weathering, erosion, deposition, and landscapes forces at work forces at work forces at work © lisa...
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Weathering, Erosion, Weathering, Erosion, Deposition, and LandscapesDeposition, and Landscapes
forces at work
© Lisa Michalek
WeatheriWeatheringng
The The breakdowbreakdown of rocks n of rocks due to due to physical physical or or chemical chemical changeschanges
Physical WeatheringPhysical Weathering Changes the size and/or shape of a rock without Changes the size and/or shape of a rock without
changing the chemical compositionchanging the chemical composition In In frost actionfrost action, water seeps into cracks in rocks. , water seeps into cracks in rocks.
The water expands as The water expands as it freezes and makes it freezes and makes cracks in the rock a cracks in the rock a little larger little larger
When the When the ice melts and the liquid ice melts and the liquid evaporates, the rock evaporates, the rock is left more porousis left more porous
Over time, the freezing Over time, the freezing and melting in the cracks and melting in the cracks will cause the rock to will cause the rock to crumblecrumble
Physical WeatheringPhysical Weathering Plant roots grow in rock Plant roots grow in rock
crevices and gradually push crevices and gradually push the rock apartthe rock apart
Animals that burrow Animals that burrow beneath the ground will beneath the ground will expose new rock surfaces to expose new rock surfaces to weatheringweathering
AbrasionAbrasion occurs when rock occurs when rock particles are carried particles are carried in water, they in water, they bump and rub bump and rub against other rocksagainst other rocks
Chemical WeatheringChemical Weathering When rocks are exposed to the When rocks are exposed to the
atmosphere and hydrosphere, they atmosphere and hydrosphere, they often undergo changes in the often undergo changes in the chemical composition of rock, forming chemical composition of rock, forming new substancesnew substances
Usually requires heat and water to Usually requires heat and water to bring about chemical changesbring about chemical changes Therefore, it takes place more rapidly in Therefore, it takes place more rapidly in
warm, moist climateswarm, moist climates Observe an animation of cave formation.
Soil FormationSoil Formation Soil is a mixture of Soil is a mixture of
weathered rock and organic weathered rock and organic remains the usually covers remains the usually covers bedrockbedrock
The weathering of soil The weathering of soil produces horizon layersproduces horizon layers The top layer is usually the The top layer is usually the
best for growing crops best for growing crops because it is rich in organic because it is rich in organic remains called humusremains called humus
The next layer is usually The next layer is usually mineral enriched from mineral enriched from groundwater transporting groundwater transporting mineralsminerals
The lowest layer is composed The lowest layer is composed of broken-up bedrockof broken-up bedrock
Soil FormationSoil Formation
Erosion of SedimentsErosion of Sediments SedimentsSediments are rocks that have been are rocks that have been
broken into fragmentsbroken into fragments ErosionErosion is the transporting of is the transporting of
sediments away from their sediments away from their place of origin and place of origin and depositing them depositing them elsewhereelsewhere Gravity, water, Gravity, water,
wind, and ice wind, and ice erode sedimentserode sediments
Forces of Erosion and Deposition
The 1st type of Erosion and Deposition is: Gravity
-Causes the downward movement of sediments called mass movement
a. A sign of gravity erosion: Landslide – soil, rocks, & boulders move down a slope or off a cliff
Landslide (slow loading)
LANDSLIDE
Another sign of Gravity causing Erosion: :
b. Mudflow – water mixes with rock and soil and moves down a slope. Usually happens after rain and water content can be as high as 60%.
A sign of gravity erosion: Slump
Slump – loose, water-filled earth (permeable) sits on top of a water proof (impermeable) layer. The loose earth changes position.
Slump animation
Slump
Another sign of gravity erosion: Creep
is a very, very slow form of mass movement. It's just a slow adjustment of soil and rocks. Gravity always causes the rocks and soil to settle just a little farther down slope than where they started from.
