Physical Geography - Hazardous Environments

Hazard

A threat that has potential to harm people and the environment

Disaster

A hazard that causes fatalities or extensive financial damage

Risk

The exposure of people to a hazard

Vulnerability

The degree to which conditions make the population less likely to cope or recover from the hazard

Resilience

How well people can recover from a hazard

Geo-Physical Hazard

A potential natural phenomenon that can cause damage to humans and the environment

Disaster Hotspot

A location which is at risk of experiencing two or more geophysical hazards (multi-hazard environment)

Converging Destructive Plate Boundary (C/O)

Example: Nazca and South American Plates

Landforms: Fold mountains (Andes), Ocean Trenches (Peru-Chile), Composite Volcanoes (Misti)

Converging Destructive Plate Boundary (O/O)

Example: Pacific and Philippines Plates

Landforms: Deep Sea Trenches (Mariana Trench) and Island arc (Mariana Island Arc), Composite Volcanoes

Diverging Constructive Plate Boundary

Example: North American and Eurasian Plates

Landforms: North Atlantic Mid Ocean Ridge, Shield Volcanoes

Collision Plate Boundary

Example: Indian and Eurasian Plates

Landforms: Fold Mountains (Himalayas)

Hotspot - Intraplate (O)

Example: Ring of Fire (Pacific)

Landforms: Shield Volcanoes, Volcanic Island Arcs (Hawaii)

Hotspots - Intraplate (C)

Example: African Plate (EARV)

Landforms: Shield Volcanoes (East African Rift Valley)

Conservative Plate Boundary

Example: North American and Pacific Plates (San Andreas Fault)

Landforms: Steep slopes and long cliffs, faulting, escarpments

Epicentre

The main area above ground that is hit by the earthquake

Focus

The point underground where the earthquake originates

Seismic Waves

Waves of energy which create the earthquake

P-Waves (Body)

First waves recorded on a seismograph

Travel through the rock, gas, and liquid as waves of compression (back and forth)

Fastest to travel

S-Waves (Body)

Second waves recorded on a seismograph

 

Flows more slowly with a rolling motion, passing through solids only

Love Waves (Surface)

Lateral shaking

Combined, they are undulated rolling waves

Raleigh Waves (Surface)

Vertical waves

Combined, they are undulated rolling waves

Richter Scale

• Logarithmic scale that uses numbers (1-10) 2 is 10x more powerful than 1, 3 is 100x more etc.

• Objective scale recorded via seismograph

• Measures size/intensity of the event

• Measures from the focus

Mercalli Scale

• Subjective scale based on perception

• Each level is a description of impacts

• Measures levels from 1-12

• Measures from the epicentre

8 Factors affecting the strength of earthquake damage

Population Density

Rock Type and Sediment

Economic Development

Types of Buildings

Epicentre Distance

Strength, Depth, Number of Aftershocks

Time of Day

Secondary Hazards

Population Density (Factor affecting earthquake strength)

• The number of people exposed to the hazard e.g. Haiti, Port-au-Prince.

Rock Type + Sediment (Factor affecting earthquake strength)

• Bedrock properties

• Slope/areas prone to liquefaction

Economic Development (Factor affecting earthquake strength)

• HIC vs LIC

• Preparedness, levels of protection

• Early warning systems

• Ability to rebound after the event 

Types of Building (Factor affecting earthquake strength)

• Varying levels of protection

• Building standards/materials used

• Heights of buildings

Epicentre Distance (Factor affecting earthquake strength)

• Populations exposed to risks

• Waves impact infrastructure, etc.

Strength, Depth, and Aftershocks (Factor affecting earthquake strength)

• Deeper earthquakes mean that waves have to travel further and aren't as bad

Time of day (Factor affecting earthquake strength)

• Response time is slower at night

Primary Hazards of an earthquake

Ground Shaking

Ground Fracture/rupture

Secondary Hazards of an earthquake

Tsunamis

Fires

Aftershocks

Building collapse

Mass movements

Soil liquefaction

Spread of disease

Soil Liquefaction

Soil liquefaction is the violent shaking of the ground, making relatively solid material such as rock and clays become unconsolidated (Christchurch, New Zealand, 2010)

Landslides Avalanches - Gorkha, Nepal, 2015 CASE STUDY: Setting and Causes

Setting: It had a magnitude of 7.8 and occurred about 80km northwest of Kathmandu. Shallow earthquake with focus approx. 8km down

