2.4 Impacts of Tectonic Hazards on Natural and Human Systems

How might tectonic hazards affect the natural and human systems?

How does ground shaking caused by Earthquakes affect the natural and human systems?

Occurs when

• seismic energy is released from an earthquake

  • causing violent vibrations on land

Impacts on Natural Systems

(a) Destroys ecosystems

• oil + chemical factories

  • ruptured

    → land + water pollution

• trees

  • uprooted

  • fractured

    → widespread tree injury + death

    → damages wildlife habitats

Impacts on Human Systems

(a) Destroys Properties and Infrastructure 

• buildings, bridges, roads, and railways

  • weakened 

      → collapse

  ∴ difficult to rescue people + supply emergency aid

(b) Causes Injuries and Fatalities 

• people may get trapped under 

  • collapsed infrastructure 

    → injuries + loss of lives 

(c) Disrupts Services 

• water + gas pipes 

  • snaps

    → water shortages

    → gas supply disrupted 

• electricity + communication cables 

  • break 

    → affects important communication services 

    i.e., tsunami warnings + tv broadcasts 

e.g., 2010 Christchurch, New Zealand earthquakes

• many trees damaged 

  • >300 trees removed 

    → reduces availability of habitats for wildlife 

How does landslides caused by Earthquakes affect the natural and human systems?

Occurs when

• violent ground vibration causes

  •  cracks on steep slopes

    → loosening the rocks and soil

  • then further shaking triggers the loose articles to

    → move downslope

Impacts on Natural Systems

(a) Destroys ecosystems

• fast-moving debris 

  • buries and destroys huge areas of 

    • forest

    • wetlands

• debris can enter and pollute 

  • rivers 

    → kills aquatic life

• rivers can be

  • blocked 

    → floods that damage nearby 

    • ecosystems

    • properties

       

Impacts on Human Systems

(a) Destroys Properties and Infrastructure 

• debris can 

  • bury 

  • destroy

    → properties + infrastructure 

(b) Causes Injuries and Fatalities 

• debris can

  • bury

  • hit

    people 

    → injuries + fatalities 

• debris can 

  • block rivers

    → floods 

    • drown people

(c) Disrupts Services 

• debris can

  • snap

→ electricity + communication cables and gas + water pipes

∴ disrupting the supply of these services

• debris can

  • block

    → roads + railways

∴ difficult to rescue people + supply emergency aid 

e.g., 2018 Papua New Guinea Earthquake (Mw 7.5)

• triggered landslides that caused 

  • huge amounts of debris to 

    → enter rivers 

    ∴ flooding 

    → polluting waters and killing marine life

• forests were destroyed

How does soil liquefaction caused by Earthquakes affect the natural and human systems?

Occurs when

• violent ground shaking causes

  • saturated

  • loose 

    soil to lose its soil structure 

    → transforming into a thick liquid 

Impacts on Natural Systems

(a) Destroys Ecosystems

• trees on liquefied soil may

  • sink and tip over

→ damages wildlife habitats

∴ forest + biodiversity loss

• liquefied soil may enter rivers 

  • smothers aquatic plants

∴ causing them to die 

• sewage pipes may be unbroken

  • untreated waste materials 

    • pollute rivers

∴ killing aquatic life

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• buildings and other infrastructure can

  • sink in and tip over

    → collapses

∴ difficult to rescue people and supply emergency aid

(b) Cause Injuries and Fatalities 

• people can get trapped in

  • collapsed infrastructure

    ∴ injuries + fatalities  

(c) Disrupts Services 

• electricity + communication cables and water + gas pipes

  • sinks in and snaps

    → disrupts supply of these services 

• roads and railways above liquefied soil

  • sink in and get damaged 

∴ difficult to rescue people and supply emergency aid

e.g., 2010 Christchurch, New Zealand earthquakes

• triggered severe soil liquefaction

• > 60,000 residential infrastructure (approx. 1/3 of the city)

  • were damaged

• liquefied soil entered

  • rivers

    +

• untreated sewage from 

  • broken pipes 

∴ polluted rivers

→ killed many aquatic species

How do tsunamis form?

1) An undersea earthquake causes the seabed to be

• displaced 

2) A large volume of water is lifted

• forms waves of

  • great wavelength 

  • low height (<1m)

3) Waves travel towards land at high speeds 

• 800km/h 

4) When approaching the coast

• greater friction with the shallower seabed

  • slow the waves 

5) Waves cluster together and increase in height 

• reach up to >15m height 

• travel at a speed of 30-50km/h

  → devastate shorelines hit by the waves 

6) Before a tsunami occurs

• The sea may recede from the shore

  • as the water fills the void caused by the 

    → displacement of the seabed

How does tsunamis caused by Earthquakes affect the natural and human systems?

