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Find an event that occurred this week that moves you. You must be able to relate it to the current chapter in some way – creativity is welcome. For instance, let’s say you read about the war in Afghanistan and parts of Pakistan. After reading the article, you check a world map and find that some remote parts of Pakistan are near the Himalayan Mountain Range. You will discover in Chapter 3 that the Himalayas were formed by a convergence of two continental plates, the Indian plate and the Eurasian plate, which causes a convergence zone that resulted in mountain uplift. And, voila!, the Himalayans are formed.

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Remember, geology is all about connections. The physical environment always sets the context for human events, and, often, they have a more direct influence than you may initially imagine. For example, you’re not worried about a tsunami if you live in North Dakota, but you are much more aware of the Pleistocene glaciations than you would be if you lived in Arizona.

You may use an article from the following sources:

Reuters

National Public Radio

Another news outlet if you include a paragraph telling me why you chose it.

Turn in:

A document that includes the entire story (copy and pasted from the original site).

The citation (where you got it and when).

The link.

A map of the location of the event that was not included in the article.

Paragraph of what you think about the news (good, bad, indifferent – just tell me why).

Paragraph explaining at least one geologic connection that relates to this week’s chapter.

© 2012 Pearson Education, Inc.

Case History: Hurricane Katrina (1)

• Made Landfall in August 29, 2005 to the east of New Orleans

• Storm Surge: 3 to 6 m (9 to 20 ft)

• Diameter of serious damage path: About 160 km (100 mi)

• 80 percent of New Orleans under water

• Official number of deaths: 1,836

• Property damages: Tens of billions

• Estimated costs for recovering and rebuilding: hundreds of billions

© 2012 Pearson Education, Inc.

Case History: Hurricane Katrina (2)

• Regional subsidence: 1 to 4 m (3 to 12 ft) per 100 yrs

• Sea level rise: 20 cm (8 in.) last 100 yrs due to global warming and extraction of GW, oil and gas

• Geographic location: Vulnerable to hurricanes, storms, and inland floods

• Aware of risks and warnings in place

• Insufficient funds for monitoring and maintaining the levee and floodwalls

• Poor coordination in initial emergency response efforts

• Rebuild: Better design and planning, better technology and knowledge, broader awareness

© 2012 Pearson Education, Inc.

Hurricane Katrina

Figure 5.1

© 2012 Pearson Education, Inc.

Natural Disaster, Hazards (1)

• Criteria: A particular event in which 10 or more people are killed; one hundred or more people are affected; a declaration of emergency is issued, or there is a request for international assistance

• Dangerous natural processes, including earthquakes, floods, volcanic activities, landslides, and storms

© 2012 Pearson Education, Inc.

Natural Disaster, Hazards (2)

• The occurrences of natural disasters on a world scale are increasing

• Natural disaster causing great loss of life and/or property damage

• Earthquakes, floods, cyclones (hurricanes) killed several million people, with an average worldwide annual loss of life of about 150,000 people

• Annual average property damage exceeds $50 billion

• Impact risks, depending on the nature of hazards, spatial and temporal relations to human environment

© 2012 Pearson Education, Inc. From NOAA 99044-CD

Types of Natural Hazards

© 2012 Pearson Education, Inc.

Why Natural Processes Become Hazards

• Natural processes become hazardous: When people live or work in areas where they occur

• Land-use changes, such as urbanization or deforestation

• Better environmental planning:Simply not to build on floodplains, earthquake prone areas

• Consumption of energy resources and climate changes

© 2012 Pearson Education, Inc.

Hazard Magnitude and Frequency

• Magnitude: Intensity of a natural hazard in terms of the amount of energy released

• Frequency: Recurrence interval of a disastrous event

• Magnitude and Frequency: Generally an inverse relation between them

• More damages associated with hazards of moderate frequency and magnitudes

© 2012 Pearson Education, Inc.

Magnitude, Frequency, and Impact Risk

• Magnitude and Frequency: Largely controlled by natural factors

• Impact risk: Controlled by both natural and human factors

• Low-magnitude and high-frequency hazards not always destructive, a high magnitude one almost certainly catastrophic

• Commonly, most impact risks from natural processes of moderate magnitude and moderate frequency

© 2012 Pearson Education, Inc.

Mixed Blessings of Natural Hazards

• Not all hazardous processes exert harmful or deadly consequences

• Benefits: Creating new land, supplying nutrients to soil, flushing away pollutants, changing local landscape

• Fault gouge has formed groundwater barriers, producing natural subsurface dams and water resources

© 2012 Pearson Education, Inc.

