Lecture 1: Overview of Hazards

What are some hazards that pose a risk to humans and the environment?

• nuclear meltdowns

• Toxic gas release

• Oil spills

• Ozone depletion

• Acid rain

• Infrastructure failure

• Shipwrecks

• Airplane crashes

What are the 3 main processes natural hazards can arise from?

1. Internal forces within the Earth

2. External forces on Earth’s surface

3. Gravitational attraction

Internal forces within the earth - driven by what? Example?

Driven by the internal energy of the Earth

Example: Plate tectonics

External forces on earth’s surface - driven by what? Example?

driven by the sun’s energy

example: atmospheric effects

Gravitational attraction - driven by what? Example?

driven by the force of gravity

example: downslope movement

Hazard:

A process that poses a potential threat to people or the environment

Risk:

The probability of an event occurring multiplied by the impact on people or the environment

probability x impact

Disaster:

A brief event that causes great property damage or loss of life

- The carrying out of a hazard

Catastrophe:

A massive disaster

Hazards that are more likely to be catastrophic:

• tsunamis

• earthquakes

• volcanoes

• hurricanes

• floods

Hazards that are less likely to be catastrophic:

• landslides

• avalanches

• wildfires

• tornadoes

What is the impact of a hazard?

Both its magnitude (energy released) and frequency

What is the Magnitude-Frequency Concept?

There is an inverse relationship between magnitude and frequency

3 components of the Geologic Cycle

1. Tectonic cycle

2. Rock cycle

3. Hydrologic cycle

What is the tectonic cycle? 

the creation, movement, and destruction of tectonic plates

What are tectonic plates ?

Large blocks of the Earth’s crust that form its outer shell

How many tectonic plates are there?

14

• 7 big plates - 7 continents

• 7 small plates in between continents

where is new land formed?

mid ocean ridges

where is land destroyed?

subduction zones

What energy drives the tectonic cycle?

Earth’s internal energy

Earth’s internal structure

Core (inner, outer)

Mantle

Asthenosphere (upper mantle)

Lithosphere

Inner core:

extremely hot and solid

Asthenosphere (upper mantle)

composed of hot magma with some flow

Lithosphere:

a thin and brittle crust

What is the crust?

Forms the upper part of the lithosphere and is broken into fragments (plates)

2 types of crusts:

1. Oceanic: dense, thin (avg 7km thick)

2. Continental: relatively buoyant, thick (avg 30 km thick)

What causes the movement of plates?

Convection currents within the mantle

Subduction Zone (image)

Do plate boundaries match up with the boundaries of continents or oceans?

No

3 types of plate boundaries

1. Divergent

2. Convergent

3. Transform

Plate boundaries (map)

What are some evidence for Pangaea?

• Current mountain ranges

• fossils

What are Divergent Plate Boundaries?

At these boundaries, plates move away from each other (diverge)

• new land gets created

• results in seafloor spreading

• oceanic ridges form

  • Example: the Mid-Atlantic Ridge

Is the Atlantic Ocean getting wider or narrower?

(hint, its a divergent plate boundary)

Wider

What are Convergent Plate Boundaries?

At these boundaries, plates move toward each other

• cause collisions - result in different things depending on the type of crusts involved

Collisions involving oceanic and continental crust result in what? (and what forms)

Subduction zones

• dense ocean plates sink and melt

• melted magma rises to form mountains and volcanoes

Collisions involving 2 continental plates results in what? (and what forms)

Collision boundaries

• niether plate sinks

• tall mountain tend to form

What is this image of?

Subduction zone

What is this image of?

Collision boundaries

What are Transform Boundaries?

At these boundaries, plates slide horizontally past each other

• the zone along which the movement occurs is called a transform fault

• most of these faults are located beneath oceans, but some occur on continents

• Example: San Andreas Fault

Plate boundaries summary image

What are Hot Spots?

Spots where magma rises from the mantle, where the currents are strong enough to pull magma up

• found away from plate boundaries

• magma erupting at surface results in the formation of volcanoes

• Example: strings on islands (Hawaiian Islands)

What is this image of?

Hot spots

What is a rock?

An aggregate of one or more minerals

What are the 3 different rock types?

1. Igneous

2. Sedimentary

3. Metamorphic

The Rock Cycle

What is the Hydrologic Cycle?

The movement and exchange of water among the land, atmosphere, and oceans by changes in state

• water cycle

• solar energy drives the movement of water

What is the residence time of a water molecule?

Ranges from days (in the atmosphere) to thousands of years (in the ocean)

The Hydrologic Cycle

What are the 5 major course themes?

1. Hazards can be understood through scientific investigation and analysis

2. An understanding of hazardous processes is needed to evaluate risk

3. Hazards are linked to each other and the environment

4. Population growth and socio-economic changes are increasing the risk from hazards

5. The consequences of hazards can be reduced

Theme 1: Hazards can be understood

Scientists observe a hazardous event and form a possible explanation for the cause

• From this explanations, a hypothesis is formed

• Data are then collected to test the hypothesis

• Knowing the cause allows for the identification of where hazards may occur

• Knowledge of past events aids in predicting future events

Are hazards natural processes?

These events are natural forces; they only become hazardous when they disrupt human activity or the environment

• These processes are not within our control. We cannot prevent them; we can only respond to them

• The best solution to mitigate loss is preparation

What is a prediction?

a specific time, date, location, and magnitude of the event

• only some hazards can be preducted

What is a forecast?

a range of probability for the event

• many hazards can be forecasted

What is risk?

Risk = (probability of event) x (consequences)

What are consequences?

damage to people, property, the environment, the economy

• impacts

What is acceptable risk? 

The amount of risk that an individual is willing to take

• The frequency of an event plays a role in determining acceptable risk

What are 2 examples of how hazards are linked? (theme 3)

• Earthquakes may cause tsunamis and landslides

• Hurricanes may cause tornadoes and flooding

Theme 3: Hazards are linked (image)

Theme 4: The increasing risk of hazards

• Concentration of human population creates greater loss of life in a disaster

• Population growth is putting greater demand on Earth’s resources

• Rapid population growth is currently occurring in most developing countries

• Many people live in areas that are prone to hazards

Explain the human footprint and how it is increasing the risk of hazards

The risks associated with hazards change as human development expands

Examples:

• Neighborhoods extend onto hillsides and floodplains

• Urbanization alters drainage and slopes

• Agriculture, forestry, and mining can increase erosion

• In Canada, property damage from hazards is increasing but deaths from hazards are decreasing (because of better planning and warning).

Socio-economic factors of disaster (developed vs developing countries)

• Economic losses from disasters are much higher in developed countries

• Deaths from disasters are much higher in developing countries

Direct effects vs Indirect effects

Direct effects: deaths, injuries, displacement of people, damage to property

Indirect effects: crop failure, starvation, emotional distress, loss of employment

Reactive approaches to hazards:

• recovery

• search and rescue

• providing food

• water

• shelter

• rebuilding

Proactive approaches to hazards

Adjustment through:

• lang-use planning

• building codes

• insurance

• evacuation planning

• disaster preparedness

• artificial control

What are benefits of hazardous events called?

Natural service functions

Examples of natural service functions:

• Flooding provides nutrients for the soil

• Landslides form natural dams that create lakes

• Volcanic eruptions create new land

Climate change & natual hazards

Global climate change is currently the most crucial environmental issue facing the Earth

• As climate changes, the frequency of some natural processes will increase.

• The sea level rise from melting ice sheets will cause more coastal erosion and flooding

• Warmer oceans will cause for frequent hurricanes

Which mountain chain is the result of an ocean-continent subduction zone?

The Andes