Impacts on Natural Systems

(a) Destroys Ecosystems

• seawater

  • floods

→ huge areas of coastal wetlands + forests

∴ damages habitats

• large amounts of debris carried in by waves

  • pollute these areas

∴ damages ecosystems + kills wildlife 

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• fast-moving waters + large amounts of debris carried by the waves

  • sweeps away

    • buildings + infrastructure

∴ destroys them

(b) Cause Injuries and Fatalities 

• sweeping waters

  • drown people

• large amounts of debris carried by the waves

  • hit

  • kill

    → people

(c) Disrupts Services 

• fast-moving waters + large amounts of debris carried by the waves

  • snaps cables

    • communication + electricity

    → disrupts the supply of these services 

• fast-moving water

  • sweeps away

    • roads + railways

∴ difficult to rescue people and supply emergency aid

e.g., 2011 Tohoku Earthquake, Japan

• tsunami 

  • 40m tall

• waves carried debris inland

  • flooding

  • polluting

→ large areas of the land

• Sendai, a coastal city

  • suffered extensive damage

  • half of its population died 

• Iwate

  • 70k pine trees were knocked down

→ loss of forest + biodiversity

How does tephra caused by volcanic eruptions affect the natural and human systems?

Impacts on Natural Systems

(a) Destroys Ecosystems

• ash

  • carried by thousands of km by

    • prevailing winds 

→ pollutes forests, rivers + habitats 

∴ destroys ecosystems

• ash

  • suffocate + kill wildlife

  • cause blindness to birds

    → their eyelids get gummed together

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• volcanic bombs (a few cm - size of vehicles)

  • hit properties

→ damages them

• ashfall

  • accumulates on the roofs of buildings 

  • when saturated with water, ash’s weight doubles

    → roofs collapse

• ash

  • corrosive

→ weakens building structure 

∴ more susceptible to collapsing 

• thick blankets of ash

  • suffocates crops 

∴ damage farmland + destroys livelihoods

(b) Cause Injuries and Fatalities 

• volcanic bombs

  • hit people

→ injuries + fatalities

• ashfall causes

  • respiratory problems

  • eye irritation

  • suffocation

(c) Disrupts Services 

• ash particles can 

  • damage plane engines 

    → closure of airspaces 

∴ disruption of air transportation services

e.g., 1991 Mount Pinatubo Eruption, Philippines 

• emission of huge amounts of ash

• buried >180km2 of forests in

  • ash of 25cm

• destroyed 800km2 of rice fields

  • livelihoods of many farmers affected

• 7 airports had to close down + many flights cancelled

  • disruption of transport

• some planes → damaged

How does volcanic gases caused by volcanic eruptions affect the natural and human systems?

Characteristics

• releases large amounts of toxic gases 

  • sulfur dioxide 

  • carbon dioxide

Impacts on Natural Systems

(a) Destroys Ecosystems

• when sulfur dioxide reacts with water in the air 

  • acid rain 

→ damages vegetation + soil + kill wildlife 

• cold carbon dioxide is concentrated in 

  • low-lying volcanic areas 

    → as it is heavier than air 

∴ abundance of carbon dioxide

→ kills wildlife + soil + destroys vegetation

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• sulfur dioxide causes

  • acid rain

→ corrodes infrastructure

(b) Causes Injuries and Fatalities and Threatens Public Health

• sulfur dioxide irritates

  • skin

  • eyes

  • nose

  • throat

• air with >3% carbon dioxide causes

  • headaches

  • breathing difficulties

  • even death when it exceeds 15%

e.g., 1979 Dieng Volcano Eruption, Indonesia

• released deadly amounts of CO2

  • killed about 150 people

How do lava flows caused by volcanic eruptions affect the natural and human systems?

Characteristics

• extremely hot 

• travel some distances within the volcano it originated from

• deaths caused directly by lava flows are

  • uncommon 

    → people can easily move outta the way 

Impacts on Natural Systems

(a) Destroys Ecosystems

• hot, low-silica lava 

  • travel some distances 

∴ destroys forests + habitats + ecosystems in them

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• lava burns through

  • homes

  • infrastructure etc.

(b) Cause Injuries and Fatalities 

• indirect death via

  • destruction of homes

    → lava burning through

• deaths are uncommon

  → easy to move out of the lava’s way

(c) Disrupts Services 

• lava destroys

  • communication + electricity cables

  • water + gas pipes

→ disrupts the supply of these services

e.g., 2018 Kilauea Eruption in Hawaii

• far-reaching lava flows destroyed

  • >600 homes

  • forests + ecosystems 

• telephone + power lines

  • damaged

    → widepread communication outages 

How do pyroclastic flows caused by volcanic eruptions affect the natural and human systems?

Characteristics

• hot cloud of 

  • gas

  • ash

  • rocks

→ travelling down the slopes of a volcano at high speeds (200km/h)

• temperature of up to 700 degrees Celsius 

  • Perhaps the most devastating volcanic hazard

Impacts on Natural Systems

(a) Destroys Ecosystems

• huge areas of forests

  • destroyed

∴ biodiversity loss

• thick layers of ash

  • cover the path of the flows 

∴ pollutes huge areas of forests

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• hot flows burn

  • everything in their path

∴ destroying any infrastructure in its way

(b) Cause Injuries and Fatalities and Threatens Public Health

• extreme temperatures

  • burn

  • kill

→ people in a fraction of a second

(c) Disrupts Services 

• hot flows

  • destroys

→ electricity + communication cables and water + gas pipes

∴ difficult to rescue people and supply emergency aid

e.g., 2010 Merapi Eruption, Indonesia

• 350 people killed

  • mostly due to burns + blast injuries 

• huge areas of forests were burnt

How do lahars caused by volcanic eruptions affect the natural and human systems?