Damages of Natural Hazards (1)

• Death and damages: Great loss of human life, grave damages to property, changes in properties of Earth materials

• More life loss from a major natural disaster in a developing country; more property damage in a more developed country

• Catastrophe: Disastrous situations requiring a long process to recovery from grave damages

© 2012 Pearson Education, Inc. Table 5.1

Catastrophic Potential of Hazards

© 2012 Pearson Education, Inc.

Hazard Evaluation (1)

Fundamental Principles

• Most natural hazards: Identified and studied using the scientific method and predictable from scientific evaluation

• Risk analysis: A critical component in understanding impacts

• Different hazards are linked

• Hazardous events repetitive

• Importance of hazard planning and hazard mitigation

© 2012 Pearson Education, Inc.

Hazard Evaluation (2)

• Study historic data: Hazards are repetitive events

– Occurrence and recurrence intervals

– Location and effects of past hazards

– Observations of present conditions

– Measuring the changes or rates of change

– Historic trends of hazards

© 2012 Pearson Education, Inc.

Hazard Evaluation (3)

• Studying linkages: Spatial and temporal links

– Linkages between adjacent locations

– Linkages between past, present, and future conditions

– Linkages between hazards (e.g., volcano and mudflow)

– Geologic setting and hazards (e.g., rock fractures and landslides)

© 2012 Pearson Education, Inc.

Disaster Forecast, Prediction, and

Warning (1)

• Forecast: The certainty of the event is given as the percent chance of happening

• Prediction: Sometimes possible to accurately predict when, where, type and size of the certain natural hazardous events

• Warning: A hazardous event has been predicted or a forecast has been made, the public must be warned

© 2012 Pearson Education, Inc.

Disaster Forecast, Prediction, and

Warning (2)

• Locations, precursors, probability of occurring

• Determining the probabilities of a hazardous event at a given magnitude

• Observing precursor events or signs

• Forecasting the hazard

• Warning the public

© 2012 Pearson Education, Inc.

Disaster Prediction and Warning (2)

Figure 5.14

© 2012 Pearson Education, Inc.

Scientists, Hazards, and the Media

• The media are generally more interested in the impact of a particular event on people than in its scientific aspects

• Good relations between scientists and the news media is a goal that may be difficult to always achieve

• Scientists have an obligation to provide the public with information about natural hazards

• Reports concerning people’s lives and property should be conservative evaluations based on the evidence at hand

• Provide their readers, viewers, or listeners with accurate information that have been verified

© 2012 Pearson Education, Inc.

Risk Assessment

• Risk determination

– Type, location, probability, consequences

– Risk estimate: Product of probability and consequences

• Risk Threshold: Acceptable risks

– Put probability and consequences into perspective

– Society’s perception and willingness

• Limitations and opportunities of risk assessment

© 2012 Pearson Education, Inc.

Risk Impact (1)

Hazardous Earth processes and risk impact statistics for the past two decades

• Annual loss of life: About 150,000

• Financial loss: > $50 billions

• More life loss from a major natural disaster in a developing country (2003 Iran quake, ~30,000 people)

• More property damage occurs in a more developed country

© 2012 Pearson Education, Inc.

Risk Impact (2)

Risk impact estimation:

• To human life: Potential loss and injury of life

• To property: Damage and destruction

• To society: Services and functions of society

• To economy: Manufacture, mining, commercial, real estate, etc.

• To natural environment: Direct or indirect adverse impact

© 2012 Pearson Education, Inc.

Human Response to Hazards (1)

Reactive response

• Primarily after the hazardous event

• Recovery phases: Search response, rescue, restoration, and reconstruction

• Recovery period: Recovery length depending on the magnitude of hazard and impact intensity

© 2012 Pearson Education, Inc.

Human Response to Hazards (2)

Reactive response and recovery priority

• Critical needs: Emergency operations, critical infrastructure, hospitals, shelter, food, and water supply

• Essential function: Transportation, communication, education, and other services

• Improvement and development: Rebuild damaged structures and develop better structures

© 2012 Pearson Education, Inc.

Human Response to Hazards (3)

Anticipatory Response: Perceiving, Avoiding, and Adjusting to Hazards for avoiding or minimizing the impacts of disasters

• Land-use planning

• Insurance and other regulations for safety measures

• Evacuation

• Disaster awareness and preparedness: Individuals, families, cities, states, or even entire nations can practice

© 2012 Pearson Education, Inc.