Causes: It was caused by a release of built up stress along a fault line between the Indian and Eurasian plates creating an earthquake

Landslides Avalanches - Gorkha, Nepal, 2015 CASE STUDY: Primary and Secondary Impacts

Primary: Major Earthquakes

Secondary: Several avalanches triggered on Mt. Everest, killing at least 19 people and over 250 in Langtang Valley

Hundreds of thousands made homeless

Landslides Avalanches - Gorkha, Nepal, 2015 CASE STUDY: Short and Long-Term Responses

Short Term: 90% of the Nepalese army helped with rescue

Long Term: Rebuilding the Economy - Over $5 billion

The Tohoku (Sendai) Tsunami, Japan, 2011 CASE STUDY: Setting and Causes

Setting: March 2011, Japan

Earthquake + Tsunami

Causes: A 9.0 earthquake occurred under the Pacific Ocean 100km due east of Sendai on northern Honshu's eastern coast

 A 400-500km segment of the North American plate was being dragged down by the Pacific plate and suddenly slipped out

The Tohoku (Sendai) Tsunami, Japan, 2011 CASE STUDY: Primary and Secondary Impacts

Primary: Ground shaking

Secondary:

Collapsing buildings

Half a million people homeless

Over 1 million homes without running water

Food shortages

The Tohoku (Sendai) Tsunami, Japan, 2011 CASE STUDY: Short and Long-Term Responses

Short Term:

International recovery teams

People being evacuated

Long Term:

Schemes set up to plan long-term growth (Reconstruction Design Council)

More effective planning of defenses for the future

How is a Tsunami Created

A submarine earthquake thrusts a plate upwards, displacing a column of water.

The column rises and sinks, creating a ripple of small waves, with low height but long length of 100 miles, in all directions.

The wave travels very fast, 500 mph, and approaching shallow land slows, until the wave length catches up, with the wave getting taller and taller.

Christchurch, New Zealand, 2010/11 Earthquake CASE STUDY: Setting and Causes

Setting:

2010 earthquake -> Saturday morning (4:35 am).

2011 earthquake -> Tuesday lunchtime.

On the Australian and Pacific plate boundary

Causes:

Earthquakes result from deformation along different thrust faults at the destructive plate boundary where the Pacific plate subducts beneath the Australian plates. Focus was no deeper than 5km

Christchurch, New Zealand, 2010/11 Earthquake CASE STUDY: Primary and Secondary Impacts

Primary Impacts:

Vertical and horizontal shaking 

Major tremors 

Secondary Impacts:

Vertical and horizontal shaking at the same time destroyed 100 major buildings 

Shaking = 4x more intense than Haiti 

Liquefaction undermined the foundations of many buildings 

Numerous aftershocks made recovery difficult 

Water and sewerage systems were damaged and power cuts affect homes. 

Liquefaction forced road surfaces upwards, slowing rescue efforts 

$US 40 billions - rebuilding and insurance 

Christchurch, New Zealand, 2010/11 Earthquake CASE STUDY: Short and Long-Term Responses

Short-Term:

Electricity and mains water supplies were repaired quickly. 

Fully serviced mobile homes housed the homeless until the repairs were finished. 

Many services were restored within a week 

The international airport was undamaged, overseas aid was sent quickly

Long-Term:

Buildings were rebuilt to withstand earthquakes with a minimum height of 28 metres

Earlier planning for emergencies, so all forces can come together quickly and work together

Haiti, Port au Prince, 2012 Earthquake CASE STUDY: Setting and Causes

Setting: January 12th at 4:53 am, epicentre 25km from the city of Port au Prince, western Haiti, 7 on the Richter scale

Causes: Tiny fragment of the Caribbean plate moving eastwards along a fault line on the destructive plate boundary with the North American plate. The shallow depth of movement caused much damage from shaking, which lasted for nearly a minute.

