Tectonics Topic 2.4 (impacts of tectonic hazards on natural and human systems)

earthquake hazards :

1. ground shaking

2. soil liquefaction

3. landslides

4. tsunamis

volcanic hazards :

1. tephra

2. volcanic gases

3. lava flows

4. pyroclastic flows

5. lahars

6. volcanic landslides

impact on natural and human systems

1. destroy ecosystem (natural system)

2. destroy properties and infrastructure (human systems)

3. disrupts services (human systems)

4. causes injuries and fatalities (human systems)

ground shaking : destroys ecosystems

• Ruptures oil and chemical factories, polluting land and water

• Fractures and uproot trees, causing widespread tree injury and death and damages wildlife habitats

ground shaking : destroys properties and infrastructure

Weakens buildings, bridges, roads and railways, causing them to collapse, making it difficult to rescue people or supply energy aid

ground shaking : disrupts services

• Snaps water and gas pipes, resulting in water shortages and disruptions to gas supply 

• Electricity and communication cables break, affecting important communication services such as tsunami warnings and television broadcasts

ground shaking : causes injuries and fatalities

People may get trapped under collapsed buildings and infrastructure, resulting in loss of lives and injuries

ground shaking : example

• 2010 Haiti earthquake (mW 7.0) : surrounding areas around factories were polluted → debris polluted rivers. More than 220k people were killed and water pipes ruptured, causing water shortages

• 2010 Christchurch New Zealand earthquakes : may trees were damaged and more than  300 had to be removed, reducing availability of habitats for terrestrial species

soil liquefaction : destroys ecosystem

• Trees on liquefied soil sink in and tip over, damaging wildlife habitats, causing forest and biodiversity loss

• Liquefied soil may enter rivers and smother aquatic plants, causing them to die 

• Sewage pipes may be broken and untreated waste materials may pollute rivers, killing aquatic species 

soil liquefaction : destroys properties and infrastructure

• Buildings and other infrastructure can sink in and tip over, and the damage makes it difficult to rescue people or supply emergency aid

soil liquefaction : disrupts services

• Electricity and communication cables, and water and gas pipes can sink in and snap, disrupting supply of these services

• Roads and railways above liquefied soil can sink in and get damaged, making it difficult to rescue people or supply emergency aid

soil liquefaction : causes injuries and fatalities

People can get trapped under collapsed buildings and infrastructure, resulting in injury and loss of lives

soil liquefaction : example

2010-2011 Christchurch New Zealand earthquakes: triggered severe liquefaction as the city lies on a former swamp where soils are loose and saturated. More than 60k residential buildings and infrastructure covering about one third of the city area were damaged. Liquefied soil entered rivers, and untreated sewage from broken pipes polluted rivers which resulted in the reduction of some species such as the caddisflies

landslides : destroys ecosystems

• Fast moving debris can bury huge areas of forests and wetlands

• Rivers can be polluted with debris, killing aquatic life

• Rivers can be blocked, causing floods that can damage nearby ecosystems and properties

landslides : destroys properties and infrastructure

Debris can bury villages and farms, destroying properties and infrastructure

landslides : disrupts services

• Debris can snap electricity and communication cables, and water and gas pipes, disrupting supply of these services

• Roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid 

landslides : causes injuries and fatalities

• Debris can bury people or hit them, causing injuries and loss of lives

• Debris can block rivers, resulting in food, which can drown people. 

landslides : examples

• 2008 Great Sichuan China Earthquake (Mw 7.9) : triggered more than 15k landslides, destroyed many buildings and infrastructure and caused nearly 20k deaths. 

• 2018 Papua New Guinea earthquake (Mw7.5) : triggered landslides that caused huge amounts of debris to enter rivers which caused floodings, destroyed forests and polluted waters, killing fish

tsunamis

a series of ocean waves which can be caused by undersea earthquakes

tsunamis occur when …

1. An undersea earthquake causes the seabed to be displaced

2. A large volume of water is lifted, forming waves of great wavelength and low height of less than 1m

3. The waves travel towards land at high speeds around 800km/h

4. On approaching the coats, greater friction with the shallower seabed slows the waves down

5. Waves get close together and increase in height of 15m or more, travelling at a speed of 

6. 30-50km/h and devastate shorelines the waves hit

7. Before a tsunami occurs, the sea may recede from the shore because the sea water fills in the void caused by displacement of seabed

tsunami : destroys ecosystems

• Seawater can flood huge areas of coastal wetlands and forests, damaging habitats

