Weathering and Erosion. Objectives Identify the cause of rock shaping due to weathering and erosion Explain how chemical weather forms caves Describe.

Weathering and Erosion Weathering and Erosion

ObjectivesObjectives Identify the cause of rock shaping due to Identify the cause of rock shaping due to

weathering and erosionweathering and erosion Explain how chemical weather forms Explain how chemical weather forms

cavescaves Describe how acid rain affects the Describe how acid rain affects the

landscapelandscape

Two Types of WeatheringTwo Types of Weathering

Physical or Mechanical – breaking rock Physical or Mechanical – breaking rock into smaller piecesinto smaller pieces

Chemical – breaks down the rock into Chemical – breaks down the rock into something elsesomething else

Ice can break RocksIce can break Rocks

When water freezes it expands and gets When water freezes it expands and gets less dense (this is why ice cubes float)less dense (this is why ice cubes float)

Frost WedgingFrost Wedging is when water enters a is when water enters a crack in a rock, freezes and expands, and crack in a rock, freezes and expands, and pushes the rock apartpushes the rock apart

Frost wedging is why there are more rocks Frost wedging is why there are more rocks on the roads next to cliffs after winter on the roads next to cliffs after winter monthsmonths

Example of Frost WedgingExample of Frost Wedging

Frost Frost wedging wedging has broken has broken the rock the rock into layers into layers and and pushed pushed them in them in many many directionsdirections

Plant roots break rocksPlant roots break rocks

Plant roots enter a crack when they are Plant roots enter a crack when they are smallsmall

As they grow, they expand and crack the As they grow, they expand and crack the rockrock

Bryce Canyon National ParkBryce Canyon National Park

HooDoos Form In Bryce CanyonHooDoos Form In Bryce Canyon

The HooDoos form from a combination of The HooDoos form from a combination of Frost Wedging and Chemical WeatheringFrost Wedging and Chemical Weathering

200 days a year, the temperature in Bryce 200 days a year, the temperature in Bryce Canyon fluctuates both above freezing Canyon fluctuates both above freezing and below freezingand below freezing

That’s 200 days a year for frost wedging to That’s 200 days a year for frost wedging to occuroccur

The chemical weathering is both oxygen The chemical weathering is both oxygen and acid rainand acid rain

HooDoos in Bryce CanyonHooDoos in Bryce Canyon

Arches National ParkArches National Park

Arches also form from Frost Wedging, Arches also form from Frost Wedging, wind erosion, and Chemical Weatheringwind erosion, and Chemical Weathering

Fins form when cracks in Fins form when cracks in sandstone are erodedsandstone are eroded

Double Arch has been used in Double Arch has been used in movies (Raiders of the Lost Arc)movies (Raiders of the Lost Arc)

Weathering continues on fins, Weathering continues on fins, some fins collapse, others form some fins collapse, others form

spires and archesspires and arches

Glaciers also erode rocksGlaciers also erode rocks

Glaciers are large rivers of iceGlaciers are large rivers of ice They flow, slowly, down slopesThey flow, slowly, down slopes As they flow, they carve the rocks As they flow, they carve the rocks

underneath them and take large amounts underneath them and take large amounts of rocks and boulders with them as they of rocks and boulders with them as they movemove

They also grind some of the rocks into They also grind some of the rocks into small particles called small particles called Glacial SiltGlacial Silt

Yosemite ValleyYosemite Valley

Glacial SiltGlacial Silt

Glacial silt is common Glacial silt is common in Alaska and in Alaska and extremely dangerousextremely dangerous

Tourists walk out onto Tourists walk out onto the beaches of the beaches of Alaska, only to realize Alaska, only to realize it is like quicksandit is like quicksand

They get stuck and They get stuck and the tide comes inthe tide comes in

Glacial SiltGlacial Silt

The murky The murky looking looking water is water is caused by caused by fine Glacial fine Glacial silt floating silt floating in the waterin the water

Lake Louise, CanadaLake Louise, CanadaThe water color is from Glacial SiltThe water color is from Glacial Silt

Yosemite Valley Yosemite Valley

Yosemite is formed from mostly GraniteYosemite is formed from mostly Granite Granite takes longer to erode than the Granite takes longer to erode than the

sandstone of Bryce Canyon and Arches sandstone of Bryce Canyon and Arches National ParkNational Park

The major shapes in Yosemite were The major shapes in Yosemite were weathered by Glaciers moving through the weathered by Glaciers moving through the valleyvalley

Frost Wedging does still occur todayFrost Wedging does still occur today

Half Dome was cut by a GlacierHalf Dome was cut by a Glacier

Chemical WeatheringChemical Weathering

Things as basic as Oxygen, Carbon Things as basic as Oxygen, Carbon Dioxide, and acid cause chemical changes Dioxide, and acid cause chemical changes in rocksin rocks

OxidationOxidation

Oxygen is a very reactive elementOxygen is a very reactive element Oxygen combines with many elementsOxygen combines with many elements The Red Rocks seen around the Rocky The Red Rocks seen around the Rocky

Mountains (Grand Junction, New Mexico..) Mountains (Grand Junction, New Mexico..) are Hematiteare Hematite

Hematite forms when iron reacts with Hematite forms when iron reacts with oxygenoxygen

The red color is an indication of old rocks The red color is an indication of old rocks and old soilsand old soils