Human Response to Hazards (4)

General response in a given location

• Combination of reactive and anticipatory response

• Artificial control of natural processes

• Taking no or little action, being optimistic about chances of making it through disasters

© 2012 Pearson Education, Inc. Figure 5.19

Global Climate and Hazards

© 2012 Pearson Education, Inc.

Population Growth and Natural Hazards

• Increase in population puts a greater number of people at risk

• Asia suffered the greatest losses from 1985 to 1997, with 77 percent of the total deaths and 45 percent of the economic losses

• Deadly catastrophes resulting from natural hazards linked to changes in land use, Hurricane Mitch in 1998, flooding of the Yangtze River in 1998, and Hurricane Katrina in 2005

• In quest: Artificially controlling some natural hazards

© 2012 Pearson Education, Inc.

Land-Use Change and Natural Hazards (1)

• Land-use change amplifying the impact risks of natural hazards

• Deforestation and fire in Honduras before Hurricane Mitch, 11,000+ deaths – Massive deforestation in major river basin (e.g.,

85 percent forest loss in Yangtze River, 4000+ deaths)

– Inappropriate construction code in tectonic earthquake zone, 2003 Iran earthquake, ~300,000 deaths

– Poor construction in Haiti, 2010 earthquake, above 300,000 death

© 2012 Pearson Education, Inc. Figure 5.20

Land-Use Change and Increase in

Natural Hazards (2)

© 2012 Pearson Education, Inc.

Applied and Critical-Thinking Topics

• List all the natural hazardous processes in the are where you live. What is done? What is more to be done?

• Construct a U.S. vulnerability map of natural hazards by state, or construct a state map by county.

• What is the difference between forecasting and warning

• Can humans eventually control the impact risks of natural hazards? Explain your rationale.

© 2012 Pearson Education, Inc.

End of Chapter 1

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Cosmology  Conscious thought distinguishes humans.

 Developed across 1,000s of generations.

 Lends us curiosity, insight, and the ability to learn.

 As a result, we seek to explain our surroundings.

 Where do we come from?

 Where do we fit in the Universe?

 Why are we here?

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Cosmology  Study of the structure and history of the Universe.

 Cosmology is a complicated science.

 Requires thinking in unfamiliar scales of space and time.

Spatial scales.

Attometers (10-21 meters), to

10s of billions of light years (9.4622 meters +).

Temporal scales.

Attoseconds (10-21 seconds), to

10s of billions of years (3.1517 seconds +).

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Earth’s Changing Place  3,000 years ago, humans knew the heavens well.

 They knew that stars were fixed relative to other stars.

 They knew that stars moved predictably across the sky.

 They saw retrograde motion separating planets from stars.

 They did not think of Earth as a planet, however.

 Movement in the heavens was attributed to deities.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

An Evolving Image of Earth  The ancients thought the Universe was geocentric.

 Heavenly bodies circle around a motionless central Earth.

 “Proven” by Ptolemy (100–170 B.C.), the idea was wrong.

 The idea held as religious dogma for 1,400 years.

 A heliocentric (sun-centered)

universe was proposed by

the Greeks ~ 250 B.C.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Renaissance  Rebirth of rational thought in 15th century Europe.

 Spawned a new age of scientific discovery.

 Copernicus – Published evidence for heliocentricity.

 Kepler – His elliptical planetary orbits refuted Ptolemy.

 Galileo – Observed moons orbiting Jupiter.

 Newton – Planet motion explained by his Theory of Gravity.

 Natural laws governed

natural events.

 Geocentricity faded away.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Solar System

 Solar system: A sun, planets, moons and other objects.

 Earth shares the solar system with 7 planets. A planet…

 Is a large solid body orbiting a star (the Sun).

 Has a nearly spherical shape.

 Has cleared it’s neighborhood of other objects.

 Moon – A solid body locked in orbit around a planet.

 The solar system also includes asteroids and comets.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The PlanetsThe Planets  Two groups of planets occur in the solar system.

 Terrestrial (Earthlike) – Small, dense, rocky planets.

Mercury, Venus, Earth, and Mars.

 Jovian (Jupiter-like) – Large, low density, gas-giant

planets.

Jupiter, Saturn, Uranus, and Neptune.

 Pluto is no longer considered to be a planet.

 Two groups of planets occur in the solar system.

 Terrestrial (Earthlike) – Small, dense, rocky planets.

