Geologic Processes

7/30/2019 Geologic Processes

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Geologic

ProcessesNotes

The study ofdynamic processesoccurring on theearths surface & in

its interior. As primitive earth

cooled over eons, itsinterior separatedinto 3 concentriczones: the core, themantle, & the crust.

What is geology?

CORE

Earths innermost zone.

Extremely hot.

Has a solid inner core believedto consist of an iron-nickel alloysurrounded by an outer liquidcore of molten material (magma

= molten rock).

MANTLE

A thick zone surrounding thecore.

Most of it is solid rockthe rigidoutermost part.

Contains the asthenosphere: azone of hot, partly melted rockthat flows; can be deformed likesoft plastic.

CRUST

Outermost and thinnest zone.

Consists of:

continental crust: lies beneath thecontinents including the continentalshelves extending into the oceans.

oceanic crust: underlies the oceanbasins and makes up 71% of theearths crust.

Volcanoes Folded

mountain beltAbyssal

floor

Oceanic

ridgeAbyssal

floor Trench Ab

p

Abyssal hills Craton

Oceanic crust(lithosphere)

Continental

shelf Contineslope

ContinenriseMantle

(lithosphere) Continental crust (lithosphere)

Mantle (lithosphere)

Mantle

(asthenosphere)

Major features of the earths crust & upper mantl

The lithosphere, composed of the crust & outermomantle, is rigid & brittle.

The asthenosphere(zone in the mantle) can bedeformed by heat and pressure.


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The earth beneath your feetis moving.

Convections cells or currents:move large volumes of rock & heat

in loops within the mantle likegigantic conveyer belts. These flows of energy & heated

materials cause huge rigid plates tomove slowly on top of the densermantle.

Spreading center

Ocean

trench

Subduction

zone Oceanic crust Oceanic crust

Continentalcrust

Continent

Material coolsas it reaches

the outer

mantle

Cold densematerial fallsback through

mantle

Hot material

rising

through the

mantle

Mantle

convectioncell

Two plates movetowards each other.One is subducted backinto the mantle on a

falling convectioncurrent.

Mantl

Hot outercore

Innercore

The earthscrust is madeup of amosaic ofhuge rigidplates, called

tectonicplates, whichmove veryslowly acrosstheasthenospherein response toforces in themantle.

TECTONIC PLATES Gigantic rigid plates.

Composed of the continental &oceanic crust and the rigidoutermost part of the mantle:the lithosphere.

Worlds largest & slowest-movingsurfboards. Their typical speed is about the

rate at which fingernails grow.

TECTONICPLATES

You ride on one of these plates your wholife without noticing!!!

Throughout earths 4.6 billion year

history, continents have split apart &joined as tectonic plates drifted 1,000s kilometers back & forth atop the mantle

135 million years ago

Present65 million years ago

225 million years ago

Rock & fossil evidence indicates that 200-250million yrs ago, all continents were locked together

in a super continentPangaea.

About 180 million yrs ago, Pangaea began splitting apartas tectonic plates separated, eventually resulting in

todays locations of the continents.

Most geologic activity takes placat the boundaries between plateas they separate, collide, or slid

past one another.

This causes:

Mountains & oceanic trenches to for

Earthquakes to shake parts of thecrust.

Volcanoes to erupt.

Continents to form or separate.


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The Earths Major Tectonic Plates:What plate are you riding on?

The extremely slow movements of theseplates cause them to grind into oneanother at convergent plate boundariesmove apart from one another at diverge

plate boundaries, and slide past eachother at transform plate boundaries.

Trench Volcanic island arc Craton

Transform

fault

Lithosphere

Lithosphere Lithosphere

Asthenosphere Asthenosphere Asthenosph

Divergent plate boundaries Convergent plate boundaries Transform faults

Rising

magma

When oceanic plates move apart inopposite directions & magma flows upthrough the resulting cracks.

Creates oceanic ridges where somehave higher peaks & deeper canyonsthan the continents have.

Divergent Plates When an oceanic plate collides with acontinental plate. The continental plate rides up over the

denser oceanic plate & pushes it down intothe mantle in a process called subduction.

Over time, the subducted plate melts & thrises again to the earths surface as magm

A trench forms at the boundary between t2 converging plates.

Convergent Plates

When 2 continents carried onconverging plates ram into eachother, they push up mountainranges, such as the Himalayas, alongthe collision boundary.

The Himalayanmountain range

b/w China &India includes

Mount Everest,the worlds

highestmountain peak.

