Has This Happened To Your Yard?
Erosion and DepositionUnit 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…• Erosion: The process that transports Earth
materials from one place to another. – 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.
Q1 WWGG• There are four major agents of erosion.
Q2
Wind Water Glaciers Gravity
• The confusion between weathering and erosion is that the agents of erosion also weather rock.
Water: Streams and Rivers Q3
• To be considered an erosional agent, the water must be moving. – On the land, we have streams and rivers.
• Streams and rivers weather through abrasion.
What’s the Relationship?
• Faster water carries larger particles. – Faster water has
more energy!
• Faster water also carries more material.
Q4
Stream and River Erosion• Which will erode more: a river on a steep
slope or a river on a gradual slope?
A steeper river erodes more because the water moves faster!
Q5 Where does it all go?
• The first to be deposited will be… – The larger particles!
• There’s not enough energy to keep them moving.
• 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!
Q6
Sorted Sediment!
The farther away from the shoreline you go, the smaller the particles get!
Q7Going To The Beach!
• Ocean waves and tides weather the coastline by carving arches and cliffs.
Q8
• Coastal currents move material along coastlines. – Forms sandbars, barrier
islands, and hooks.
Natural Interference• Coastal erosion is a natural process that
can be altered by nature. – Severe storms like hurricanes can greatly
alter the shoreline.
Q9 Human Interference
• It can also be enhanced by human activities. – Jetties, breakwaters, etc. – Built to stop longshore drift.
Fixes and causes problems!
Q9
Wind!
• Not many plants! – Hold the soil in place – Act as wind barriers to slow
the wind down.
Q10
Dominates in areas with low precipitation and high temperatures.
• Wind can weather and erode! – Weathering: Wind causes particles to scrape against
rock, which is known as abrasion. – Erosion: Wind picks up soil and moves it.
Deserts!
Three Options…
• Suspension - Particles are carried in the air.
• Saltation- Particles hop and bounce.
• Creep -Particles roll along the ground.
Q11
Small
Medium
Large
Glaciers!
• Glaciers weather rock by scraping it as they move. – Glaciers erode by
carrying lots of sediment and large boulders.
Q12
• A Glacier is a large moving mass of ice.
Impressive!
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.
Q13
• Some are slow… • Creep
• Some are sudden… • Landslides, mudflows,
and avalanches.
• Gravity is responsible for mass movements.
Don’t Forget Us!
• Animals erode the soil when they burrow into it.
WWGG always dominate!
Q14
• 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!
