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  1. 1. 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
  2. 2. 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
  3. 3. 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)
  4. 4. 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 Discharge Solution Suspension
  5. 5. 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