Convergent Plates

When plates slide & grind past one anothalong a fracture (fault) in the lithospher

Most are located on the ocean floor, butfew are found on land.

The North American Plate & the Pacific Plateslide past each other along Californias SanAndreas fault.

Transform Faults(opposite but parallel

directions)


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Transform Fault PlateBoundaries

The San AndreasFault, which runs

along almost the fulllength of CA, isresponsible forearthquakes of

various magnitudes.

Importance of Geologic Processe Plate movement adds new land at

boundaries and produces mountains,trenches, earthquakes, and volcanoes.

Tectonic plate movement plays a big

part in the recycling of the planetscrust over geological time, which hashelped form mineral deposits & promoand sustain life.

As continents separated, populationsbecame geographically & reproductiveisolated, and speciation occurred.

Plate movements & volcanic eruptionshave led to climate change that shiftedwildlife habitats, wiped out largenumbers of species, & createdopportunities for the evolution of newspecies. The locations of continents and oceanic

basins influence climate.

The movement of continents haveallowed species to move.

Importance of Geologic Processes SPECIATION

New species can arise whenmembers of a population becomeisolated for a long period of time Their genetic makeup changes,

preventing them from producingfertile offspring with the original

population; they become twodifferent sets of species.

Geographic Isolation

can lead to reproductive isolation,divergence of gene pools, andspeciation.

Southern

population

Early foxpopulation

Spreads northand southand separates

Northernpopulation

Adapted to heatthrough lightweightfur and long ears,legs, and nose,

which give off moreheat.

Different environmentalconditions lead to differentselective pressures and evolution

into two different species.

Arctic Fox: Adapted to coldthrough heavier fur,short ears, short legs,

and short nose. Whitefur matches snow forcamouflage.

Gray Fox:

Some parts of the earths surface buup & some wear down.

Internal geologic processes: generated heat from earths interior, typically builup the earths surface in the form ofcontinental & oceanic crust.

External geologic processes: driven byenergy from the sun (mostly in the formof flowing water and wind) & influenced gravity; tend to wear down the earthssurface & move matter from one place tanother.


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External Geologic Processes Weathering:physical, chemical, & biological

processes that break down rocks into smallerparticles that help build soil.

Erosion: material is dissolved, loosened, orworn away from one part of the earthssurface & deposited elsewhere. Flowing streams & rain cause most erosion. Wind also blows particles of soil from one area

to another. Human activitiesthose that destroy vegetation

that holds soil in placeaccelerate the process. Glaciers (slowly flowing bodies of ice) cause

erosion.

Glaciers

Rock is pulled along or plucked out of theland surface. During the last ice age (ended 10,000 years ag

ice sheets covered vast areas of North AmeriEurope, & Asia.

The Great Lakes formed during this period asretreating glaciers gouged (hollowed) out hugebasins, & as the climate warmed, the glaciersmelted filling in these depressions.

Move slowly down amountainside or over a widearea under the influence ofgravity.

ParentMaterial

(rock)

Biologicalweathering(tree rootsand lichens)

Chemicalweathering(water, acids,& gases)

Physicalweathering(wind, rain,thermalexpansion &contraction,water freezing)

Particles of parent material

Biological, chemical, & physical processes weather orconvert rock into smaller fragments & particles; the1st step in soil formation.

Replacement of abiologically diversetemperate grasslandwith a monoculturecrop in California.

When humans removethe tangled rootnetwork of naturalgrasses, the fertiletopsoil becomessubject to severe wind

erosion unless it iscovered with sometype of vegetation.

Severe gully erosion ocropland in Bolivia.

Tropical deforestation in Thailand. The clearing of trees that absorb carbon

dioxide increases global warming. It also dehydrates the soil by exposing it to

sunlight. The dry topsoil blows away, which prevents the

reestablishment of a forest in this area.

PacificPlate

Largest plate off the coast of CA. Volcanoes & earthquakes occur he Location of the Ring of Fire.


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ACTIVE VOLCANOES Where magma reaches earths surface

(lava) through a fissure (central vent).

Forms when one tectonic plate slidesunder or moves away from another

plate. Releases debris into the environment:

lava rock, ash, liquid lava, & gases(water vapor, carbon dioxide, & sulfurdioxide).

Concentrated along plate boundaries.

Extinct

volcanoes

Eruption cloud

AshAsh flow

Lava flow

Mud flow

Landslide Central ve

Magma co

Magma re

Acid

Chains ofislands havebeen createdby volcanoesthat eruptedand thenbecameinactive.

Mount Pinatubo: cooled the planet

Largest volcanic eruption during20th century; occurred in 1991.