Mercury, Venus, Earth, and Mars.

 Jovian (Jupiter-like) – Large, low density, gas-giant

planets.

Jupiter, Saturn, Uranus, and Neptune.

 Pluto is no longer considered to be a planet.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Solar SystemThe Solar System  The Terrestrial planets are the 4 most interior.

 The Jovian planets occupy the 4 outermost orbits.

 The asteroid belt lies between Mars and Jupiter.

 Planet orbital planes lie within 3o of the Sun’s equator.

 The Terrestrial planets are the 4 most interior.

 The Jovian planets occupy the 4 outermost orbits.

 The asteroid belt lies between Mars and Jupiter.

 Planet orbital planes lie within 3o of the Sun’s equator.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Solar System FormationSolar System Formation  The Nebular Theory.

 A 3rd, 4th or nth generation nebula forms ~4.56 Ga.

 Hydrogen and Helium left over from the big bang.

 Heavier elements produced by stellar nucleosynthesis.

 This material coalesces into an accretion disc.

 The Nebular Theory.

 A 3rd, 4th or nth generation nebula forms ~4.56 Ga.

 Hydrogen and Helium left over from the big bang.

 Heavier elements produced by stellar nucleosynthesis.

 This material coalesces into an accretion disc.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Solar System FormationSolar System Formation  The ball at the center grows dense and hot.

 Fusion reactions begin; the Sun is born.

 Dust in the rings condenses into particles.

 Particles coalesce to form planetesimals.

 The ball at the center grows dense and hot.

 Fusion reactions begin; the Sun is born.

 Dust in the rings condenses into particles.

 Particles coalesce to form planetesimals.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Solar System FormationSolar System Formation  Planetesimals accumulate into a larger mass.

 An irregularly-shaped proto-Earth develops.

• The interior heats up and becomes soft.

• Gravity shapes the Earth into a sphere.

• The interior differentiates into a-Fe core and stony mantle.

 Planetesimals accumulate into a larger mass.

 An irregularly-shaped proto-Earth develops.

• The interior heats up and becomes soft.

• Gravity shapes the Earth into a sphere.

• The interior differentiates into a-Fe core and stony mantle.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Solar System FormationSolar System Formation

 Soon, a small planetoid collides with Earth.

 Debris forms a ring around the Earth.

 The debris coalesces and forms the Moon.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Solar System FormationSolar System Formation  The atmosphere develops from volcanic gases.

 When the Earth becomes cool enough.

 Moisture condenses and accumulates.

 Comet bombardment adds more water.

 The oceans are born.

 The atmosphere develops from volcanic gases.

 When the Earth becomes cool enough.

 Moisture condenses and accumulates.

 Comet bombardment adds more water.

 The oceans are born.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Solar System FormationSolar System Formation

Synopsis

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Earth  What would solar system visitors notice about Earth?

 A magnetic field.

 An atmosphere.

 Surface features.

Continents.

Oceans.

Polar ice caps.

Evidence of humanity?

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Celestial Neighborhood  Interstellar space is a vacuum with scarce matter.

 Matter greatly increases approaching the Sun.

 The Sun ejects matter into space as the Solar Wind.

 Solar Wind…

 Magnetically charged particles.

 Stream outward in all directions.

 Consists of…

Protons (+ charge).

Electrons (– charge).

 A small percentage of the

Solar Wind hits Earth.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Magnetic Field

 Like a bar magnet, Earth has a dipolar magnetic field.

 Magnetic field lines flow from N to S and…

 Extend into space and weaken with distance from Earth.

 Create a shield around Earth (the magnetosphere).

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Van Allen BeltsThe Van Allen Belts  The solar wind is deflected by the magnetosphere.

 Near Earth, the stronger magnetic field forms the Van

Allen belts, which arrest deadly cosmic radiation.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Aurorae  Some ions escape Van Allen belts.

 Pulled to the magnetic poles, the ions generate light.

 Spectacular aurora follow solar flares.

 Aurora borealis – Northern lights.

 Aurora australis – Southern lights.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Atmosphere  Earth, with an atmosphere, is unique among the planets

 Densest at sea-level, the atmosphere thins upward.

 The atmosphere is mostly nitrogen (N2).

 Oxygen was absent from the atmosphere before 2.5 Ga.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Atmosphere

 99% of atmosphere is below 50 km.

 The rest (1%) is between 50 and 500 km.

Sea-level atmospheric P = 14.7 psi.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Atmosphere

 The atmosphere is layered.