Creep
Erosion by WaterErosion by Water The smallest particles are carried in The smallest particles are carried in
solutionsolution The largest and most dense particles are The largest and most dense particles are
rolled or bounced along the streambedrolled or bounced along the streambed Particles of low density, such as organic Particles of low density, such as organic
remains, are carried along the surface by remains, are carried along the surface by flotationflotation
Deposition waterfall
Velocity of StreamsVelocity of Streams The velocity of a stream is controlled by The velocity of a stream is controlled by
the slope and the amount of water flowing the slope and the amount of water flowing in the stream (in the stream (dischargedischarge). As velocity ). As velocity increases the kinetic energy also increases the kinetic energy also increases. increases.
As the stream gradient As the stream gradient increases, so does the increases, so does the velocity of the water velocity of the water flowing in the streamflowing in the stream
Velocity is also increased Velocity is also increased by an increase in the by an increase in the quantity of water quantity of water in the streamin the stream
Velocity of StreamsVelocity of Streams There is a direct There is a direct
relationship relationship between the between the velocity of a velocity of a stream and the stream and the size of the size of the particles it can particles it can transporttransport
Large grains of Large grains of sediment can sediment can only be eroded only be eroded by fast-moving by fast-moving waterwater
Velocity of StreamsVelocity of Streams Streams with broad, flat valleys often develop Streams with broad, flat valleys often develop
S-shaped curves called S-shaped curves called meandersmeanders At the bends in the stream, the fastest-At the bends in the stream, the fastest-
flowing water swings to the outside of the flowing water swings to the outside of the bends, causing erosion along the outer bankbends, causing erosion along the outer bank
The slowest moving water stays to the inside The slowest moving water stays to the inside of the bends, causing depositionof the bends, causing deposition
Meander oxbow lake waterfall waterfall
Erosion by WindErosion by Wind Wind can pick up loose rock materials, Wind can pick up loose rock materials,
such as sand, silt, and clay, and carry such as sand, silt, and clay, and carry them awaythem away
Wind erosion occurs mostly in dry areas, Wind erosion occurs mostly in dry areas, such as deserts and beachessuch as deserts and beaches
Sand blown by Sand blown by the wind can the wind can erode down erode down material on material on a rocka rock’’s surfaces surface
dune formationdune formation
Wind erosion happens when the soil is left unprotected from the strong winds. The loss of topsoil lowers the quality of the soil. This makes it more expensive and harder to grow good crops.
formation of an arch
Erosion by WindErosion by Wind
Erosion by IceErosion by Ice
If more snow accumulates in the winter If more snow accumulates in the winter than melts in the summer, the snow on than melts in the summer, the snow on the bottom turns to ice glacial retreatthe bottom turns to ice glacial retreat
If it becomes thick enough, its weight will If it becomes thick enough, its weight will cause it to move under the pull of gravitycause it to move under the pull of gravity
A A glacierglacier is a large is a large mass of moving icemass of moving ice
As a glacier moves, As a glacier moves, it carries, pushes, it carries, pushes, and drags loose and drags loose rock materialrock material
Erosion by IceErosion by Ice The glacier, with The glacier, with
pieces of rock, pieces of rock, smoothes, striates smoothes, striates (scratches), (scratches), and grooves bedrockand grooves bedrock
As a glacier moves As a glacier moves through a valley, it will through a valley, it will make a U-shape make a U-shape instead of a V-shape instead of a V-shape caused by watercaused by water
When the ice melts, When the ice melts, unsorted rocks and unsorted rocks and boulders are left boulders are left scattered around on scattered around on hilltops and sides of hilltops and sides of valleysvalleys
Plucking
Plucking occurs when ice flows into or refreezes in fractures in the bedrock. The ice wedges and removes blocks of bedrock and incorporates it into the glacier. This process is most rapid in areas where water is refreezing near the bed.