• Large amounts of debris carried in by the waves can pollute these areas, damaging ecosystems and killing wildlife 

tsunami : destroy properties and infrastructure

Fast moving waters and the large amounts of debris carried in by the waves can sweep away buildings and infrastructure, destroying them

tsunami : disrupts services

• Fast moving waters and the large amount of debris carried in by the waves can snap electricity and communication cables, disrupting supply of these services

• Fast moving water can sweep away roads and railways, making it difficult to rescue people or supply emergency aid

tsunami : causes injuries and fatalities

• Sweeping waters can drown people

• Large amounts of debris carried in by the waves can hit and kill people

tsunami : examples

• 2004 indian ocean tsunami : triggered by a 9.1 Mw undersea earthquake near Sumatra, Indonesia. Tsunami waves slammed into the coasts of 11 indian ocean countries from indo to somalia in africa. More than 230k killed and entire coastlines and habitats were destroyed

• 2011 Tohoku Japan earthquake (Mw 9.0) : triggered a 40m high tsunami which destroyed homes and infrastructure. Tsunami waves carried debris inland, flooding and polluting large areas of land. The coastal city of Sendai suffered extensive damage and half of its population was killed. In Iwate, 70k pine trees were knocked down, resulting in forest and biodiversity loss. Tsunami hit pacific islands, devastating the ecosystem. Entire bird nesting sites were lost and more than 100k Layson Albatross chicks were killed and thousands of fish were washed ashore where they suffocated.

tephra : destroys ecosystem

• Ash can be carried thousands of km by prevailing winds, polluting huge areas of forests, rivers and other habitats and destroying ecosystem

• Ash can suffocate and kill wildlife

• Ash can cause blindness to birds, with their eyes getting gummed together 

tephra : destroys properties and infrastructure

• Volcanic bombs, ranging from a few cm to the size of vehicles, can hit properties, damaging them

• Ashfall can accumulate on roofs of buildings

• When saturated with water, the weight of ash can double, causing buildings roofs to collapse

• Being corrosive, ash weekends building structures, making them more likely to collapse 

• Thick blankets of ash can damage farmland, suffocating crops and destroying livelihoods

tephra : disrupts services

Ash particles can damage plane engines, leading to closure of airspaces and disrupting air transportation services

tephra : causes injuries and fatalities

• Volcanic bombs can hit people, causing injuries and loss of lives

• Ashfall can cause respiratory problems, eye irritation and suffocate people

tephra : example

1991 mount pinatubo eruption in the philippines that emitted huge amounts of ash and buried more than 180km2 of forest in ash of about 25cm thick. Destroyed 800km2 of rice fields, affecting livelihoods of farmers. Seven airports in Philippines had to close and many flights were cancelled, disrupting transport. Some planes were also damaged. 

volcanic gases : destroys ecosystems

• Sulfur dioxide results in acid rain when it reacts with water in the air, which can damage vegetation, soil and kill wildlife. 

• Cold carbon dioxide is heavier than air, so it can become concentrated in low-lying volcanic areas such as river valleys. 

• Large amounts of carbon dioxide in the air can kill wildlife, and in the soil, can destroy vegetation. 

volcanic gases : destroys properties and infrastructure

Sulfur dioxide results in acid rain, which can corrode buildings and infrastructure.

volcanic gases : threatens public health and cause injuries and fatalities

• Sulfur dioxide imitates skin, eyes, nose and throat. 

• Air containing over 3% carbon dioxide can cause headaches and breathing difficulties, and when it exceeds 15%, may cause death. 

volcanic gases : example

Dieng volcano eruption in Indonesia in 1979 which released deadly amounts of CO2 and killed about 150 ppl. 

lava flows : destroys ecosystems

Hot, low-silica lava can travel over some distances, destroying forests, other habitats and ecosystems in them.

lava flows : destroy properties and infrastructure

Lava can burn through homes, properties and infrastructure

lava flows : disrupts services

Lava can destroy electricity and communication cables, and water and gas pipes, disrupting supply of these services.

lava flows : example

In 2018 Kilauea eruption in Hawaii : far reaching lava flows destroyed more than 600 homes and huge areas of forests and ecosystems. Telephone and power lines were damaged, causing widespread communication outages. 

pyroclastic flow

hot cloud of gas, ash and rocks travelling down the slopes of a volcano at great speeds

pyroclastic flow : destroys ecosystems

• Huge areas of forests may be destroyed, resulting in biodiversity loss. 