 Troposphere (0–11 km).

Mixing layer.

Weather is limited to this layer.

 Tropopause (11–12 km).

 Stratosphere (12–47 km).

 Mesosphere (47– 81 km).

 Thermosphere (> 81 km).

 Boundaries between layers are

termed “pauses.”

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Surface Features  Earth’s surface: continents are high; oceans are low.

 Due to the differing buoyancy of each type of crust.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Elemental Composition  90% percent of Earth is comprised of 4 elements.

 Iron (Fe) – 35%

 Oxygen (O) – 30%

 Silicon (Si) – 15%

 Magnesium (Mg) – 10%

 The remaining elements?

 Form 10% of Earth.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Earth Materials  Organic chemicals – Carbon containing compounds.

 Biological remains (wood, peat, lignite, coal, and oil).

 Geologically rare (decompose in contact with oxygen).

 Minerals – Inorganic crystalline solids.

 Comprise rocks and, hence, most of the earth.

 Most minerals on Earth are silicates (based on Si and O).

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Earth Materials  Glasses – Noncrystalline mineral-like matter.

 Rocks – Aggregates of minerals. There are many types.

 Igneous – Cooled from a liquid (melt)

 Sedimentary – Debris cemented from preexisting rock.

 Metamorphic – Rock altered by pressure and temperature.

 Sediments – Accumulations of loose mineral grains.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Earth Materials  Metals – Solids made of metallic elements.

 Melts – Rocks that have been heated to a liquid.

 Magma – Molten rock beneath the surface.

 Lava – Molten rock at the surface.

 Volatiles – Materials that turn into gas at the surface.

 H2O, CO2, CH4,and SO2,

 Volatiles are released from volcanic eruption.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

A Layered Earth  We live on the thin outer skin of Earth.

 Early perceptions about Earth’s interior were wrong.

 Open caverns filled with magma, water, and air.

 Furnaces and flames.

 We now know that Earth

is comprised of layers.

 The Crust.

 The Mantle.

 The Core.

Outer Core.

Inner Core.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

A Layered Earth  Hard-boiled egg – Like an egg, Earth has 3 main layers.

 Earthquakes – Seismic waves pass through Earth.

 Seismic waves permit analysis of the interior.

Wave velocity changes with density.

Velocity changes give depth of layer changes.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Earth’s Interior Layers

© W . W . Norton

 Crust

 Continental

 Oceanic

 Mantle

 Upper

 Lower

 Core

 Outer – Liquid

 Inner – Solid

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Crust  The outermost “skin” of Earth with variable thickness.

 Thickest under mountain ranges (70 km – 40 miles).

 Thinnest under mid-ocean ridges (3 km – 2 miles).

 The Mohorovicic discontinuity is the base of the crust.

 The “Moho” separates the crust from the upper mantle.

 Andrija Mohorovičić found this change in P-wave velocity.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Two Types of Crust  Continental crust – Granitic, underlies the continents.

 Average rock density about 2.7 g/cm3.

 Average thickness 35–40 km.

 Oceanic crust – Basaltic, underlies the ocean basins.

 Density about 3.0 g/cm3.

 Avgerage thickness 7–10 km.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Earth’s Mantle  Solid rock layer between the crust and the core.

 2,885 km thick, the mantle is 82% of Earth’s volume.

 Mantle composition is the ultramafic rock peridotite.

 Below ~100–150 km, the rock is hot enough to flow.

 It convects: Hot mantle rises, cold mantle sinks.

 Three subdivisions: Upper, transitional, and lower.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

The Core

 Outer core

Liquid iron-nickel-sulfur

2255 km thick.

Density – 10-12 g/cm3

 Inner core

Solid iron-nickel alloy.

Radius of 1220 km.

Density – 13 g/cm3.

 An iron-rich sphere with a radius of 3,471 km.

 2 components with differing seismic wave behavior.

 Flow in the outer core

generates the magnetic field.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Lithosphere–Asthenosphere  Lithosphere – The outermost 100–150 km of Earth.

 Nonflowing, rigid material that moves as tectonic plates.

 Made of 2 components: Crust and upper mantle.

 Asthenosphere – Upper mantle below lithosphere.

 Shallow under oceans; deep under continents.

 Flows as a soft solid.

Edited by Joao Santos

Essentials of Geology, 3rd edition, by Stephen MarshakEssentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in ContextChapter 1: The Earth in Context

Next Chapter

Chapter 3

Plate Tectonics

Edited by Joao Santos

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