Comprehensive Hazards and Climate Change: Earthquakes, Volcanoes, Tsunamis, and Mitigation

Earthquakes

Result from the rupture of rocks along a fault, energy released in form of seismic waves; epicenter is on surface, focus is directly below it

Richter Scale

Developed in 1935, measure of strength of wave 100km from epicenter

Moment Magnitude Scale

Determined by area ruptured/amount of movement along fault, elasticity of crust at the focus

Strike-Slip Fault

Displacements are horizontal (San Andreas Fault)

Dip-Slip Faults

Displacements are vertical

Normal Fault

Hanging wall moved down relative to footwall

Reverse Fault

Hanging wall moved up relative to footwall inclined steeper than 45 degrees

Thrust Fault

Similar to reverse faults but angle is less than 45 degrees; strongest earthquakes

Tectonic Creep

Slow movement of rock/sediment along fracture caused by stress

P Waves

Primary/compressional waves, move fast w/ push-pull motion through solids/liquids

S Waves

Secondary/shear waves, move slowly in up down motion through solids

Surface Waves

Seismic waves forming when P & S waves reach Earth's surface; slower than body waves, responsible for damage near epicenter

Earthquake Shaking

Factors include magnitude, distance away, focal depth, direction of rupture; decreases with distance away from epicenter

Attenuation

Reduction of energy due to focal depth; seismic waves become less intense

Amplification

Increase in ground motion during an earthquake; P&S waves slow as they travel through alluvial sand/gravel etc.

Earthquake Cycle

Hypothesis explaining successive earthquakes on a fault; idea that strain drops abruptly after an earthquake and slowly accumulates until next one.

Stages of Earthquake Cycle

Inactive period, strain produces minor earthquakes, period of foreshocks (not always), mainshock occurs, aftershocks occur.

Intraplate Earthquakes

On fault in the interior, far from a plate boundary; considerable damage due to lack of preparedness, felt over large areas.

Primary Effects of Earthquakes

Ground shaking, surface rupture.

Secondary Effects of Earthquakes

Liquefaction, land-level change, landslides, fire, tsunamis.

Natural Service Functions of Earthquakes

Pathways for downward flow of surface water, new mineral resources, scenic landscapes.

Human Causes of Earthquakes

Weight from water reservoirs produced by dams creating faults, injecting liquid waste deep in the earth causes pressure, nuclear explosions may increase strain.

Precursors to Earthquakes

Pattern/frequency of earthquakes (foreshocks), land-level change over time, seismic gaps along faults, groundwater levels & rocks expanding.

Community Adjustments for Earthquakes

Critical facilities (hospitals) located safely away from faults, buildings must withstand vibrations, education, earthquake insurance.

Volcanoes

Located near plate boundaries, 2/3 found on 'Ring of Fire' in Pacific; subduction zones & mid-ocean ridges allow molten rock to reach surface.

Magma

Formed with silicon and oxygen, combined make silica; volcanic rocks named based on amount of silica (basalt, dacite, rhyolite).

Viscosity

Resistance to flow, volcano shapes based on chemistry and viscosity of magma.

Shield Volcanoes

Largest, shaped as broad arcs built from lava, basaltic magma, non-explosive gentle flows.

Composite Volcanoes

Cone shaped, built from lava and pyroclastic deposits, more dangerous/explosive but less frequent.

Volcanic Domes

Contain highly viscous rhyolite magma, step-sided mounts form around vents.

Cinder Cone Volcanoes

Small, made of tephra, round and contain crater at top.

Maars

Circular volcanic crater produced by explosive eruption and filled with water.

Ice-Contact Volcanoes

Erupt beneath/against glaciers, melt ice producing floods known as Jokulhlaups.

Crater

Depression formed by explosion of volcano at the top; 2km diameter.

Volcanic Vent

Opening on the surface where lava and pyroclastic debris erupt.

Caldera

Circular depression formed during collapse of volcano; can be 25km diameter.

Super Eruptions

Products of rare supervolcanoes, large volume of magma rises to shallow depths in continental crust.

Pahoehoe Lava

Low viscosity (few km per hour), high temp, when hardened it's smooth.

Aa Lava

High viscosity (few m per day), lower temp, when hardened texture is blocky.

Pyroclastic Flows

Avalanches of ash/gas/rock fragments that travel down slopes of volcano, speeds reach 150km/h.

Lahar

Large amounts of material saturated with water moving downslope (mudflows).

Radon

From natural decay of uranium in rock and soil; when inhaled it lodges in lungs damaging tissues.

Nuclear Meltdown

Results in damage when heat generated by reactor exceeds heat removed by cooling systems.

