Geology of National ParksGeology of National ParksGeology of National ParksGeology of National ParksYosemiteYosemiteYosemiteYosemite

Grand CanyonGrand CanyonGrand CanyonGrand Canyon

Bryce CanyonBryce CanyonBryce CanyonBryce Canyon

LassenLassen Peak VolcanicPeak VolcanicLassenLassen Peak VolcanicPeak Volcanic

YellowstoneYellowstoneYellowstoneYellowstoneInstructor:Instructor:Jack PierceJack PierceInstructor:Instructor:Jack PierceJack Pierce

Geology of National Parks OverviewGeology of National Parks OverviewGeology of National Parks OverviewGeology of National Parks Overview

““More than a Park Ranger Discussion of National Parks”More than a Park Ranger Discussion of National Parks” This class surveys basic geologic principles which include theThis class surveys basic geologic principles which include the

physical and historical geological characteristics of each physical and historical geological characteristics of each national park. national park.

Hands-on examples of various rock types will be presented forHands-on examples of various rock types will be presented foreach national park.each national park.

Discussion will include various geological interest points withinDiscussion will include various geological interest points withineach national park.each national park.

““More than a Park Ranger Discussion of National Parks”More than a Park Ranger Discussion of National Parks” This class surveys basic geologic principles which include theThis class surveys basic geologic principles which include the

physical and historical geological characteristics of each physical and historical geological characteristics of each national park. national park.

Hands-on examples of various rock types will be presented forHands-on examples of various rock types will be presented foreach national park.each national park.

Discussion will include various geological interest points withinDiscussion will include various geological interest points withineach national park.each national park.

National Park Geologic BackgroundNational Park Geologic Background

• The Rock CycleThe Rock Cycle - - Igneous, Sedimentary, Metamorphic Rocks Igneous, Sedimentary, Metamorphic Rocks • Plate Tectonic OverviewPlate Tectonic Overview• The Geologic Time ScaleThe Geologic Time Scale

The Rock CycleThe Rock Cycle

Plate TectonicsPlate Tectonics

Geologic Time ScaleGeologic Time Scale

Alfred Wegener – German Meteorologist – geophysicistAlfred Wegener – German Meteorologist – geophysicist

•Proposed that continents drift - observed Africa and South America Proposed that continents drift - observed Africa and South America (middle 1920’s)(middle 1920’s)

•Proposed the super-continent Pangaea Proposed the super-continent Pangaea

•Found evidence to support his hypothesis of Continental DriftFound evidence to support his hypothesis of Continental Drift•fossil evidence, rock and climate correlationsfossil evidence, rock and climate correlations

Alfred WegenerAlfred WegenerAlfred WegenerAlfred Wegener

• Continental Drift hypothesis was NOT accepted --- Wegener the Continental Drift hypothesis was NOT accepted --- Wegener the laughing stalk of the science world laughing stalk of the science world

• Could not answer Could not answer HOWHOW the continents move the continents move

PangaeaPangaea

MagmaMagmaMagmaMagma

Magma rises from the mantle “spreading apart” and Magma rises from the mantle “spreading apart” and creates new ocean floor – discovered in the 1960’screates new ocean floor – discovered in the 1960’sMagma rises from the mantle “spreading apart” and Magma rises from the mantle “spreading apart” and creates new ocean floor – discovered in the 1960’screates new ocean floor – discovered in the 1960’s

Youngest ocean floorYoungest ocean floorYoungest ocean floorYoungest ocean flooroldestoldestocean floorocean floor

oldestoldestocean floorocean floor

oldestoldestocean floorocean floor

oldestoldestocean floorocean floor

MantleMantleMantleMantle MantleMantleMantleMantle

Seafloor spreadingSeafloor spreadingSeafloor spreadingSeafloor spreading

The Theory of Plate TectonicsThe Theory of Plate Tectonics

solid rigid lithospheric plates riding along a “plastic”(hot wax) material called the asthenospheresolid rigid lithospheric plates riding along a “plastic”(hot wax) material called the asthenosphere

continental and ocean floor materialcontinental and ocean floor material

upper mantleupper mantlelithospherelithosphere

Asthenosphere – hot mantle rock that behaves like “hot wax”Asthenosphere – hot mantle rock that behaves like “hot wax”

lithospherelithospherelithospherelithosphere

AsthenosphereAsthenosphere

AfricaAfrica

PlatePlate

Continents Ride on PlatesContinents Ride on Plates

Divergent Boundary:Divergent Boundary:• new ocean floor is produced (2-3 cm/yr)new ocean floor is produced (2-3 cm/yr)• ocean floor “grows” equally on both ocean floor “grows” equally on both sides of the ridge’sides of the ridge’• Example: Mid-Atlantic RidgeExample: Mid-Atlantic Ridge

