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Chapter 12Earthquakes and Volcanism

I. Earth’s Surface ReliefI. Earth s Surface ReliefII. OrogenesisIII. Earthquakes

A. What is an earthquakeB. Anatomy of an EarthquakeC. Measuring EarthquakesD. Tsunamis

Plate TectonicsEarthquakes and Volcanoes

Figure 11.20

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I. Earth’s Surface Relief FeaturesCrustal Orders of Relief

First

Second

Third

I. Earth’s Surface Relief FeaturesUplifted Crustal Formations

1 Residual mountains and stable continental cratons formed from1. Residual mountains and stable continental cratons, formed from inactive remnants of ancient tectonic activity

2. Tectonic mountains and landforms, produced by active folding, faulting, and crustal movements

3. Volcanic features, formed by the surface accumulation of molten rock from eruptions of subsurface materials.

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I. Earth’s Surface Relief FeaturesCratons and Continental Shields

Craton – Continental nucleus of ancient crystalline rock on which theancient crystalline rock on which the continent grows with the addition of crustal fragments and sediments.A continental shield occurs where a craton is exposed at the surface.

Figure 12.4

I. Earth’s Surface Relief FeaturesBuilding Continental Crust

Figure 12.5

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Seafloor Spreading and Plate Boundaries

I. Earth’s Surface Relief FeaturesNorth American Terranes

Figure 12.6

Terrane: A migrating piece of Earth’s crust, dragged about by processes of mantle convention and plate tectonics.

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I. Earth’s Surface Relief FeaturesCrustal Deformation Processes

Folding: Rock bends as a result of stress.F lti R k f t lt f t th t i tFaulting: Rock fractures as a result of stress that is greater than the internal strength of the rock.

Crustal Deformation ProcessesA. Folding

Figure 12.11

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Crustal Deformation ProcessesA. Folding

Figure 12.8

Crustal Deformation ProcessesB. Faulting

San Andreas Fault

Figure 12.12

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III. Crustal Deformation ProcessesB. Faulting

Figure 12.11

II. OrogenesisA. Definitions

Orogenesis refers to the building of mountains.Orogenesis refers to the building of mountains.

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II. Orogenesis (Mountain Building)A. Types of Orogenies

1 Oceanic plate-1. Oceanic plate-continental plate collision

2. Oceanic plate-oceanic plate collisioncollision

3. Continental-continental plate collision

III. EarthquakesA. Definitions

An earthquake is a sudden vibration or trembling in the Earthvibration or trembling in the Earth The motion caused by the quick release of stored potential energyinto the kinetic energy of motion.

Focus is the subsurface area along a fault plane where the stress is released.Epicenter is the area at the surface of the earth directly above the focus.

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III. EarthquakesA. Definitions

Types of Seismic Waves:yp1. Body Waves: Waves that travel through the

lithosphere.P-waves = primary wavesS-waves = secondary waves

2. Surface Waves: Travel at or near the Earth's f Th d llisurface. These waves produce a rolling or

swaying motion causing the Earth's surface to behave like waves on the ocean.

III. EarthquakesSan Andreas Fault:

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III. EarthquakesB. Anatomy of an Earthquake

Figure 12.21

III. EarthquakesB. Anatomy of an Earthquake

Figure 12.21

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II. EarthquakesB. Anatomy of an Earthquake

Where do earthquakes occur?1. Faults2. Tectonic plate boundary zones3. Mid-ocean ranges

Earthquakes with magnitude greater than 7.0

Figure 12.21

Earthquakes with magnitude less than 5.0

III. EarthquakesC. Measuring Earthquakes

A seismograph is an instrument that measures the energy contained in seismic waves from an earthquake or other type of ground displacement.

The standard unit of measurement for wave energy is the Richter scale or the moment magnitude scale.

Figure 12.22

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III. EarthquakesC. Measuring Earthquakes

Magnitude in Energy ReleasedRichter Scale in Joules Comment

2 6.3 x 107 Smallest earthquake detectable by people.

5 2.0 x 1012Energy released by the Hiroshima atomic bomb.

6.7 7.1 x 1014 Northridge, California earthquake 1994.7 2.0 x 1015 Major earthquake.

7.4 7.9 x 1015Turkey earthquake August 17, 1999. More than 12,000 people killed.Deadliest earthquake this century.

7.6 1.6 x 1016Tangshan, China, 1976. About 250,000 people died.

8.3 1.8 x 1017San Francisco earthquake of 1906. 700 died.

8.6 5.0 x 1017

Most powerful earthquake recorded in the last 100 years. Southern Chile 1960. Claimed 5,700 lives

Tsunami

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III. EarthquakesTsunamis

III. Earthquakes

Figure 12.22

(CSUN parking lot, 1994)

(Fishing boat beached from a tsunami caused by the 1964 earthquake in the Gulf of Alaska.)

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III. Earthquakes

Figure 12.22