Groundwater

Found within cracks/spaces in soil, sand & rock; materials are permeable allowing water to flow through.

Formation of Solar System

Cloud of gas and dust in space was disturbed by a supernova 4.6b years ago.

K-T Boundary Mass Extinction

Occurred 65m years ago from abrupt cooling caused by asteroid impact; caused extinction of dinosaurs.

Avalanche

Mass of snow many m3 in volume separating from a snowpack flowing downslope.

Point-Release Avalanches

Begin as initial failure after heavy snowfall; sliding snow causes more failures in adjacent snowpack.

Slab Avalanches

Snowpack fractures along weak layer parallel to surface; moves as cohesive block, most dangerous.

Run-out Zone

Area of deceleration and snow deposition

Terrain Factors

Slope is most important; most occur between 25-60° (30-45° most dangerous)

Minimizing Risk

Buildings/roads located outside danger areas; buildings in danger areas require special engineering (reinforced walls/deflection structures)

Compression Test

Vertical force placed on top of snowpack to detect weak layers

Shovel Test

Assesses strength by isolating a column of snow & applying force on the uphill side

Rutschblock Test

Skier pushes & jumps on column of snow to detect cohesion of snowpack

Avalanche Cord

10m rope dragging behind person while skiing/snowboarding

Avalanche Transceiver

Portable device emits radio signal to assist in finding location of victim

Avalanche Dogs

Detect human scent rising through the snow & can cover large areas

Adaptation to Wildfires

Oak&Redwood bark resists fire damage; some pine seeds only open after fire

Elements of Wildfires

Requires fuel, oxygen & heat; plants that burn release CO2

Pre-Ignition

Vegetation reaches temperature at which it can ignite, while losing water

Combustion

Begins with ignition, occurs repeatedly as fire moves; not all ignitions result in fire

Flaming combustion

Rapid, high temp conversion of fuel into heat (flames)

Conduction

Transfer of heat by molecule to molecule contact

Radiation

Transfer of heat in form of invisible waves

Convection

Transfer of heat by movement of liquid or gas

Fuel

Includes leaves, wood debris, decaying material, etc. density of forest plays a role

Weather

Wildfires common after droughts, wind helps preheat materials & carry embers that ignite spot fires ahead of fire front

Surface Fires

Travel close to ground burning shrubs, leaves, etc. vary in intensity & very slow

Crown Fires

Move rapidly through forest canopy by flaming combustion; can be fed by surface fires, driven by strong winds & common in boreal forests

Effects of Wildfires

Leave behind layer that increases surface runoff and erosion for years; increase of airborne particles

Mountain Pine Beetle

Destroys forests throughout western Canada, consequences felt for decades; survives through winter in BC

Natural Service Functions

Reduces competition for sunlight/moisture in a forest, remove parasites in the soil, remove surface litter (leaves) allowing more moisture into soil

Fire Management

Control wildfires to benefit ecosystem but prevent harm to people/property; fire season is April-October, must research fire regime (potential of fire)

Fire Suppression

Steer fire toward area with no fuel (fire break) such as river, lake, road

Prescribed Burns

Controlled fires purposely ignited to reduce amount of fuel

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.

Disaster

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

Catastrophe

A massive disaster.

Magnitude-Frequency Concept

There is an inverse relationship between magnitude and frequency.

Tsunami

Thailand, December 2004.

Hurricane (Katrina)

New Orleans, August 2005.

Earthquake

Haiti, January 2010.

Oil Spill

Gulf of Mexico, April 2010.

Tectonic Cycle

This cycle involves the creation, movement, and destruction of tectonic plates.

Rock Cycle

Refers to a group of interrelated processes that produce the three different rock types: igneous, sedimentary, metamorphic.

Hydrologic Cycle

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

Hot Spots

Areas found away from plate boundaries where magma rises up from the mantle.

Divergent Plate Boundaries

At these boundaries, plates move away from each other, creating new land.

Convergent Plate Boundaries

At these boundaries, plates move toward each other, resulting in subduction zones.

Transform Boundaries

At these boundaries, plates slide horizontally past each other.

Acceptable Risk

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

Population Growth

Human population reached 7 billion in late 2011.

Human Footprint

The risks associated with hazards change as human development expands.

Infrastructure Failure

A hazard that poses a risk to both humans and the environment.

Ozone Depletion

A hazard that poses a risk to both humans and the environment.

Acid Rain

A hazard that poses a risk to both humans and the environment.

Nuclear Meltdowns

A hazard that poses a risk to both humans and the environment.

Toxic Gas Release

A hazard that poses a risk to both humans and the environment.