Haiti, Port au Prince, 2012 Earthquake CASE STUDY: Primary and Secondary Impacts

Primary Impacts:

200,000 to 316,000 deaths

100,000 injured

Buildings falling on people

Houses destroyed

Water and food sources were disrupted

Power lines disrupted

Secondary Impacts:

1.5 million homeless

Hospitals and government buildings were destroyed

Looting and violence were a problem for relief workers trying to keep stocks of food and water safe

Disease outbreak - cholera outbreaks caused by poor sanitation in the temporary tented camps

The international airport only had one runway, limiting planes carrying aid

Many rebuilt buildings collapsed after the earthquake as they were constructed cheaply and had little support

Haiti, Port au Prince, 2012 Earthquake CASE STUDY: Short and Long-Term Responses

Short Term:

Largely dependent on overseas aid (medical aid + financial aid)

Temporary accommodation/emergency shelter

IMF potentially gave money/economic aid

Bottled water + purification tablets + food packages

Search + rescue teams

Long Term:

Clearing up the rubble

Rehoming into temporary accommodation (280,000 still without permanent housing after 3 years)

Infrastructural projects/rebuilding main cost

Reducing the new unemployment rate by creating more factories

Kick-starting the economy again

Hazard Management Cycle

Preparedness (Before the event) → Response (During event) → Recovery (Straight after event) → Mitigation (Long after the event)

Park Model

Stage 1 of the model is what normal day-to-day life is like in an area, involving quality of life, economic activity, and social stability before the event takes place

Stage 2 of this model is the start of this hazardous event and sees the deterioration from normality, the extent of which can vary depending on the preparedness of each certain area

Stage 3 involves search and rescue of the event, for example, saving people from rubble, etc.

Stage 4 is the relief period of the event, which may include outside help (the World bank)

Stage 5 is a return to normality (or as close as possible) as some countries such as Haiti will never return to what they once were, decreasing their actual normality

Degg Model

The Degg Model shows that a natural disaster only occurs if a vulnerable population is exposed to a hazard

The 3 P’s

Prediction

• Seismic gap theory

• Monitoring of earthquake zones

• Hazard mapping

Preparedness

• Community Education

• Home Safety Improvements

• Warning Systems

Protection

• Strengthening buildings

• Safe Houses

• Land-use zoning

Landslides Case Study

Gorkha, Nepal, 2015

Tsunamis Case Study

Sendai, Japan, 2011 (15,000 deaths with warning system)

Boxing Day, Indonesia, Bandah Aceh, 2005 (250,000 deaths with no warning system)

LIC Case Study

Haiti, Port au Prince, 2012

HIC Case Study (Soil Liquefaction)

Christchurch, New Zealand, 2010

Seismic Gap Theory Case Study

San Francisco 1989

Monitoring of Earthquakes Case Study

Parkfield California 1992 → Unsuccessful

New Zealand’s Earthquake Commission did predict in 1991 there would be an earthquake in Christchurch (but could not say when or what intensity but knew liquefaction would occur)

Hazard Mapping Case Study

California, San Andreas Fault - 150m radius of known faults

Hazards Awareness Day Case Study

Japan on the 1^st of September annually

Evacuation points, survival packs, house improvements and warning signs Case Study

Places around Japan

Strengthening Buildings Case Study

HIC – TransAmerican Pyramid in San Francisco, USA withstood the 1989 Loma Prieta earthquake, magnitude 7, with its shock absorbers and swinging building

HIC – Bird’s Nest, Beijing, China Olympic Games 2008, made of two parts

LIC – Confined masonry in Haiti new builds post-2010, or adding wire mesh to adobe clay structures such as Peru

Safe Houses Case Study

New strict codes in Indonesia

Land use zoning Case Study

Christchurch, Japan, Most HICs

What is a Volcano

A volcano is an opening in the earth's crust where magma (a mixture of red hot liquid rock, mineral crystals, rock fragments, and dissolved gasses) erupts onto the earths surface

Shield Volcanoes

Gently sloping sides, large base

Effusive

Basaltic lava

Formed by low-viscosity lava

Diverging constructive margins

1-2 VEI

MAR/Hawaii

Thin part of the lithosphere

Magma rises due to plates moving because of convection currents

As the plate moves, volcanoes are formed, forming island arcs and creating a long chain of extinct volcanoes

Composite Volcanoes

Subduction due to a denser plate being pulled down

Multiple layers of material (composite)

When the plate subducts into the mantle, it melts

Magma rises towards the surface and erupts if it doesn’t cool in time, causing a composite volcano

Lower temperature, cools much quicker, forming steeper sides

Andesitic lava

Ash plumes add onto the sides, hardening and steepening the sides

Nazca - South American -> Volcano Misti

Caldera Volcano (Super)

Characterised by a depression in the ground with a caldera rim

Rhyolitic, lots of tephra

Close to the magma chamber

Caldera can be 50 miles across

Super volcanoes explode at a VEI of 8

Flood Basalt Provinces (Lava plateau)

Very-large-scale hotspot -> travels a great distance

Larger mantle plume across a bigger landscape

Lava floods the ground

Coating the landscape in lava

Decan Traps (India)

Fissure Eruptions

Faults or cracks within the earth’s crust and magma flow up through this crust and effusively leak onto the ground.

