Weathering, Erosion and Soils

Created by L. Zimmerman

3:00


Physical (AKA – Mechanical) –

Abrasion –

Frost Wedging –

Plants –

Exfoliation -

Chemical –

Carbonation –

Oxidation –

Hydrolysis–

=

the breaking of rock into smaller particles called sediment.

Types of WeatheringTypes of Weathering

Mechanical (physical)–causes a rock to crack or break into pieces without changing it chemically


Physical (AKA – Mechanical) –causes a rock to crack or break into pieces without changing it

chemically

Abrasion –

Frost Wedging –

Plants –

Exfoliation -

Chemical –

Carbonation –

Oxidation –

Hydration –

=



Physical Weathering

Abrasion sediments carried by streams and wind blown

sand cause particles to collide into each other and the surrounding rock.



chemically

Abrasion – Bump & Grind (streams/wind) smooth rounded particlesFrost Wedging –

Plants –

Exfoliation -

Chemical –

Carbonation –

Oxidation –

Hydration –

=



Physical WeatheringFrost wedging

water seeps into the cracks in a rock and freezes causing the ice to expand.


Physical (AKA – Mechanical) –causes a rock to crack or break into pieces without changing it chemically

Abrasion – Bump & Grind (streams/wind)Smooth, rounded particles

Frost Wedging – water seeps into the cracks in a rock and freezes causing the ice to expand

Plants –

Exfoliation -

Chemical –

Carbonation –

Oxidation –

Hydrolysis–

Acid Rain -

=



Physical Weathering

Plants Trees and shrubs can

grow through cracks in rocks.

Their roots wedge into crevices.



Abrasion – Bump & Grind (streams/wind)


Plants – roots wedge into rock and grow (expand)

Exfoliation -

Chemical –

Carbonation –

Oxidation –

Hydrolysis–

Acid Rain -

=



Physical Weathering

Exfoliation –cycle of heating and cooling causes the rock to expand & contract so it breaks off in slabs or layers.


Abrasion – Bump & Grind (streams/wind)


Plants – roots wedge into rock and grow (expand)

Exfoliation – Freeze & Thaw causes rock to “peel”

Chemical –

Carbonation –

Oxidation –

Hydrolysis–

Acid Rain -

=



Chemical – Any process that causes rocks to breakdown by chemical action and results in a change in the minerals (chemical composition).

Types of Weathering



chemically

Abrasion –

Frost Wedging –

Plants –

Exfoliation -

Chemical – involves water + it changes the rocks chemical composition

Carbonation –

Oxidation –

Hydration –

=



Chemical Weathering

Carbonation – carbon dioxide in the atmosphere dissolves in the droplets of water that make-up clouds.

This forms a weak carbonic acid.

Carbonic acid reacts with certain rocks and minerals which include: calcite, limestone, marble and chalk.



chemically

Abrasion –

Frost Wedging –

Plants –

Exfoliation -


Carbonation – CO2 + H2O form weak acid that dissolves limestone

Oxidation –

Hydrolysis–

=the breaking of rock into smaller particles called sediment.


Chemical Weathering

Oxidation - Water + Oxygen = Rust


Chemical Weathering

Hydrolysis



chemically

Abrasion –

Frost Wedging –

Plants –

Exfoliation -


Carbonation – CO2 + H2O form weak acid that dissolves limestone

Oxidation – Rust

Hydration – Water dissolves mineral to clay

=


Chemical Weathering

Acid Rain – Gases produced by humans can dissolve in the water droplets of a cloud to produce acid rain. These acids include:

H2SO4 – sulfuric acid

HNO3 – nitric acid

Cleopatra’s Cleopatra’s NeedleNeedle

Over 3,400 years old & made of limestone – Installed in London and NYC in 1880’s

Photo shows before and after and effects of acid rain and rates of weathering!


chemically

Abrasion –

Frost Wedging –

Plants –

Exfoliation -


Carbonation – CO2 + H2O form weak acid that dissolves limestoneOxidation – RustHydrolysis – Water dissolves mineral to clayAcid Rain – pollution combines with water vapor produces weak acid that dissolves rocks.

=



Rates of Weathering

FAST SLOW

ClimateTemp & Temp & MoistureMoisture

Cold/Warm & DryCold/Warm & DryWarm & Wet = fast chemicalWarm & Wet = fast chemicalCold & Wet = fast physicalCold & Wet = fast physical

Rock TypeRock Type Igneous & MetamorphicSedimentary

Shale/siltstone – conglomerate - limestone

Sandstone Dolostone

Rates of Weathering

Climate is the major factor that affects the rate of weathering

Due to climate and different weathering processes, landscapes develop differently.