3-Types of Plate Boundaries3-Types of Plate Boundaries• plates move relative to one anotherplates move relative to one another• all major interactions of deformation occur at plate boundariesall major interactions of deformation occur at plate boundaries• most volcanic and EQ activities occur at plate boundariesmost volcanic and EQ activities occur at plate boundaries

Ocean-ContOcean-Cont Ocean-OceanOcean-Ocean Cont-ContCont-Cont

Convergent BoundariesConvergent Boundaries

Transform Boundary• plates slide past one another• common on the ocean floor• Example: San Andreas Fault

The Geologic Time Scale:The Geologic Time Scale:

• Created during the nineteenth century in WesternCreated during the nineteenth century in Western Europe and Great BritainEurope and Great Britain

• Sub-divides the 4.6 billion-year history of the earthSub-divides the 4.6 billion-year history of the earth

• EonsEonsErasEras

PeriodsPeriodsEpochsEpochs

LargerLargerTime FrameTime Frame

SmallerSmallerTime FrameTime Frame

Age of Reptiles

Amphibians

Age of fish

Invertebrates

Yosemite National ParkYosemite National ParkEstablished in 1890Established in 1890

YosemiteYosemiteNational National

ParkPark

Yosemite ValleyYosemite Valley

California

Intrusive Igneous Rocks of YosemiteIntrusive Igneous Rocks of YosemiteIntrusive Igneous Rocks of YosemiteIntrusive Igneous Rocks of Yosemite• Magma cools below the surfaceMagma cools below the surface

• Magma cools slowlyMagma cools slowly

• Visible mineral grainsVisible mineral grains• quartz, orthoclase, plagioclase, hornblende,quartz, orthoclase, plagioclase, hornblende, biotitebiotite

• Various forms of graniteVarious forms of granite• granodiorite, tonalite, quartz-monzonitegranodiorite, tonalite, quartz-monzonite

NEVER TAKE GRANITE FOR GRANITE !NEVER TAKE GRANITE FOR GRANITE !

K, Al, Na, Ca, SiO2

increasing Fe, Mgincreasing Fe, Mgdecreasing SiOdecreasing SiO22

GabbroGabbroDioriteDiorite

Ocean to Continent ConvergenceOcean to Continent Convergence

A

D. formation of composite volcanoes (explosive) on the continent

D. formation of composite volcanoes (explosive) on the continent

BC

DA. convergence of platesA. convergence of plates

B. subduction of oceanic plate materialB. subduction of oceanic plate material

C. oceanic plate melts and less dense magma rises

C. oceanic plate melts and less dense magma rises

How did the granite form to produce Yosemite?How did the granite form to produce Yosemite?The Yosemite Tectonic SettingThe Yosemite Tectonic Setting

How did the granite form to produce Yosemite?How did the granite form to produce Yosemite?The Yosemite Tectonic SettingThe Yosemite Tectonic Setting

YosemiteYosemiteGraniteGranite

El CapitanEl CapitanMonolithMonolith

Half DomeHalf Dome

Cathedral RocksCathedral Rocks

Quartz MonzoniteQuartz Monzonite

granitegranite

granitegranite

Layered sediments covered the sea floor west of the North American continent.

470-220 m.y.

The land continued to push up, the water continued to erode down. The V-shaped valley got deeper.

220-80 m.y.

Uplift and erosion stripped away most of the sedimentary layers, leaving the cooled magma (granite) exposed.

80-25 m.y.

The mountains were pushed up higher from an increase in activity below the earth’s surface, causing the Merced river to dig deeper (erode) into its valley.

25-2 m.y.

