weathering of rocks hoodoos more resistant layer
TRANSCRIPT
Weathering of RocksWeathering of Rocks
Hoodoos
More Resistant layerMore Resistant layer
Breaking and Removing rock1. Weathering - the disintegration and
decomposition of rock at or near the
surface.
2. Erosion – the transport of weathered
material by water, wind, ice and
gravity.
Weathering in the Rock Cycle
SedimentaryRocks
IgneousRocks
MetamorphicRocks
Magma
Sediment
Pressure And Cementation
Weathering and Erosion
Weathering
And Erosion
Heat and Pressure
CoolingHeat
Heat
Pressure
Wea
ther
ing
And
Ero
sion
*Types of Weathering*Types of Weathering
Mechanical –Mechanical – physical breakdown of physical breakdown of rocks with rocks with NO changeNO change in in composition.composition.
Chemical –Chemical – chemical alteration and chemical alteration and decomposition of rocks by decomposition of rocks by chemical reactions.chemical reactions.
Mechanical Weathering makes smaller pieces and exposes more
surface area to weathering processes
*Types of Mechanical Weathering*Types of Mechanical Weathering
1.1. Ice Wedging – water freezes in cracks and Ice Wedging – water freezes in cracks and expands them causing rocks to break expands them causing rocks to break apart.apart.
Ice Wedging
*Types of Mechanical Weathering*Types of Mechanical Weathering
2. Organic Activity – roots break apart rocks.2. Organic Activity – roots break apart rocks.
Organic Activity
Tree along 460 near Princeton that was saved Tree along 460 near Princeton that was saved by building a huge cement wall with drainageby building a huge cement wall with drainage
*Types of Mechanical Weathering*Types of Mechanical Weathering
3. Exfoliation and Jointing because of 3. Exfoliation and Jointing because of pressure release also break apart rocks.pressure release also break apart rocks.
Exfoliation
Exfoliation
Results of Jointing
*Types of Mechanical Weathering*Types of Mechanical Weathering
4. Abrasion –rounding or smoothing by 4. Abrasion –rounding or smoothing by water, wind, or glacierswater, wind, or glaciers
Wind, water and glaciers also Wind, water and glaciers also erode/deposit sediments.erode/deposit sediments.
Examples: Glacial Striations
Glacial Polish
Glaciers smooth and/or scratch
rocks.
*Water transport in rivers *Water transport in rivers smooths and rounds rocks. smooths and rounds rocks.
*Wind creates ventifacts *Wind creates ventifacts (smoothed surfaces and (smoothed surfaces and
erosion)erosion)
Wind and water work together
*Wind Deposition creates Dunes
*Types of Chemical Weathering*Types of Chemical Weathering Hydrolysis - any reaction in which
water participates. Also includes acid.
*Types of Chemical Weathering*Types of Chemical Weathering
1. Rust (oxidation) – caused by water and 1. Rust (oxidation) – caused by water and
oxygenoxygen
2. Carbonation (caves) – KARST topography 2. Carbonation (caves) – KARST topography
forms when carbonic acid (formed by forms when carbonic acid (formed by
water and carbon dioxide) reacts with water and carbon dioxide) reacts with
limestone (Calcium Carbonate) and limestone (Calcium Carbonate) and
converts it to converts it to solublesoluble Calcium Bicarbonate. Calcium Bicarbonate.
*2a. Stalactites and stalagmites form *2a. Stalactites and stalagmites form
from carbonate deposits from from carbonate deposits from dripping water in caves.dripping water in caves.
*2b. Sinkholes can also cause *2b. Sinkholes can also cause
pollution problems if they connect pollution problems if they connect directly to the water table.directly to the water table.
Typical SinkholeTypical Sinkhole
Not a Typical Sinkhole…Not a Typical Sinkhole…
*Types of Chemical Weathering*Types of Chemical Weathering3.3. Acids in mosses and roots can react with Acids in mosses and roots can react with
minerals in rocks minerals in rocks
and dissolve them.and dissolve them.
4.4. Changing of feldspar into clay (kaolin) by Changing of feldspar into clay (kaolin) by
hydrolysis.hydrolysis.
5.5. Dissolving by water.Dissolving by water.
*Factors influencing Weathering *Factors influencing Weathering RatesRates
1.Rock Composition – sedimentary rocks weather more rapidly than metamorphic or igneous. Also, quartz is resistant to weathering.