Arid Climate – angular,

sharp edges, little

vegetation

Rates of Weathering

Humid Climate – soft, rounded with

vegetation

Rates of Weathering


Rock Types – cause softer, less resistant rocks to wear away, leaving harder, more resistant rocks behind.

Limestone (A) is most resistant

Shale (B) is least resistant

Rates of Weathering


Looking Glass Falls near Ashville shows differential weathering.

Rates of Weathering


Rates of Weatheri

ngFAST SLOW

TIMETIME Underground/lesstimeUnderground/lesstimeAbove GroundAbove Ground

Particle Size Or Surface

Area

Large size or less surface area

Small size or more surface area

Rates of WeatheringParticle Size – As a rock breaks into smaller pieces, the surface area increases, and therefore the rate of weathering increases.

Products of Weathering

Solid Sediments

Colloids • very small solid particles and too light to settle in water.

Size by name and number

Products of Weathering

It may mean calcium and lime deposits on your shower or if you have a well, sulfur and rust stains in the sink.

Dissolved Minerals – cause the “hardness” in groundwater (and surface water).

Chemical Weathering

Carbonation – carbon dioxide in the atmosphere dissolves in the droplets of water that make-up clouds.

This forms a weak carbonic acid.

Carbonic acid reacts with certain rocks and minerals which include: calcite, limestone, marble and chalk.


Cave Details


Carlsbad Cavern, New Mexico

Rocks, Weathering, and Soil Formation

Click for Clip

Soil Formation Soil Profile Climate is one of the most

important factors in formation of SoilSoil.

Soil varies in composition, texture, structure, and color at different depths.

These differences help divide the soil into zones known as HorizonsHorizons.

A side view of these horizons create a soil PROFILEPROFILE.

Soil Composition O O Horizon: organic matter that has fallen on

the ground and is decaying A A Horizon: topsoil (aka humus). This is the

zone where surface water leaches into the layers below.

B B Horizon: subsoil (aka regolith). Layer immediately below the topsoil.

This layer gets nutrients through the process known as LEACHING, LEACHING, when water flows through the topsoil and pulls nutrients down with it.

C C Horizon: partially weathered rock. This is the bottom layer of soil. Below it is solid bedrock.

Life in Soil

Some organisms mix the soil and make spaces in it for air and water.

Other soil organisms make humus, the material that makes soil fertile. Humus forms through decomposition. Fertile soil is rich in nutrients that plants

need.

Soil Conservation Soil is one of Earth’s most valuable

resourcesresources because everything that lives on the land depends directly or indirectly on soil.

FertileFertile soil is valuable because there is a limited supply. Less than 1/81/8thth of the land on Earth has soils well

suited for farmingfarming.

Soil Damage and Loss Soil can become exhausted, or lose its fertility. Accelerated Soil Erosion Unwise Clearing Clearing and Farming Farming methods increase soil erosion. For example,

clearing forests forests and containing animals to small pastures small pastures destroys the soil protection of plants

Soil Lost To The Seas!!

Three Examples of Accelerated Soil Erosion: DeforestationDeforestation - ( clearing trees )

GullyingGullying – furrows in plowed land which causes water to run faster over the soil

Climate ChangesClimate Changes – excessive rain or wind

Soil Conservation IntercroppingIntercropping: crops planted in alternating bands Contour PlowingContour Plowing: soil plowed in circular motion with the lay of the

land TerracingTerracing: step-like ridges in sides of hills Crop RotationCrop Rotation: planting one crop one year and a different one next

year

Contour Plowing

Contour plowing is the practice of plowing fields along the contours of a slope.

This helps slow the runoff of excess rainfall and prevents it from washing the soil away.

Conservation Plowing

Conservation Plowing disturbs the soil and its plant cover as little as possible.

Dead weeds and stalks of the previous year’s crop are left in the ground to help return soil nutrients.

Definition: - Transporting or moving weathered sediments

Driving Force: GRAVITYGRAVITY

GLACIERSGLACIERS•Unsorted & loose

•Scratched•Polished•U- shape valleys

WATERWATER•#1 agent•Well sorted•Smooth •Rounded

GRAVITYGRAVITY•Unsorted•Mass wasting•Creep •Slump•Talus

HumansHumans•Farming•Mining•Deforestation

WAVESWAVES•Beaches•Longshore current•Jetties & Groins

WINDWIND•Arid Deserts•Dunes•Pitted/frosted


Erosion by Gravity

•The movement of SOILSOIL particles and RockRock fragments is called MASS MASS

WastingWasting.

•TALUS :TALUS : rock fragments that gather at the bottom of the slope.