Plucking animation
Formed by a glacier
Formed by a glacier
HORN
Glacial Lake-formed by a glacier
DepositionDeposition
When an agent of erosion deposits, When an agent of erosion deposits, or lays down particles and fragments or lays down particles and fragments of earth materials (sediments)of earth materials (sediments)
Also called Also called sedimentationsedimentation Most deposition takes place in waterMost deposition takes place in water
Deposition FactorsDeposition Factors Particle SizeParticle Size
Smaller particles (clay and silt) settle Smaller particles (clay and silt) settle more slowly than cobbles and bouldersmore slowly than cobbles and boulders
Particle ShapeParticle Shape Friction between water and the surfaces Friction between water and the surfaces
of particles slows down settlingof particles slows down settling Smooth, rounded Smooth, rounded
particles settle particles settle more slowlymore slowly
Deposition FactorsDeposition Factors
Particle DensityParticle Density Denser particles settle faster, less dense Denser particles settle faster, less dense
particles take more time to settleparticles take more time to settle Settling Rate and TimeSettling Rate and Time
Sediments that settle at a Sediments that settle at a faster rate require less timefaster rate require less time
As the rate of settling As the rate of settling increases, the settling increases, the settling time decreasestime decreases
Sorting of SedimentsSorting of Sediments
HorizontalHorizontal sorting sorting occurs at the end of occurs at the end of streamsstreams The smaller sediments The smaller sediments
can be carried a greater can be carried a greater distance from shoredistance from shore
VerticalVertical sorting occurs when a sorting occurs when a landscape dumps a variety of landscape dumps a variety of particle sizes in to still waterparticle sizes in to still water
Deposition by WindDeposition by Wind
Usually sorts sediments by sizeUsually sorts sediments by size Cross bedding layers meet a different Cross bedding layers meet a different
anglesangles
Deposition by GravityDeposition by Gravity
At the base of a cliff, At the base of a cliff, where pieces of where pieces of weathered rock weathered rock have fallen, you will have fallen, you will find pieces of many find pieces of many different sizesdifferent sizes
The sediments are The sediments are not sortednot sorted
Deposition by GlaciersDeposition by Glaciers Occurs when a glacier Occurs when a glacier
melts and sediments melts and sediments are releasedare released
Glacial erraticsGlacial erratics are are large rocks that have large rocks that have been transported by been transported by glacial ice without being glacial ice without being broken into small broken into small particlesparticles They are often found They are often found
high above stream high above stream valleysvalleys
Rounding and striations Rounding and striations (scratches) indicate (scratches) indicate transport by glacierstransport by glaciers
Alpine GlaciersAlpine Glaciers
Also known as Also known as valley valley glaciersglaciers, , occur in occur in mountain mountain regions, and regions, and may carve may carve out U-shaped out U-shaped valleys with valleys with their moving their moving iceice
Continental GlaciersContinental Glaciers
Also known as Also known as ice sheetsice sheets causes causes sculpting of the sculpting of the land as rocks land as rocks are carried are carried within the within the glacier or glacier or dragged under dragged under the flowing icethe flowing ice
Glacial FeaturesGlacial Features
Glacial PolishGlacial Polish – – when glaciers act like when glaciers act like sandpaper, grinding sandpaper, grinding the jagged edges the jagged edges from the mountains from the mountains and smoothing hard and smoothing hard bedrock surfacesbedrock surfaces
StriationStriation – parallel – parallel grooves and scratches grooves and scratches in the bedrock left by in the bedrock left by the rocks in the the rocks in the glacierglacier
Glacial FeaturesGlacial Features DrumlinsDrumlins – accumulation of rock and soil – accumulation of rock and soil
that builds up in front of the flowing icethat builds up in front of the flowing ice
MorainesMoraines – where the ice front stops its – where the ice front stops its southward advance, piles of southward advance, piles of unsorted soil and rock remainunsorted soil and rock remain
Glacial FeaturesGlacial Features KettlesKettles – Low spots in the glacial – Low spots in the glacial
deposits and places where large, deposits and places where large, buried ice blocks melt leave these buried ice blocks melt leave these dry depressions dry depressions and ponds and ponds called called Kettle LakesKettle Lakes
North American North American Continental GlaciationContinental Glaciation
The Oceans and The Oceans and CoastsCoasts
Seawater covers almost 71% Seawater covers almost 71% of our planetof our planet
The average depth is about 4 km The average depth is about 4 km (3 mi)(3 mi)
One Liter of seawater One Liter of seawater contains about 3.5% of contains about 3.5% of dissolved solidsdissolved solids Sodium chloride (table Sodium chloride (table
salt) is the most commonsalt) is the most common When evaporation of ocean When evaporation of ocean