Icelandic, VEI 0-2, Basaltic, High lava temp

Reykjanes peninsula

Cinder Cone

Steep slopes with wide craters

It might not have any side vents or parasitic vents, unlike composite

Single main vent

Taal volcano in the Philippines 

Lava Dome

Magma has not broken through the surface

Magma continues to expand as it is less dense

Endogenous is when magma stays within the bubble under the crust

Exogenous is when magma breaks through the dome

Slate Mountain, San Francisco

Effusive Eruptions

Lava Type: Basaltic

Mineral Composition: Mafic (Magnesium + Iron)

Silica Content %: <50%

Viscosity: Low

Temperature: 1200C

Eruption Type: Icelandic or Hawaiian

VEI: 1-2

Volume of Material Ejected: 0.0001km³

Volcano Types: Lava plateau, Fissure, or Shield

Inter (Intra) Boundary Type: Diverging Constructive

Landforms: Mid-Ocean Ridge

Example: North American and Eurasian Plate Boundary

Explosive (Andesitic) Eruptions

Lava Type: Andesitic

Mineral Composition: Mixed

Silica Content %: 60%

Viscosity: Intermediate

Temperature: 1000C

Eruption Type: Vulcanian or Vesuvian

VEI: 3-4

Volume of Material Ejected: 0.1km³

Volcano Types: Composite or Cinder Cone

Inter (Intra) Boundary Type: Converging Destructive

Landforms: Trenches, Fold Mountains, Volcanoes

Example: Nazca and South American Plate Boundary

Explosive (Rhyolitic) Eruptions

Lava Type: Rhyolitic

Mineral Composition: Felsic (silicon, oxygen, aluminium, sodium, and potassium)

Silica Content %: >70%

Viscosity: High

Temperature: 800C

Eruption Type: Plinian or Pelean

VEI: 5-8

Volume of Material Ejected: >1000km³

Volcano Types: Lava Dome, Caldera Super Volcano

Inter (Intra) Boundary Type: Converging Destructive

Landforms: Trenches, Fold Mountains, Volcanoes (Super)

Example: Philippines and Pacific Plate Boundary

VEI

Volcanic explosivity index

1 - 8 (1 includes smaller ranges of tephra - 8 is larger size/volume)

Explosion Range

Icelandic (effusive) - Plinian (Most explosive)

Volume of ash cloud/size of ash cloud increases as you move through scale

Earthquakes (Primary Hazard of Volcanoes)

The shaking of the ground due to energy/pressure release

Seismic activity through magma travelling through side vent

E.g. Vesuvius

Gases (Primary Hazard of Volcanoes)

Sulphur and Carbon dioxide released into atmosphere (Toxic)

E.g. Lake Nyos, Cameroon

Lava (Primary Hazard of Volcanoes)

A’a- Develops rigid block-like structures

Pahoehoe - Pillow-like, lower silica content - more basaltic

Hawaii vs. Mt. St. Helens

Solids (Primary Hazard of Volcanoes)

Tephra is any airborne solids

Ash, cinders, lapilli, volcanic blocks, volcanic bombs

E.g. Super Calderas and Strato-Cones (Composite)

Pyroclastic Flows (Primary Hazard of Volcanoes)

Very hot (800-1500C) gas charged, high velocity flows (up to 200 mph) made from a mixture of gases and tephra

E.g. Composite volcanoes

Atmospheric Ash Fallout (Secondary Impact of Volcanoes)

Big ash clouds get trapped in the earth’s atmosphere and can spread over big distances

E.g. Eyjafjallajokul 2010, Ash closed European airspace for 1 month

Lahars (Secondary Impact of Volcanoes)

Moving flow of mud, any material that has been carried through a lava melt and potentially snow melt

E.g. The Nevado del Ruiz volcano, in the Andes.

Lahars 50 M thick travelled at 60km per hour down existing river valleys 

Acid Rainfall (Secondary Impact of Volcanoes)

Volcanic eruptions release sulphur dioxide gas from both lava flows and from violent eruptions. These gases can pollute the air and result in the formation of acid rain

E.g. Hunga Tonga-Hunga Ha'apai Volcano, sending plumes 18 km into the air

CASE STUDY: Primary Effects, Lake Nyos, Cameroon 1986 – Volcanic Gases

Location: Lake Nyos, Cameroon, is located just north of the equator in West Africa.

