Earth’s Topographic RegionsCrustal Formation ProcessesCrustal Deformation ProcessesOrogenesis (Mountain Building)EarthquakesVolcanism

GEO 101: PHYSICAL GEOGRAPHYGEO 101: PHYSICAL GEOGRAPHYChapter 12: Chapter 12: Tectonics, Earthquakes, Tectonics, Earthquakes,

and Volcanismand Volcanism

EarthEarth’’s Topographic Regionss Topographic Regions

Figure 12.3

EarthEarth’’s Hypsometrys Hypsometry

Figure 12.2

Crustal Formation ProcessesCrustal Formation Processes

All continents have a nucleus of ancient crystalline rock on which the continents “grows” with the addition of crustal fragments and sediments

Such nucleus is called Cratons

Cratons are commonly stable, and are formed more than 2 billion years ago

Crustal Formation ProcessesCrustal Formation Processes

Continental Shields: are regions where cratonsare exposed at the surface

Continental Crust and Terranes: are added to the Cratons through tectonic cycles

TerraneTerrane FormationFormation

Crustal Deformation Crustal Deformation ProcessesProcesses

When the lithospheric plates or crustal blocks move relative to each other, they form different types of structures such as:

• Folding and Broad Warping (bending of the crusts)

• Faulting (Breaking, causes offset)

Crustal Deformation Crustal Deformation ProcessesProcesses

Stress: forces/ unit area (caused by tectonic forces, gravities, and the weight of the overlying rocks)

(Three type of stress: tension, compression, and shear)

Strain: The response of rocks to stress(faulting and folding)

Stress and StrainStress and Strain

Figure 12.7

Figure 12.8

FoldingFolding

Normal FaultNormal Fault

Figure 12.11

Three types of faults

• Normal fault (tension): Hanging wall move downwards relative to footwall• Reverse fault (compression): Hanging wall move upwards relative to

footwall• Strike-slip fault (lateral shearing): Blocks move along the fault plane

horizontally

Reverse FaultReverse Fault

Figure 12.11

StrikeStrike--slip Faultslip Fault

Figure 12.11

Figure 12.12

San Andreas San Andreas FaultFault

Faulted LandscapesFaulted Landscapes

Figure 12.14

Orogenesis (Mountain Building)Orogenesis (Mountain Building)

Three Types of Three Types of OrogeniesOrogenies::OceanicOceanic--continental plate collisioncontinental plate collision

Andes, Rocky mountainsAndes, Rocky mountains

OceanicOceanic--continental continental CollisionCollision

Figure 12.16

Orogenesis (Mountain Building)Orogenesis (Mountain Building)

Three Types of Three Types of OrogeniesOrogenies::OceanicOceanic--oceanic plate collisionoceanic plate collision

Western pacific such as Japan and Indonesia, the Western pacific such as Japan and Indonesia, the PhilippinesPhilippines

OceanicOceanic--oceanic oceanic CollisionCollision

Figure 12.16

Orogenesis (Mountain Building)Orogenesis (Mountain Building)

Three Types of Three Types of OrogeniesOrogenies::ContinentalContinental-- continental collisioncontinental collision

HimalayasHimalayasThe Appalachian MountainsThe Appalachian Mountains

ContinentalContinental--continental continental CollisionCollision

Figure 12.16

Convergent Margins: IndiaConvergent Margins: India--Asia CollisionAsia Collision

Orogenesis (Mountain Building)Orogenesis (Mountain Building)

The other type of mountain building:The other type of mountain building:uplifting of Faultuplifting of Fault--blocks by magmas or by blocks by magmas or by isostaticisostaticrebound: rebound: Grand Tetons and the Sierra NevadaGrand Tetons and the Sierra Nevada

Teton Range in WyomingTeton Range in Wyoming

Figure 12.17

EarthquakesEarthquakesExpected Quakes and Those of Deadly Expected Quakes and Those of Deadly Surprise:Surprise:

Earthquakes are mostly along faults and Earthquakes are mostly along faults and plate boundaries plate boundaries

Focus, Epicenter, Foreshock, and Focus, Epicenter, Foreshock, and AftershockAftershock

Focus:Focus: The place where the motion of The place where the motion of seismic waves is initiated (the point where seismic waves is initiated (the point where the slip occurs) the slip occurs) normally in subsurfacenormally in subsurface

Anatomy of an EarthquakeAnatomy of an Earthquake

Figure 12.20

EarthquakesEarthquakes

Epicenter:Epicenter: The area at the surface directly The area at the surface directly above the focusabove the focus

Smaller shocks:Smaller shocks: before the main earthquake before the main earthquake Earthquake Forecast?Earthquake Forecast?

