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!