Weathering:-The Breakdown of rock due to physical or chemical changes

*TWO MAIN TYPES OF WEATHERING*

1) Physical Weathering:

-Changes the size or shape of a rock- for example, by breaking it into smaller pieces- without changing its chemical composition

Examples:

1)Frost Action:

- important agent of weathering in climates that experience above and below 0oC-water seeps into pores of rocks, freezes and therefore expands, causing cracks in the rocks.

- over an extended period of freezing and melting, the rock will crumble

Plant Roots:-Grow in the crack of rocks

Animals:-animals that burrow beneath the ground

-roots expand in the crevices of rocks and gradually push the rock apart

- constantly expose new rock surfaces to weathering

Abrasion:-rocks carried by a stream , bump and rub against one another. These collisions cause the rock to break down.

-wind, moving ice and gravity are also agents of abrasion.

CHEMICAL WEATHERING:- requires heat energy and often water

- changes the chemical composition of the rock, forming new substances.Ex:-Feldspars uplifted to the earth’s surface come in contact with water and chemically weather to clay.

-takes place more rapidly in warm and moist climates

-rusting of a nail: iron rusts in the presence of moisture. O2

combines with the iron atoms and forms rust

SOIL-the mixture of weathered rock and organic remains that cover bedrock.

- under natural conditions, both physical and chemical weathering play a part in soil development.Physical weathering; breaks solid rock into small particles

Chemical weathering: changes hard minerals into softer forms

- the decay of organic remains produce organic acids that accelerate chemical weathering

SOIL HORIZONS:

-created by the weathering of bedrock* the top layer is the best for growing crops. Rich in dark colored organic remains called humus

*ground water filtration does transport some minerals to the lower layers* the lowest layer of soil is generally composed of broken up bedrock.

ORGANIC MATERIAL

BROKEN BEDROCK-SOME ORGANIC MATERIAL

COMPLETELY BEDROCK

Important things to know about soil

* It takes 100 to 400 years for one centimeter of topsoil to form

* Destruction of plant cover and poor farming and mining practices leave soil exposed and unprotected. It is then quickly carried away by water and wind

Sediments:-rocks that have been broken into various sized fragments.

Erosion:Involves the transporting of sediments away from their place of origin and depositing them elsewhere

- running water transports sediments in several ways

1) Erosion by water :

- the smallest particles remain suspended in solution because they cannot be filtered out

- largest most dense particles are rolled or bounced along the streambed- low density material such as organic remains are carried along the surface of the water by flotation

- water velocity indicates transported particle size

Larger= greater velocity

smaller= lower velocity

The Velocity Of Streams

-as stream gradient and or water quantity increases,, velocity of water increases.* most erosion takes place when streams are in flood

- slowest moving water sticks to the inside of the bends, causing deposition on the inner banks

- fastest flowing water swings at the outside of river beds causing erosion along the outer banks.

Erosion By Wind

- wind can carry away sand silt and clay

-occurs mainly in dry areas such as deserts, because there is not much plant life to hold soil in place

-wind erodes by abrasion

Erosion by Ice:Glacier: large mass of ice that

moves due to its weight under gravity.

-as it moves, it picks up and carries loose rock material

-acts like a huge abrasion system

- when ice melts, unsorted deposits are left behind

- rocks are left angular and often scratched

WHAT IS DEPOSITION?

- occurs when agents of erosion, deposit or lay down particles and fragments of sediments

- Factors That Affect Deposition

Particle Size:

Smaller particles such as clay and silt, settle more slowly than cobbles and boulders

Particle Shape:Flat angular pieces of sediment settle more slowly because of their increased surface area and friction with the water.-smooth, rounded particles settle more quickly

Particle Density:Among particles of the same average size and shape, more dense particles settle faster.

Settling Rate and Settling Time:- as the rate of settling increases,

settling time decreases

Sorting of Sediments:Horizontal Sorting:

-largest, roundest and densest particles are deposited first near the oceans coastline, while the smallest, flattest and least dense are carried further form the shorelineVertical Sorting:

Where particles sort out from bottom to top in a layer

Deposition in Streams

- sediment can cause sand bars in slower sections of the stream

Deposition By Wind:

-Like running water, wind deposits sediments in layers

Ex. Sand dunes

SORTED DEPOSIT:

EX:

When streams slow down, largest particles settle out first , then smaller particles.

Deposition by Gravity:- does not create sorted

sediments. (many different sediment sizes mixed together.Deposition by

Glaciers:- occurs when glaciers melt and sediments are released.

- unsorted unless glacial sediments are deposited as a result of melt-water

NEW YORK AND THE ICE AGES-as recently as 20,000 years ago, most of New York was covered by a continental ice sheet.

Alpine Glaciers:-occur in mountain regions-will flow downhill under its own weight due mainly to slope.-Flow at a rate of a few centimeters to several meters per day-ice rubbing against surrounding

rock carves out valleys

Continental Glaciers- known as ice sheets- responsible for most glacial features in NYS- rock carried within the glacier that causes erosion of the land

Striations:Parallel grooves and scratches in bedrock