Aftershock:Aftershock: Smaller shocks after the main Smaller shocks after the main earthquakeearthquake

Important for the rescuing arrangementImportant for the rescuing arrangement

Buildup and Release of StressBuildup and Release of Stress

Figure 12.21

Earthquake is recorded by an instrument called:seismograph, andMeasurement is charted on: Richter scaleEarthquake magnitude:

>87-7.96-6.9

SeismographsSeismographs

VolcanismVolcanismLocation and Types of Volcanic ActivityLocation and Types of Volcanic ActivityEffusive Eruptions: Gentle eruptions. Magma contains less gases Effusive Eruptions: Gentle eruptions. Magma contains less gases and is rich in iron and is rich in iron and magnesium, thus has low viscosity. Exampleand magnesium, thus has low viscosity. Example---- HawaiHawai’’iiExplosive Eruptions: Violent eruptions. Magma contain more gasesExplosive Eruptions: Violent eruptions. Magma contain more gases and silica and and silica and has a high viscosity has a high viscosity block the conduitsblock the conduits causing high pressure buildup. causing high pressure buildup. Examples: along Examples: along subductionsubduction zones. zones.

Figure 12.25

Explosive eruptionsEffusive eruptions

EarthEarth’’s Topographic Regionss Topographic RegionsPlains Plains

High tablelands (Colorado plateau)High tablelands (Colorado plateau)Hill and low tablelandsHill and low tablelandsMountainsMountainsWidely spaced mountainsWidely spaced mountainsDepressionsDepressions

See figure 12.3See figure 12.3

Chapter 12: Chapter 12: ReviewReviewTectonics, Earthquakes,and VolcanismTectonics, Earthquakes,and Volcanism

Crustal Formation ProcessesCrustal Formation ProcessesAll continents have a nucleus (All continents have a nucleus (CratonsCratons ) of ancient ) of ancient crystalline rock crystalline rock Continental Crust and Continental Crust and TerranesTerranes are added to the are added to the CratonsCratons through tectonic cyclesthrough tectonic cyclesContinental Shields:Continental Shields: are regions where are regions where cratonscratons are are exposed at the surfaceexposed at the surface

Chapter 12: Chapter 12: ReviewReviewTectonics, Earthquakes,and VolcanismTectonics, Earthquakes,and Volcanism

Crustal Deformation ProcessesCrustal Deformation ProcessesCrustal blocks are stressed by tectonic forces, Crustal blocks are stressed by tectonic forces, gravity, and overlying rocksgravity, and overlying rocksStress ( Tension, Compression, Shear)Stress ( Tension, Compression, Shear)Bending (folding) Bending (folding) Breaking of the curst (Faults)Breaking of the curst (Faults)

Chapter 12: Chapter 12: ReviewReviewTectonics, Earthquakes,and VolcanismTectonics, Earthquakes,and Volcanism

ResultsResultsBending (Folding) Bending (Folding) Breaking of the curst (Faults)Breaking of the curst (Faults)

Chapter 12: Chapter 12: ReviewReviewTectonics, Earthquakes,and VolcanismTectonics, Earthquakes,and Volcanism

Figure 12.11

Three types of faults

• Normal fault (tension): Hanging wall move downwards relative to footwall

Reverse FaultReverse Fault

Figure 12.11

• Reverse fault (compression): Hanging wall move upwards relative to footwall

StrikeStrike--slip Faultslip Fault

Figure 12.11

• Strike-slip fault (lateral shearing): Blocks move along the fault plane horizontally

Anatomy of an EarthquakeAnatomy of an Earthquake

Figure 12.20

VolcanismVolcanism

Figure 12.25