Killed several hundred people in thePhilippines.

Ejected enough material into theatmosphere to reduce incoming

solar energy & cool the earthsaverage temperature for 15 months!

MountPinatubo

http://videos.howstuffworks.com/discovery/71-1991-mount-pinatubo-erruption-video.htm

Mount St. Helens, WA Worst volcanic disaster

in U.S. history.

Erupted May 18, 1980. 57 people & large #s of

wildlife were killed.

Large areas of forestswere obliterated. Ecological succession has

restored some vegetation.

Benefits of Volcanic Activity

Creates outstanding scenery.

Majestic mountains

Some lakes (Crater Lake in OR)

Highly fertile soils are produceby the weathering of lava.


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The collapse of Mt. Mazama created Crater Lake.

To reduce loss of human life

Use historical records & geologicmeasurements to identify high-ris

areas. Use monitoring devices that warn

when volcanoes are likely to erupt

Develop evacuation plans forvolcanic-prone areas.

EARTHQUAKES Forces inside the mantle & along the

surface push, deform, & stress rocks.

When a fault forms, or when there isabrupt movement on an existing fault,energy that has accumulated is releasedin the form of vibrations = seismicwaves.

Seismic waves move in all directionsthrough the surrounding rock.

EARTHQUAKES

Most occur at boundaries of tectonicplates.

Effects include shaking & sometimespermanent vertical or horizontaldisplacement of the ground.

Serious consequences for people,

buildings, bridges, freeway overpassesdams, & pipelines.

Focus Place where an earthquake begins.

Epicenter Located on the earths surface directly

above the focus.

Seismic waves. Energy released to relieve earths

internal stress. Move outward from the focus like

ripples in a pool of water.

Shock Waves

Liquefaction of

recent sediments

causes buildings to

sink

Two adjoining

plates move

laterally along the

fault line Earth

movements

cause floodi

low-lying are

Landslides

may occur

on hilly

ground

Shock

waves

EpicenterFocus Effects of a

Earthquake


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How do scientists measure the severityof an earthquake?

A seismograph records the magnitude(measure of ground shaking) of itsseismic waves as indicated by the

amplitude (size) of the shock waves. They use the Richter scale: each unit

has amplitude 10 times greater than thenext smaller unit. A magnitude 5.0 earthquake would result in

10 times more ground motion than amagnitude 4.0 earthquake.

Using the Richter scale, comparethe amount of ground movementfrom a magnitude 7.0 quake to

that of a 5.0 quake.

7.0 6.0 5.0

10 x 10

A magnitude 7.0 earthquake is 100times greater than that of a magnitud5.0 earthquake.

Seismologists Rate Earthquakes: Insignificant = less than 4.0

Minor = 4.0 to 4.9

Damaging = 5.0 to 5.9

Destructive = 6.0 to 6.9

Major = 7.0 to 7.9

Great = over 8.0

Largest recorded land earthquake inChile on May 22, 1960 & measured 9.5on the Richter scale.

Areas of greatest earthquake (seismic) risin the United States.

Earthquakes often release aftershocks that

gradually decrease in frequency over timeup toseveral months.

Some are preceded by foreshocks.

Areas of greatest earthquake(seismic) risk in the world.

To reduce loss of life & property

Examine historical records & geologicmeasurements to locate active faultzones.

Map high-risk areas & establish buildincodes to regulate placement & design obuildings in such areas. Engineers can design homes, buildings, bridges

freeways to be more earthquake resistant more expensive.

People can evaluate the risk & decidewhere to live.


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Tsunami

Series of large waves generated whenpart of the ocean floor suddenly risesor drops.

Caused when faults in the ocean floormove up or down as a result of a largeunderwater earthquake, or sometimesby a volcanic eruption.

Sometimes called tidal wavesbut theyhave nothing to do with the tides.

Tsunamis can

Travel far across the ocean at speedsas high as jet planes.

Hit a coast as a series of towering waof water that can level buildings.

Be detected through a network ofocean buoys to provide some degree oearly warning.

Tsunamis can

Also be detected through use of apressure recorder on the oceanfloor.

Measures changes in water pressureas tsunami waves pass over it.

These data are relayed to a weather

buoy, which then transmits the datavia satellite to tsunami emergencywarning centers.

December 2004: Largest loss of life from a tsunami whengreatunderwater earthquake (9.5 onRichter scale) occurred in the IndianOcean. Generated waves as high as 100 feet (31

meters). Killed 228,000 people. Devastated coastal areas of Indonesia,

Thailand, Sri Lanka, South India, & eastern

Africa. No buoys or pressure gauges were in place

the Indian Ocean to provide early warning.