Characteristics 

• mudflows

  • comprising of water + volcanic ash

• formed when ash + rocks ejected during an eruption

  • mix with water

• occurs when 

  • intense rainfall washes down the ash

  • pyroclastic flows melt snow + ice

    → mixes with water on the volcanic cone as they travel down

Impacts on Natural Systems

(a) Destroys Ecosystems

• lahars can cover

  • forests

  • ecosystems

→ with thick mud that hardens like concrete

∴ destroying them

• lahars can 

  • pollute rivers

→ kills aquatic life

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• lahars

  • buries

  • destroys

→ houses

• lahars can cover

  • farms

→ with thick mud that hardens like concrete 

∴ destroys them

(b) Cause Injuries and Fatalities and Threatens Public Health

• lahars can bury

  • houses and

  • its residents

∴ killing them

(c) Disrupts Services 

• lahars can damage

  • communication + electrical cables

  • water + gas pipes

→ disrupts the supply of these services

• lahars can block

  • railways + roads

∴ difficult to rescue people and supply emergency aid

e.g., 2010 Mount Merapi Eruption, Indonesia 

• Heavy rain occurred on November 4th

  • lahars 

    → flowed into towns 

    → destroyed bridges

How do volcanic landslides caused by volcanic eruptions affect the natural and human systems?

Impacts on Natural Systems

(a) Destroys Ecosystems

• fast-moving debris

  • buries

  • destroys

→ huge areas of forests + wetlands

• debris from landslides 

  • pollutes rivers

  • blocks rivers 

∴ kills aquatic life + causes floods 

→ damages properties + ecosystems

Impacts on Human Systems

(a) Destroys Properties and Infrastructure

• debris 

  • buries 

  • destroys

→ infrastructure + properties

(b) Cause Injuries and Fatalities 

• debris

  • bury

  • hit 

→ people 

∴ injuries + fatalities

• debris blocks rivers

  • floods 

→ drowns people

(c) Disrupts Services 

• electricity + communication cables and water + gas pipes

  • snapped by debris

    → disrupts the supply of these services 

• roads and railways

  • blocked by debris

∴ difficult to rescue people and supply emergency aid

e.g., 1980 Mt St Helens Eruption, USA

• triggered volcanic landslides 

  • traveled as far as 23km away from its origin

• destroyed huge areas of land

  • killing many wildlife

What are the benefits of living near volcanoes and volcanic eruptions?

volcanic eruption provides

• fertile soil for farming after volcanic materials are broken down and weathered

• and makes available valuable minerals and building materials

living near volcanoes allows harnessing

• of geothermal energy and

• tourism activities

Farming with Fertile Soil

over thousands of years

• volcanic rocks

  → break down + undergo weathering

∴ forms fertile soils

• suitable for agriculture

  • produces a higher crop yield

∴ locals benefit → earn more revenue

                          and grow a larger variety of crops

e.g., Indonesia

• best rice-growing regions located near volcanoes 

  • Bali → several volcanoes like Mount Agung

Extracting Precious Minerals and Fossil Fuels

some magma may cool and solidify beneath volcanoes

• forms precious minerals

  → copper, silver, gold

• locals living near volcanoes can be

  • employed to mine these minerals

→ providing locals with a source of income

• governments may sell the minerals

  • generate revenue

→ can fund social services for locals (education+healthcare)

• volcanic materials like ash + sand

  • may be mined 

→ used as construction materials

e.g., Mount Merapi, Indonesia

• thousands of locals living there are

  • employed to mine volcanic sand

→ as it is suitable for constructing buildings

Harnessing Geothermal Energy

geothermal energy is derived from heat in 

• Earth’s crust 

it can be harnessed in tectonically active areas 

• beneath Earth’s surface

  • hot rocks heat groundwater

    → steam formed is harnessed 

    • generates electricity 

∴ locals benefit from cheaper electricity 

• produced locally 

→ locals can also be employed to work in

• geothermal power plants

e.g., Iceland

• majority of its electricity is generated from

  • geothermal power

→ due to the many volcanoes in the country

Tourism Activities 

tectonic environments

• attracts tourists 

• tourists can engage in many activities

  • hiking

  • sightseeing

Tourism provides locals with employment opportunities 

• tour guides

• food vendors

• souvenir seller

• homestays

∴ boosts local economic development

e.g., Hawaiian Islands

• popular tourist destination for its

  • scenic volcanic landscapes 

→ tourism generates an annual income of US$88mil

• provides locals with thousands of jobs