Type of Volcano: Created by deep crater lakes on top of a volcano within the Oku Volcanic Field

Description of events: Huge volumes of volcanic gas came bubbling up through and came down the side into the valley and a town. This happened because carbon dioxide is heavier and denser than oxygen; therefore, it stayed on the ground. It happened on the 21st of August 1986

Effects: It suffocated around 1700 people and 3000 cattle, however, plants were unaffected.

CASE STUDY: Secondary Effects, Nevada del Ruiz, Colombia, 1985 – Lahars

Location: Nevada del Ruiz is a volcano in Colombia that rises to an altitude of 5400 metres and is covered by an icecap 30 metres thick, covering an area of about 20km²

Type of Volcano: Subducting oceanic Nazca plate and the continental South American plate

Description of events: The volcano erupted in 1986, causing the ice to melt from the heat. This condensing volcanic steam, ice-melt and pyroclastic flows combined to form lahars that moved down the mountain, engulfing the village of Chinchina.

Effects: This killed 1800 people and destroyed the village. The conditions worsened as further eruptions melted more ice, creating larger lahars that were capable of traveling further down the mountain into the floodplain of the Rio Magdalemna.

Predicting Eyjafjallajokull, 2010 - How are the Volcanoes being monitored?

Infrasound devices around Iceland (4)

Infrasound detects pressure variations from volcanic eruptions

Waterflow centres and electro radars

Ash measurements to help aerospace

Seismic recordings

Data analysed at IMO 24/7

Volcanoes are monitored prior to, during, and after events

How to Manage Volcanoes

Prediction:

• Changes in ground

• Geochemical Changes

Mitigation:

• Control minimisation

• Hazard mapping

• Building structures

Forecast

• Frequency Forecasting

Harmonic Tremors (Prediction)

Earthquakes provide very strong evidence of an impending eruption

e.g. Mt St Helen's, 1980

Ground Deformation (Prediction)

Bulging can be detected by rising magma, measured using an instrument called a tiltmeter

e.g. Mt St Helen’s, 1980

Satellite Monitoring (Prediction)

Cameras set up allow remote viewing of volcanoes allowing scientists to see small signs

e.g. Mt St Helen’s

Geochemical, gravitational and temperature changes (Prediction)

Instruments can be used to study the physical properties associated with rising magma.

Hydrology and gases changes (Prediction)

Changes in physical and chemical properties in water such as rising temps

Measuring volumes of gas such as sulphur dioxide

e.g. Pinatubo, 1991

Control Minimisation (Mitigation)

Cooling/diverting lava flows with water on a mass scale as well as explosive

Issuing warnings

Evacuation safe zone

e.g. Mt Eldfell, 1973, Mona Loa, ongoing, Mt Etna, 1992

Hazard Mapping (Mitigation)

Can develop risk assessments for vulnerable populations

Using past evidence to see who is most at risk

e.g. Monserrat

Building Structures (Mitigation)

Concrete shelters

Diversion channels

Evacuation routes

Air monitoring

Boreholes

Trenches

Hot springs

Frequency Forecasting (Forecasting)

Similar to flood events, one can look at the frequency of historic eruptions to get a sense of when the pressure has built to the extent of an eruption.

e.g. Yellowstone Supervolcano has a frequency of around 725,000

Impacts of mass movements

Primary

• Movement of sediment

• Rockfall

• Destruction

• Agricultural degradation

• Fatalities

 Secondary

• Rebuilding projects

• Impacts on education

• Hits to economic development

• Disruption on transport routes for a long time

The Bingham Copper Mine Landslide and Rockfall, Salt Lake City, Utah, USA, April 2013 CASE STUDY: Background

Setting: Located in Bingham, Utah, USA and it occurred on the 10th of April 2013

Type of mass movement: Rock avalanches

The Bingham Copper Mine Landslide and Rockfall, Salt Lake City, Utah, USA, April 2013 CASE STUDY: Causes and Impacts

Causes: Overmining, decreasing internal resistance, causing rocks to break

Primary Impacts: Two main slides, Roads around the mine are blocked, Infrastructure blocked

Secondary Impacts: Rockfall triggered 19 smaller earthquakes, Economic disruption the area, A second slide