• Rapid Mass Movements

• ROCKFALLROCKFALL: rocks falling from a steep cliff

•ROCK SLIDEROCK SLIDE: loose rock and soil moving down a slope

•MUD FLOWMUD FLOW: rapid movement of mud

•SLUMPSLUMP: large block of soil moving downhill in one piece


Erosion by Gravity

MUDSLIDEMUDSLIDE


Erosion by Gravity

SlumpSlump

Talus SlopeTalus Slope


Erosion by wind

Deposition

Factors affecting Factors affecting DepositionDeposition: :

SIZE SIZE VelocityVelocity

ShapeShape Gradient Gradient Density Density

DischargeDischarge

Water Deposits•Well Sorted•Rounded

•Smooth•Abrasion

Vertical SortingVertical Sorting – In a quiet body of waterLoss of velocityBig gets dropped first

Horizontal SortingHorizontal Sorting – Stream enters lakeLoses velocitySediments depositedBig – close to shoreSmall – Far from shore

The settling or dropping of particles after being picked up by an agent of erosion Wind works the same way


DepositionSizeSize – As the size of sediment increases, the rate of

deposition increases.


Deposition

DensityDensity – As the density of sediment increases, the rate of deposition increases.

ShapeShape – The flatter the particle the slower the deposition.


As Velocity goes upup – Erosion goes upup and Deposition goes downdown

As Gradient gets steepersteeper – Erosion goes upup and Deposition goes downdown

As Discharge increasesincreases – Erosion goes upup.

Deposition

Deposition

When a stream enters a body of water, its speed will decrease, and therefore the deposition of sediments occurs.A deposit at the mouth of

a stream where it enters a large body of water is called a delta.


A delta is an example of the horizontal deposition of sediments in the water.

Clay

Boulders Cobbles

PebblesEvidence of Sorted Sediment

Deposition


Wind DepositsWind Deposits

•Similar to water

•Loss of velocity will result in deposition by size

•Well sorted

•Graded bedding

Velocity = FAST - ErosionVelocity = FAST - Erosion

Velocity = Slow - DepositionVelocity = Slow - Deposition

Erosional/Depostional Systems

RIVERS

YOUNGYOUNG

OLDOLD

MATUREMATURE

V shaped valley

Fast

Steep

Straight

Rapids & Waterfalls

Medium slope

Slight curves

Medium speed

Narrow floodplain

Small rapids

Flat

Slow

Lots of meanders

Straight

Wide floodplain & Channel


Erosional/Depositional Systems - Rivers


The bends in a stream’s channel are called meanders




Arial Map View of a stream Channel


Outside of the curve= velocity increase = more erosion.

Inside of the curve= velocity decrease = deposition.



DepositionDeposition

ErosionErosion



Formation of Oxbow Lake – the work of erosion and deposition



Erosional/Depositional Systems - Glaciers Glaciers can really

move a lot of materialmove a lot of material, dramatically changing the surface of the earth.

2 Types:2 Types:

Continental – covered North America over 10,000 years ago and is the cause of finger cause of finger lakes and Morraines lakes and Morraines (like Long Island)!(like Long Island)!

Alpine – in mountains Create U-ShapedU-Shaped valleys


Erosional/Depositional Systems - Glaciers


Erosional/Depositional Systems - GlaciersContinental GlacierContinental Glacier

GLACIERSFeatures:

Alpine GlacierAlpine Glacier

Unsorted, loose depositsGround up rock flour or glacial tillMorainesU-shape ValleysKettle lakes, drumlins, outwash plains

Moved from the north (pole) to the south

Move downhill!


Erosional/Depositional Systems - Glaciers Glacial Features

A. Terminal Moraine

B. Lateral Moraine

C. Glacial stream

D. Outwash plains

E. Braided streams

F. U- Shaped Valleys


Erosional/Depositional Systems - Glaciers

During Glaciation

Post - Glaciation

Its a U shape valley!Its a U shape valley!


Drumlins


Formation of Long Island

Formation of Formation of Finger LakesFinger Lakes


Landscape Development

How is the Earth’s surface shaped by weathering, erosion and deposition?



Landscape: A region on the Earth’s surface in which physical features, such as hills, valleys, and streams are related by a common origin (it simply means “scenery”)

Three (3) main types: Mountains, Plains and PlateausMountains, Plains and Plateaus



MountainsMountains

Greatest relief between their peaks and valleys

Created by tectonic forces (igneous and metamorphic rocks)

Steep mountain slopes have fast erosive streams acting on them, creating deep valleys and waterfalls


Landscape DevelopmentPlateaus

Low relief (flat) High elevation Horizontal rock formations

NC Piedmont



Plains (lowlands)Plains (lowlands) Have the least relief Generally flat and low elevations Underlain by flat layers of sedimentary rock

HumansHumans

Tectonic ForcesTectonic Forces

ClimateClimate

TimeTime

Crustal MaterialsCrustal Materials

Humid

LANDSCAPELANDSCAPE

DEVELOPMENTDEVELOPMENT

ARIDARID

Weathering, Erosion and Soils

Technology

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