Grand Junction, ColoradoGrand Junction, Colorado

Chemical Weathering Chemical Weathering by Carbon Dioxideby Carbon Dioxide

Carbon Dioxide gets dissolved in rainwaterCarbon Dioxide gets dissolved in rainwater Carbonic Acid, HCarbonic Acid, H22COCO33

Although this is a weak acid, it is strong Although this is a weak acid, it is strong enough to weather rocks both above enough to weather rocks both above ground (acid rain) and below ground ground (acid rain) and below ground (caves)(caves)

Cave FormationsCave Formations

We talked about cave formation yesterdayWe talked about cave formation yesterday Caves are usually in limestoneCaves are usually in limestone Limestone reacts with Carbonic Acid in the Limestone reacts with Carbonic Acid in the

water and “dissolves” and is carried awaywater and “dissolves” and is carried away

pH measures acidpH measures acid

Neutral water has a pH of 7.0 and has the same Neutral water has a pH of 7.0 and has the same amount of hydrogen ions (Hamount of hydrogen ions (H++) as hydroxide ions ) as hydroxide ions (OH(OH--))

Hydrogen ions are acidicHydrogen ions are acidic Hydroxide ions are basicHydroxide ions are basic Many things you drink are acidic (they can cause Many things you drink are acidic (they can cause

damage to your insides) like Coffee, Soft drinks, damage to your insides) like Coffee, Soft drinks, Orange JuiceOrange Juice

Milk is a basic drink (does not cause damage)Milk is a basic drink (does not cause damage)

AcidsAcids

Numbers below 7 are acidicNumbers below 7 are acidic Lower numbers are more acidicLower numbers are more acidic Coffee and many soft drinks have pHs Coffee and many soft drinks have pHs

around 2-3, they are very acidic, they eat around 2-3, they are very acidic, they eat the enamel of you teeththe enamel of you teeth

BasesBases

pHs above 7 are considered BasespHs above 7 are considered Bases These do not have the reactive hydrogen These do not have the reactive hydrogen

ions in them and do not cause damage ions in them and do not cause damage like acids dolike acids do

There is research that indicated many There is research that indicated many diseases could be prevented or reversed if diseases could be prevented or reversed if our bodies pH were kept more basic, this our bodies pH were kept more basic, this includes cancer and many virusesincludes cancer and many viruses

Mountain Dew MouthMountain Dew Mouth

It’s acidic dudeIt’s acidic dude This person is 15!This person is 15!

Acid RainAcid Rain

Rain water is naturally acidic in many parts Rain water is naturally acidic in many parts of the countryof the country

Rain water below a pH of 5.7 is acidic Rain water below a pH of 5.7 is acidic enough to damage forests, streams, living enough to damage forests, streams, living organisms, and rocksorganisms, and rocks

Because humans continue to burn fossil Because humans continue to burn fossil fuel, our rain is becoming more acidicfuel, our rain is becoming more acidic

Fossil fuel increases the amount of Nitrous Fossil fuel increases the amount of Nitrous acid and sulfuric acid in our rain wateracid and sulfuric acid in our rain water

Coal Fired plants release Coal Fired plants release nitrogen and sulfur dioxidenitrogen and sulfur dioxide

Effect of acid rain on forestsEffect of acid rain on forests

Effect of acid rain on statuesEffect of acid rain on statuesThese are not old statuesThese are not old statues

ErosionErosion

Erosion is the removal and transport of Erosion is the removal and transport of weathered and non-weathered materialweathered and non-weathered material

Can be from running water, wind, waves, Can be from running water, wind, waves, ice, gravityice, gravity

Water is the most effective agent of Water is the most effective agent of weathering and erosion (we’ve already weathering and erosion (we’ve already discussed glaciers, cave formation, acid discussed glaciers, cave formation, acid rain)rain)

Streams move more than waterStreams move more than water

Have you seen the Rio Grande in Spring?Have you seen the Rio Grande in Spring? It’s muddy, it’s carrying with it soil, rock, It’s muddy, it’s carrying with it soil, rock,

and organic material (leaves, branches, and organic material (leaves, branches, dead animals…)dead animals…)

Streams can carry material when they are Streams can carry material when they are moving fastmoving fast

When water slows down, it drops much of When water slows down, it drops much of what it was carryingwhat it was carrying

DepositionDeposition

Sediment Sediment is laid is laid downdown

Rocky Mountain National Park Rocky Mountain National Park Water flowing down steep hill Water flowing down steep hill slowed and deposited mudslowed and deposited mud

Ocean’s move sedimentsOcean’s move sediments

Wave actionWave action - Ocean waves can erode - Ocean waves can erode coastline. In many areas where people coastline. In many areas where people own coastline, they can lose property to own coastline, they can lose property to the ocean.the ocean.

You can lose 40 feet in one stormYou can lose 40 feet in one storm

The coastline is erodingThe coastline is eroding

Erosion removes sand from beachesErosion removes sand from beaches Waves erode beachesWaves erode beaches Miami Beach is losing beachfront property every Miami Beach is losing beachfront property every

yearyear Cape Cod, Mass. Also loses beachfront property Cape Cod, Mass. Also loses beachfront property

– some people have to move their houses so the – some people have to move their houses so the house is protected from the eroding coastlinehouse is protected from the eroding coastline

Things Things communities do communities do

to save their to save their beachesbeaches

Build retaining wallsBuild retaining walls Bull dose more sand in Bull dose more sand in

to beachesto beaches