, barrier
islands, and hooks.
Human Interference
Q9
• It can also be enhanced by human activities.
– Jetties, breakwaters, etc.
– Built to stop longshore drift.
Fixes and causes problems!
Q10
Wind!
Dominates in areas with low precipitation
and high temperatures.
Three Options…
Q11
• Not many plants!
– Hold the soil in place
– Act as wind barriers to slow
the wind down.
• Wind can weather and erode!
• Suspension - Particles are carried in the air.
Deserts!
– Weathering: Wind causes particles to scrape against
rock, which is known as abrasion.
– Erosion: Wind picks up soil and moves it.
Glaciers!
Q12
• Saltation- Particles hop and bounce.
• Creep -Particles roll along the ground.
Small
Medium
Large
Impressive!
• A Glacier is a large
moving mass of ice.
• Glaciers weather rock by
scraping it as they move.
– Glaciers erode by
carrying lots of sediment
and large boulders.
About 20,000 years ago, New England was covered
by a glacier!
Gravity!
• Gravity is behind all of the
erosional agents.
– Without gravity…
• Glaciers wouldn’t move.
• Streams and rivers
wouldn’t flow.
• Gravity is responsible for mass movements.
• Some are slow…
• Creep
• Some are sudden…
• Landslides, mudflows,
and avalanches.
Q13
Don’t Forget Us!
Q14
• Animals erode the soil
when they burrow into it.
• Humans directly and
indirectly affect erosion.
– Directly: Move soil for
development
– Indirectly: Remove the plants
that hold the soil and act as
wind barriers.
Dust Bowl in the 1930’s!
WWGG always dominate!