An ice age occurred. Glaciers from the highest An ice age occurred. Glaciers from the highest parts of the Sierra Nevada grew so big that they parts of the Sierra Nevada grew so big that they flowed down through Yosemite Valley, widening flowed down through Yosemite Valley, widening and cutting the Merced river’s path. and cutting the Merced river’s path.

The glaciers melted out of Yosemite ValleyThe glaciers melted out of Yosemite Valley.

The sediment eventually filled Lake Yosemite and The sediment eventually filled Lake Yosemite and turned it into the meadows and forests of today. turned it into the meadows and forests of today.

2 m.y.

10,000 yrs

Today

Geologic Forces that Shaped Present Day Geologic Forces that Shaped Present Day Yosemite National ParkYosemite National Park

Geologic Forces that Shaped Present Day Geologic Forces that Shaped Present Day Yosemite National ParkYosemite National Park

Glacial ProcessesGlacial Processes• Strong erosive glacial forces produce the striking topographyStrong erosive glacial forces produce the striking topography

observed today throughout Yosemite Valleyobserved today throughout Yosemite Valley

Weathering and Mass Wasting ProcessesWeathering and Mass Wasting Processes• Physical / Chemical processes work 24/7 to reduce Physical / Chemical processes work 24/7 to reduce topography of the Yosemite Valleytopography of the Yosemite Valley

• Mass wasting processes involve the down-slope movementMass wasting processes involve the down-slope movement of weathered material under the influence of gravityof weathered material under the influence of gravity

Glacial ProcessesGlacial Processes

Alpine (valley) glaciationAlpine (valley) glaciation Continental glaciationContinental glaciation

•Exists in high mountainous areasExists in high mountainous areas

•Occupies pre-existing river valleysOccupies pre-existing river valleys

•Typically bounded by steep Typically bounded by steep mountain walls mountain walls

•Typically, lengths are longer thanTypically, lengths are longer than widthwidth

•Extensively covers continentsExtensively covers continents

•Greenland, AntarcticaGreenland, Antarctica

•Flat broad large ice sheetsFlat broad large ice sheets

YosemiteYosemite Great Lakes U.S.Great Lakes U.S.

Evidence of past glacial activity in Yosemite – What do glaciers leave behind?Evidence of past glacial activity in Yosemite – What do glaciers leave behind?

Glacial Erosion – the forces of glacial activity

River valleys before River valleys before glaciation (note the “V” glaciation (note the “V” shape valleys)shape valleys)

Glaciation takes place and Glaciation takes place and invades the “V” shape invades the “V” shape valleysvalleys

Erosional features left afterErosional features left afterglaciation creating variousglaciation creating variouserosion featureserosion features

U-shaped valleyU-shaped valley hornshorns cirquescirques areatesareates glacial morainesglacial moraines hanging valleyshanging valleys

Glacial Erosion – Glacial landforms from erosionGlacial Erosion – Glacial landforms from erosion

Frost wedging

Ice body moves across bedrockIce body moves across bedrockfracturing rock material.fracturing rock material.

Frost wedging processes migrateFrost wedging processes migratethrough cracks and rock material through cracks and rock material is plucked out on the low pressureis plucked out on the low pressureside.side.

Plucking processesPlucking processes

Abrasion processesAbrasion processes

Rock material embedded withinRock material embedded withinthe glacier moves along the surfacethe glacier moves along the surfaceand scratches, scours and producesand scratches, scours and producesgrooves and striations grooves and striations

Acts like sandpaper and “polishes”Acts like sandpaper and “polishes”the rock surface. the rock surface.

Can you see the U-shaped valley? Can you see the U-shaped valley? Can you see the hanging valley?Can you see the hanging valley?YosemiteYosemite

Yosemite Region

Yosemite Valle

y

Glacial moraines: Layers of “rock debris” (piles of rock) left over from an Glacial moraines: Layers of “rock debris” (piles of rock) left over from an advancing / retreating glacieradvancing / retreating glacier

Tuolumne MeadowsTuolumne Meadows(lateral moraine)(lateral moraine)

Base of Half DomeBase of Half Dome(medial moraine)(medial moraine)

Beginning of YosemiteBeginning of YosemiteValley – terminal moraine Valley – terminal moraine

Erosional features (landforms) of Erosional features (landforms) of AlpineAlpine glaciation glaciation