• Thick layers of ash cover the path of the flows, polluting huge areas of forests.

pyroclastic flow : destroys properties and infrastructure

The hot flows can burn through all homes, properties and infrastructure in their path.

pyroclastic flow : disrupts services

The hot flows can destroy electricity and communication cables, and gas pipes, disrupting supply of these services

pyroclastic flows : threatens public health and causes injuries and fatalities

extreme temperatures can burn, and kill people in a fraction of a second

pyroclastic flows : example

2010 Mount Merapi eruption in Indonesia : blasted a series of pyroclastic flows down the slopes of the volcano which were inhabited by many villagers. About 350 people were killed, mostly due to burns and blast injuries. Huge areas of forest were burnt.

lahars

mudflows compromising water and volcanic ash, formed when huge amounts of ash and rocks ejected during eruption mix with water

lahars : destroys ecosystems

• Lahars can cover forests and other ecosystems with thick mud which hardens like concrete, destroying them. 

• Lahars can pollute rivers, killing aquatic life

lahars : destroy properties and infrastructure

• Lahar can bury houses and buildings, destroying them. 

•  Lahars can cover farms with thick mud, which hardens like concrete, damaging them.

lahars : disrupts services

• Roads and railways can be blocked by debris, making it difficult to rescue people or supply emergency aid. 

• Lahars can damage communication cables, and water and gas pipes, disrupting supply of these services.

lahars : threatens health and causes injuries and fatalities

Lahars can bury houses and its residents, resulting in loss of lives

lahars : example

In 1985 Nevado Del Ruiz eruption in Colombia : huge amounts of volcanic ash and rocks released which melted snow and ice, meltwater formed lahars and fast moving lahars buried more than 20k people in the nearby town of Armero within seconds. Rivers were highly muddied by the lahars, killing many fish.

volcanic landslides : destroys ecosystems

• Fast moving debris can bury huge areas of forest and wetlands

• Debris from landslides of the polluted rivers, killing aquatic  life

• Debris blocked rivers, causing floss that can damage nearby ecosystems and properties

volcanic landslides : destroys properties and infrastructure

Debris buries villages and farms, destroying properties and infrastructure

volcanic landslides : disrupts services

• Debris can snap electricity and communication cables, and water and gas pipes, disrupting supply of these services

• Debris blocks roads and railways, making it difficult to rescue people or supply emergency aid

volcanic landslides : causes injuries and fatalities

• Debris can bury people or hit them, causing injuries and loss of lives.

• Debris blocks rivers, resulting in floods, which can drown people.

volcanic landslides : example

In 1980 Mt St Helens eruption in USA : north face of the volcanic cone collapsed which caused volcanic landslides that traveled as far as 23km from the volcano and destroyed huge areas of land and killed many wildlife

benefits of volcanic eruptions and living near volcanoes

1. farming with fertile soil

2. extracting precious minerals and fossil fuels

3. harnessing geothermal energy

4. tourism activities

benefits : farming with fertile soil

• Over thousands of years, volcanic rocks break down and undergo weathering to form fertile soils.

• They are suitable for agriculture as they can produce higher crop yields.

• Locals benefit from growing a variety of crops or earning more from higher crop yields.

• Example: The best rice-growing regions in Indonesia are near volcanoes, such as in Bali, which has several volcanoes such as Mount Agung. Despite their continuous use, soils in Bali are more fertile than most non-volcanic areas of Indonesia.

benefits : extracting precious minerals and fossil fuels

• Some magma may cool and solidify beneath volcanoes, forming precious minerals such as copper, silver and gold.

• Locals living near volcanoes can be employed to mine these minerals, which provides them with a source of income.

• Governments may sell these precious minerals to generate revenue, which can in turn be used to provide social services to locals such as education and healthcare.

• Volcanic materials, such as ash and sand, may also be mined and used as construction materials.

• Example: Thousands of locals living on Mount Merapi are employed to mine volcanic sand as it is suitable for constructing buildings 

benefits : harnessing geothermal energy

• geothermal energy is derived from heat in earth’s crust

• can be harnessed in tectonically active areas

• beneath earth’s surface, hot rocks heat up groundwater

• stream that is formed is harnessed to generate electricity

• locals benefit from cheaper electricity produced locally

• locals can be employed to work in geothermal plants

• examples : Most of Iceland’s electricity is generated from geothermal power because of the large number of volcanoes in the country. In northern California, the Geysers geothermal field produces enough electricity to meet the power demands of San Francisco.

benefits : tourism activities

• different volcanic features like the crater appeal to tourists

• tourists can engage in various activities, such as hiking and sightseeing

• tourism provides locals with employment opportunities such as tour guides, providing tourist accommodation and selling food and souvenirs

• tourism thus boosts local economic development

• example : The Hawaiian islands are popular tourist locations for its scenic volcanic landscapes. Tourism generates an annual income of about US$88 million and provides locals with thousands of jobs