Earth Science Review for test

Erosion I. Erosion

A. transportation of rock, soil, and minerals particles from one place to

another.

• Erosion is done by water, wind or ice.

• The key ingredient behind all the agents of erosion is

GRAVITY.

• What is a transportation system?

– This includes all agents involved in erosion and

weathering

• Transportation agent

• Energy

• And the material moved

II. What proofs do we have that sediments move?

A.There are two main proofs

• Transported Sediments

– The very fact that the sediments are found in places

away from it’s origin

– Beaches along the coast get its sand (transported

sediment) from mountains in the inland.

– They were brought from rivers and streams into the

ocean.

• Residual Sediments

– Is the material that remains at the location of the

weathering

– and transported sediments is the erosion product that

is moved from the source.

– In New York State there are more

transported sediments than

Residual

III. Properties of transported materials

Earth Science Review for test

• We just learned that there common transporting agents

– Ice

– Water

– Wind

• Transported material often contain

characteristics that tell us what

eroding force and form of

transportation was done

– Water tends to smooth and round out sediments

– Wind tend to be often pitted or “frosted” as a result of abrasions

during travel

– The longer the wind or water action occurs the smoother and

rounder the sediments become

– Ice ( glacier) sediments usually have scratches

on the surface due to being pushed and scraped

by ice

– Gravity alone the sediments are sharp edged

and angular.

• Can see this at the base of the mountains

V. There are many things that affect transportation

– Gravity

– Wind

– Ice

– Humans

– Gravity

– Most of the transportation systems are caused by

gravity

– Gravity as discussed before can work alone

– Loose pieces of rocks on the side of a slope

– Gravity also works with the other systems

Earth Science Review for test

– Especially water in a stream

– Water

– Running water is (stream) is the predominant form of erosion on

Earth

– As stream cut into the underlying bedrock they cut V shaped

valleys

– There are a number of factors that affect the way running water of a

stream transports sediments

VI. Water, velocity & Sediments

• In a stream channel the average speed

of running water increases with the increase of

Discharge

– Discharge – is the volume (amount) of

water in a given location during a

specific amount of time

– The relationship between the velocity and discharge is

interdependent.

• In the spring streams usually move faster because of the

melted ice and snow

– The velocity ( speed) of the water in a stream is directly effected to

the slope of the stream

– As the slope increases the velocity

increases

– The fastest water in a stream with a straight

course ( path) is in the center just below the

place where there is the least friction

– Meandering Stream is a curved stream

• The highest velocity is on the outside of the curve

• Therefore erosion is greater on the

outside of the curve (meander)

Earth Science Review for test

• Deposition ( deposit) takes place on the inside of the

meander (curve)

• Between the meanders is called a change over .

– Boundaries between erosion and deposition (leaving the

sediments) occur in many places of the length of the stream

• These boundaries usually occur

• Midstream in meanders and where changes of

velocity occurs

• Near the mouth of the stream

• Where nether erosion or deposition occur

– Friction

• The greater the amount of friction (force

found in between 2 surfaces that offers

resistance to motion) the slower the water is

• The more efficient channel is one that is

smooth and has a semicircular shape.

One more key point

- As the velocity of a stream

increases the size of the particles that can be

moved increases in two ways

• Solution – dissolved in the water

• Suspension – (sand, clay silt) by bouncing or

dragging these materials along the stream’s bed

( ground made out of pebbles, cobblers, and boulders

Words you have to know from these notes

Friction DischargeSolution Suspension

Earth Science Review for test

Channel Velocity Meandering stream

You should be able to answer questions in your book. If you can not answer some of them call me or email me over the weekend

9 -21