Roches MoutonneesRoches Moutonnees elongated hills that appear to beelongated hills that appear to be asymmetrical bedrock knobs thatasymmetrical bedrock knobs that protrude upwards from the bedrockprotrude upwards from the bedrock

Direction of glacierDirection of glacier

Glacier moves over resistant bedrockGlacier moves over resistant bedrockproducing a gentle slope and pluckingproducing a gentle slope and pluckingof debris steepens the opposite sideof debris steepens the opposite side

pluckingplucking

Direction of glacierDirection of glacier

pluckingplucking

Lembert Dome - Yosemite

flow direction of glacierflow direction of glacier

How did this boulder get here?How did this boulder get here?

ErraticErratic• “ “huge” rock fragments “floating” in the moving glacierhuge” rock fragments “floating” in the moving glacier• glacier melts and literally dropsglacier melts and literally drops and the boulder settles to and the boulder settles to the ground.the ground.

Yosemite ErraticYosemite ErraticYosemite ErraticYosemite Erratic

Rocks can be Rocks can be broken downbroken down or or chemically alteredchemically altered on the on theearth’s surface.earth’s surface.

Mechanical WeatheringMechanical Weathering: : Rocks are physically broken down by variousRocks are physically broken down by varioussurface processes into smaller parts withoutsurface processes into smaller parts withoutchanging physical properties. changing physical properties.

Chemical WeatheringChemical Weathering: : Rocks are altered from one form to a Rocks are altered from one form to a

completely new form with a different completely new form with a different set of physical properties.set of physical properties.

Weathering Processes at YosemiteWeathering Processes at YosemiteWeathering Processes at YosemiteWeathering Processes at Yosemite

Frost WedgingFrost WedgingFrost WedgingFrost Wedging

• Repeated cycles of freezing Repeated cycles of freezing and thawing.and thawing.

• Ice expands 9% of its volume.Ice expands 9% of its volume.

• Rock is continually broken Rock is continually broken down over geologic timedown over geologic time

• Part of the Yosemite Part of the Yosemite weathering cycle.weathering cycle.

• Repeated cycles of freezing Repeated cycles of freezing and thawing.and thawing.

• Ice expands 9% of its volume.Ice expands 9% of its volume.

• Rock is continually broken Rock is continually broken down over geologic timedown over geologic time

• Part of the Yosemite Part of the Yosemite weathering cycle.weathering cycle.

Yosemite WeatheringYosemite WeatheringYosemite WeatheringYosemite Weathering

Frost WedgingFrost Wedging – rocks are broken into – rocks are broken intoplates and split apart.plates and split apart.Frost WedgingFrost Wedging – rocks are broken into – rocks are broken intoplates and split apart.plates and split apart.

Yosemite Frost WedgingYosemite Frost WedgingYosemite Frost WedgingYosemite Frost Wedging

ExfoliationExfoliation

• unloading of overlying rock material releases pressure

• expansion of granitic bodies causing “sheeting” or slabbing granite

• granite “sheets” break along planes of weakness or joints

• exacerbated by frost wedging

• dominant weathering force in Yosemite

• unloading of overlying rock material releases pressure

• expansion of granitic bodies causing “sheeting” or slabbing granite

• granite “sheets” break along planes of weakness or joints

• exacerbated by frost wedging

• dominant weathering force in Yosemite

Exfoliation DomeExfoliation Dome – granite is – granite is ““sheeting” from loss of pressure duesheeting” from loss of pressure due to unloading processes.to unloading processes.

Exfoliation DomeExfoliation Dome – granite is – granite is ““sheeting” from loss of pressure duesheeting” from loss of pressure due to unloading processes.to unloading processes.

Exfoliation at Half DomeExfoliation at Half DomeExfoliation at Half DomeExfoliation at Half Dome

Royal Arches - ExfoliationRoyal Arches - ExfoliationRoyal Arches - ExfoliationRoyal Arches - Exfoliation Yosemite ExfoliationYosemite ExfoliationYosemite ExfoliationYosemite Exfoliation

Tunnel to viewTunnel to viewthe U-shaped Valleythe U-shaped Valley

Tunnel to viewTunnel to viewthe U-shaped Valleythe U-shaped Valley

Lembert DomeLembert DomeLembert DomeLembert Dome