Earthquake in sea floorswiftly pushes waterupwards, and starts aseries of waves.

Waves move rapidlyin deep oceanreaching speeds ofup to 890kilometers per hour.

As the waves near landthey slow to about 45kilometers per hour butare squeezed upwards andincreased in height.

Waves headinland causingdamage in theirpath.

Undersea thrust fault

Upward waveBangladesh

India

Thailand

Sri Lanka Malaysia

EarthquakeSumatra

Indonesia

December 26, 2004, tsunami

Burma

Formation of atsunami and mapof area affected

by a largetsunami in

December 2004.

Role of Marine Ecosystems: Satellite observations & ground studies point

to the role that coral reefs & mangrove foresplayed in reducing the death toll & destructio

from the 2004 tsunami. Intact mangrove forests in parts of Thailand helpto protect buildings & people from the force of huwaves.

However, extensive damage & high deaths in IndiaTamus state attributed to the clearing of a third its coastal mangrove forests in recent decades.

In Sri Lanka, some of the greatest damage occurrwhere illegal coral mining & reef damage had caussevere beach erosion.


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The Earths crust consistsmostly of minerals and rocks

Mineral: an element or inorganiccompound that occurs naturally in the

earths crust as a solid with a regularinternal crystalline structure. Au (gold), Ag (silver), C (diamonds), NaCl

(salt), SiO2 (quartzite)

Rock: a solid combination of one or moreminerals found in the earths crust. Limestone, granite, feldspar, quartz, mica

Rock is placed in 3 classesbased on the way it forms:

Sedimentary Igneous

Metamorphic

Sedimentary Rock Forms from sediments of dead plant &

animal remains & existing rocks thatare weathered & eroded into tinyparticles that are transported bywater, wind, or gravity to downstream,downwind, downhill, or underwatersites.

Sediments are deposited in layers thataccumulate over time & increase theweight & pressure on underlying layers.

sandstone& shale(formed from pressurcreated by deposited layers of mostlysand)

dolomite& limestone(formed form thecompacted shells, skeletons, & otherremains of dead organisms)

lignite(brown coal) & bituminous(softcoal) (derived from compacted plant

remains). Gemstones include jasper, malachite, opa

and zircon.

Examples of Sedimentary Rock:

Forms below or on the earthssurface when magma wells up fromthe earths upper mantle or deepcrust & then cools and hardens.

Forms the bulk of the earths crust;often covered by sedimentary rocks& soil.

Igneous Rock Intrusive Igneous Rocks formed fro

the solidification of magma belowground. granite

Extrusive Igneous Rocks formed frothe solidification of lava above ground lava rock, pumice, basalt, obsidian

Gemstones formed are diamond,tourmaline, garnet, emerald, amethysttopaz.

Examples of Igneous Rock:


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Metamorphic Rock When preexisting rock is subjected to

high temperatures (which may cause itto partially melt), high pressures,chemically active fluids, or a

combination of these agents. These forces transform a rock by

reshaping its internal crystallinestructure along with its physicalproperties & appearance.

Location deep within the earth.

Examples of Metamorphic Rock

anthracite(a form of coal = hard coal)

slate(formed when shale & mudstone

are heated) marble(produced when limestone is

exposed to heat and pressure)

Gemstones include the turquoise, rubysapphire, zircon.

Rock Cycle Interaction of physical & chemical

processes that change rocks from onetype to another.

Largest & the slowest of the earthsBGC cycles. Takes millions of years.

Rocks are broken down, eroded, crushed,

heated, melted, fused together by heat &pressure, cooled, &/or recrystallizedwithin the mantle & in the crust.

Erosion

Transportation

Weathering

Deposition

Igneou

Rock

granite

pumicbasalt

Sedimentary

Rocksandstone,

limestone Heat, pressure

Cooling

Heat, pressure,stress

Magma(molten rock)

Melting

Metamorphic Rock

slate, marble,

gneiss, quartzite

Rock Cyc

This cycleconcentrates t

planetsnonrenewable

mineral resourcewhich we depen

Oxygen The most abundant elementin

Earths crust.

Nitrogen The most abundant elementinthe Earths atmosphere.

Iron

The most abundant metalinthe Earths core.


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Aluminum Most abundant metalin theEarth's crust, (and the third

most abundant elementtherein, after oxygen andsilicon).

The element commerciallyextracted from bauxite ore.

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Geologic Processes

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