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Natural Hazards, 1e

Introduction to Natural Hazards

Chapter 1

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Learning ObjectivesKnow the difference between a disaster and a catastrophe

Know the components and processes of the geologic cycle

Understand the scientific method

Understand the basics of risk assessment

Recognize that natural hazards that cause disasters are generally high-energy events caused by natural Earth processes

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Learning Objectives, cont.

Understand the concept that the magnitude of a hazardous event is inversely related to its frequency

Understand how natural hazards may be linked to one another and to the physical environment

Recognize that increasing human population and poor land-use changes compound the effects of natural hazards and can turn disasters into catastrophes

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Processes & Natural Hazards

Internal forces within EarthPlate tectonics

Result of internal energy of the earth

External forces on Earth’s surfaceAtmospheric effects

Energy from the sun

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Some Important Definitions

HazardNaturally occurringEffects on human interests

DisasterEffect of hazard on society

Property damage, injury, loss of life

CatastropheMassive disaster

6Figure 1.4

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Natural Hazards & Catastrophes

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History & Natural Hazards

Natural hazards are repetitive.

History of an area gives clues to potential hazards.Maps, historical accounts, climate, and weather data

Rock types, faults, folds, soil composition

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Plate Tectonics

Explains the dynamic processes of the earth’s surface

Due to internal energy of the earth

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Earth’s Internal Structure

Inner core is extremely hot and solid.

Asthenosphere (upper mantle) is composed of solid, hot magma with some flow.

Lithosphere is a thin and brittle crust.

Figure 1.7b

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Plate Tectonics, cont.

Lithosphere is broken into plates that slip on the asthenosphere.

Convection currents caused by hot inner core push and pull on plates.

Two types of lithosphereOceanic - dark, denseContinental - light, buoyant

12Figure 1.9

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Convection and Tectonics

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Plate Boundaries

Dynamic events on the earth’s surface occur when plates move.

Diverge, converge, or slide past each other

Plates are not defined by oceans or continents, but by where the breaks occur.

Where the earthquakes are located

15Figure 1.8

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Plate Boundary Features

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Divergent Plate Boundaries

Where plates move away from each other

New lithosphere is created here

Divergence between two ocean plates:Causes mid-ocean ridges

Seafloor spreading

Ex: Mid-Atlantic Ridge

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Forming a Divergent Boundary

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Seafloor Spreading and Plate Boundaries

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Seafloor Spreading and Seafloor Magnetization

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Convergent Plate Boundaries

Where plates collide

Collisions with oceanic lithosphere results in: Subduction Zones

More dense ocean plates sink and melt.Melted magma rises to form volcanoes.

Collisions between two continental plates results in: Continental Collision Boundary

Neither plate subducts, instead the plates crunch together.Form large mountains such as Himalayas.

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Tectonic Settings and Volcanic Activity

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Transform Boundary

Plates slide past one another

Mostly occur in the ocean

Ex.: San Andreas Fault

Separates the Pacific from the North American plate

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Motion at Transform Boundaries

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Motion at Plate Boundaries

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Hot Spots

Not related to plate boundaries

Spot on Earth where magma rises up from deep in the mantle

Magma causes volcanoes to form.

Ex.: Yellowstone Park and Hawaiian Islands

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Hot Spot Volcano Tracks

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Rock Cycle

Different rocks are formed by different processes.

Rock types in a location give clues to geological past and present.

29Figure 1.12

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Hydrologic Cycle

Solar energy drives movement of water between atmosphere and oceans and continents.

Figure 1.13

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Hydrologic Cycle

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Biogeochemical Cycle

Combines the three previous cycles.

Transfer of chemical elements through a series of reservoirs.

Many important chemical elements are not well understood.

Carbon, Nitrogen, Phosphorus

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Fundamental Concepts for Understanding Natural Processes as Hazards

1. Hazards are predictable from scientific evaluation.

2. Risk analysis is an important component in our

understanding of the effects of hazardous processes.

3. Linkages exist between different natural hazards as well

as between hazards and the physical environment.

4. Hazardous events that previously produced disasters

are now producing catastrophes.

5. Consequences of hazards can be minimized.

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1. Hazards are Predictable

Basis of science is explanation.

Geologists observe hazardous events and form a possible explanation.

From this explanation, a hypothesis is formed.

Data is taken to test a hypothesis.

This is the basis of the scientific method.

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Hazards are Natural Processes

They are a result of natural forces.

They become hazardous when they interfere with human activity.

These process are NOT within our control.Or maybe should not be

Best solution is preparation.

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Ta

ble

1.3

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Forecast & Prediction

PredictionSpecific date, time, and magnitude of event

ForecastRange of probability for event

Some hazards can be predicted, most can be forecasted.

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Hazard Reduction

Identify the location of probable event

Determine probability of event

Observe precursor events

Forecast or predict event

Warning the public

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Figure 1.14

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2. Risk Assessment

Risk = (probability of event) x (consequences)

Consequences: damages to people, property, economics, etc.

Acceptable risk is the amount of risk that an individual or society is willing to take.

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3. Links

Hazards are linked to each other.Some events may cause others.

Example: Earthquakes and landslides

Hurricanes, Tsunami’s & Flooding

Physical environment is linked to hazards.Example: Some rock types are prone to subsidence.

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4. Disasters are Now Becoming Catastrophes

Concentration of population creates greater loss of life in disaster.

Human population growth puts greater demand on Earth’s resources.

Land use affects magnitude and frequency of events.

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5. Consequences Can Be Minimized

Move from reactive response: Recovery and restoration

To an anticipatory response: Avoiding and adjusting to hazards

Land-use planningBuilding codesInsuranceEvacuationDisaster preparednessArtificial control

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Benefits of Hazards

There are some benefits to hazards.

Examples:Flooding provides nutrients for soil.

Landslides form dams to create lakes.

Volcanoes create new land.

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End

Introduction to Natural Hazards

Chapter 1