water causes the salts to water causes the salts to become too concentrated to become too concentrated to stay in solution, they are stay in solution, they are precipitated as sedimentprecipitated as sediment
The Oceans and CoastsThe Oceans and Coasts
The edges of the oceans are places of The edges of the oceans are places of change caused by the action of waves change caused by the action of waves and long shore currents long shore driftand long shore currents long shore drift
Beach sediments are rounded and Beach sediments are rounded and reduced in size by abrasion as the reduced in size by abrasion as the energy in the breaking waves causes energy in the breaking waves causes the particles to rub against one anotherthe particles to rub against one another
The Oceans and CoastsThe Oceans and Coasts Sand is often transported along the Sand is often transported along the
beach and just outside the breaking beach and just outside the breaking waves in the zone of waves in the zone of longshore longshore transporttransport
This movement of sand builds the This movement of sand builds the features of the features of the ocean shorelines ocean shorelines including sand bars, including sand bars, barrier islands, barrier islands, and sand spitsand sand spits
beach processesbeach processes
LandscapesLandscapes
A region on EarthA region on Earth’’s surface with physical s surface with physical features, such as hills, valleys, and features, such as hills, valleys, and streamsstreams
The shape (The shape (topographytopography) and ) and composition of the landscape is composition of the landscape is determined by the climate, bedrock, determined by the climate, bedrock, geologic structures, and human activitiesgeologic structures, and human activities
Topographic Topographic reliefrelief is is the change in elevation the change in elevation between the highest between the highest and the lowest placesand the lowest places
Landscape RegionsLandscape Regions MountainMountain landscapes have the greatest landscapes have the greatest
relief between the highest peaks and the relief between the highest peaks and the deepest valleysdeepest valleys
A great variety of rock types are commonA great variety of rock types are common Mountains are common where converging Mountains are common where converging
tectonic plates collidetectonic plates collide Stream gradients are Stream gradients are
high, and the fast high, and the fast moving streams quickly moving streams quickly erode deep valleys erode deep valleys between the between the mountain peaksmountain peaks
Landscape RegionsLandscape Regions PlateauPlateau landscapes are relatively flat landscapes are relatively flat
or rolling uplands where streams have or rolling uplands where streams have cut deep valleyscut deep valleys
Commonly underlain by flat layers of Commonly underlain by flat layers of sedimentary rocksedimentary rock
Less topographic Less topographic relief than mountains relief than mountains but more relief than but more relief than the plainsthe plains
Landscape RegionsLandscape Regions
PlainsPlains have the least topographic have the least topographic reliefrelief
They may contain a few small hills, They may contain a few small hills, but are generally flat and at low but are generally flat and at low elevationelevation
Commonly underlain by flat layers of Commonly underlain by flat layers of sedimentary rocksedimentary rock
Climate Influence on Climate Influence on RegionsRegions
Moist, Moist, HumidHumid climates usually have climates usually have rounded landscapesrounded landscapes
Slopes are not as steep because moist Slopes are not as steep because moist climates promote a protective cover of climates promote a protective cover of vegetationvegetation Plants cover protects the soil Plants cover protects the soil
from rapid runoff and erosionfrom rapid runoff and erosion
Climate Influence on Climate Influence on RegionsRegions
AridArid (dry) climates usually produce (dry) climates usually produce thin soils with little humusthin soils with little humus
With little plant cover to protect the With little plant cover to protect the soil, sediment is carried away during soil, sediment is carried away during rainfallrainfall Large areas of exposed bedrock and Large areas of exposed bedrock and
steep rock faces are the resultsteep rock faces are the result
Landscape Regions of the Landscape Regions of the USUS
Landscape Regions of NYLandscape Regions of NY
Drainage PatternsDrainage Patterns Harder rocks will form hills and ridgesHarder rocks will form hills and ridges Erosion of the weaker rock will make Erosion of the weaker rock will make
the major valleysthe major valleys Streams will tend to follow zones of Streams will tend to follow zones of
weaker rock and flow downhillweaker rock and flow downhill
Drainage PatternsDrainage Patterns
Human Activities Human Activities Can Affect LandscapesCan Affect Landscapes
Farming and construction projects can Farming and construction projects can accelerate erosion and effect accelerate erosion and effect landscape developmentlandscape development
Farmers and engineers must be Farmers and engineers must be guided in planning their projects by guided in planning their projects by appropriate conservation practicesappropriate conservation practices