2.Rock Surface area – more surface exposed, more rapidly weathered.
3.Topography – high elevation and steep slopes weather more rapidly.
4.Climate – variable (freezes and thaws) and hot/ humid cause rapid weathering.
Benefits of WeatheringBenefits of Weathering
• Produces regolith (rock fragments) Produces regolith (rock fragments)
clay, sand, and gravel clay, sand, and gravel
• Produces mineralsProduces minerals
• Creates soilCreates soil
SoilSoil is made of loose, weathered is made of loose, weathered rock, minerals, air and organic rock, minerals, air and organic
material (humus).material (humus).
Soil Profile(fill in the blanks)Soil Profile(fill in the blanks)
RR
0- Leaf Litter0- Leaf Litter
B- Clay and B- Clay and Leached Leached MineralsMinerals
R-Bedrock or R-Bedrock or Parent Rock Parent Rock
A-HumusA-Humus
C- Partially C- Partially Weathered Weathered
BedrockBedrock
Soil ProfileSoil Profile
In a cross-In a cross-section of soil, section of soil,
various various horizonshorizons are formed.are formed.
AA Horizon: Topsoil Horizon: Topsoil
This layer is This layer is usually loose usually loose
and crumbly with and crumbly with a significant a significant amount of amount of
organic matter organic matter (HUMUS).(HUMUS).
((OO is leaf litter) is leaf litter)
AA Horizon: Topsoil Horizon: Topsoil
Most Most productiveproductive layer of soil.layer of soil.
ConservationConservation efforts are efforts are
focused here!focused here!
BB Horizon: Subsoils Horizon: Subsoils Subsoils are Subsoils are usually light, usually light,
dense, dense, clayclay-rich -rich with some organic with some organic
matter. This is matter. This is where where minerals minerals
leachedleached from the from the AA horizon horizon
accumulate.accumulate.
CC Horizon: Transition Horizon: Transition
Partially Partially weatheredweathered parent parent
material with material with little/no humus.little/no humus.
BedrockBedrock
Below the C Below the C horizon the horizon the
unweathered unweathered bedrockbedrock will be will be
found. found.
Climate and SoilClimate and Soil
TropicsTropics – thick, – thick, unfertile soils unfertile soils
called called laterites.laterites.Arctic or DesertArctic or Desert
– thin, made – thin, made mostly of mostly of regolithregolith
Topography and SoilTopography and Soil
SlopesSlopes – thin – thin
and dry topsoiland dry topsoil
LowlandsLowlands – thick, – thick,
wet soils with wet soils with
humushumus
Erosion Erosion ControlControl
Creating a Creating a soil soil condition condition that is that is resistant resistant to erosionto erosion
Control Practices and Control Practices and Structures for FarmsStructures for Farms
TerracingTerracing,,Crop Crop rotation rotation and Wind and Wind BreaksBreaks
Wind Erosion
Factors that Factors that DecreaseDecrease Wind Wind ErosionErosion
CloddinessCloddiness
Crop residueCrop residue
RidgesRidges
BarriersBarriers
Mass WastingMass Wasting
The downslope movement of unconsolidated Earth material due to gravity.
Increasing Severity of Mass WastingIncreasing Severity of Mass Wasting
Slump- quick downward movement of a block of soil.
Rock Slides
Creep-slow movement of soil down a slope due to expansion and freezing.
Creep
Mudflows-very fast downward Mudflows-very fast downward movement of water and mudmovement of water and mud
The StabilityStability of soil is reducedreduced by:
1. Adding water to the material of a slope
2. Increasing the steepness of the slope
3. Removing material from the lower
part of the slope
4. Earthquakes
5. Removal of vegetation (increases
runoff)
Erosion Erosion Created Created
LandformsLandformsMountainsMountains
erode to erode to peneplainspeneplains
Sometimes Sometimes monadnocks monadnocks (resistant knobs of rock)(resistant knobs of rock) are are exposed.exposed.
MountainsMountains erode finally to erode finally to plainsplains
Plateaus (large high flat areas)Plateaus (large high flat areas) erode to form erode to form mesas (smaller mesas (smaller high table-like structures)high table-like structures) and and buttes (small narrow buttes (small narrow columns)columns)
Engineering Solutions
Rock Nets
Soil Nailing
Avalanche Avalanche BarriersBarriers
(Switzerland)(Switzerland)
