Geography

Tectonics Cluster

Topic 2 | Earthquakes and Volcanoes

2.4 Impacts of Tectonic Hazards on Natural and Human Systems

Hazards Associated with Volcanic Eruptions

  • Tephra

  • Volcanic Gases

  • Lava Flows

  • Pyroclastic Flows

  • Lahars

  • Volcanic Landslides

How Does Tephra Affect Natural and Human Systems?

Tephra General

  • Definition: General term for airborne fragments of ejected volcanic material.

Impact on Natural Systems

  • Destroys ecosystems.

Impact on Human Systems

  • Destroys properties and infrastructure.

  • Disrupts services.

  • Causes injuries and fatalities.

Explanation

  • Ash can be carried thousands of kilometers by prevailing winds, polluting large areas of forests, rivers, and other habitats, thus destroying ecosystems.

  • Ash can suffocate and kill wildlife, also causing blindness in birds by gluing their eyelids together due to ash accumulation.

  • Volcanic bombs: Range from a few centimeters to the size of vehicles and can hit properties, causing damage.

  • Ashfall can accumulate on roofs; when saturated with water, the weight can double, leading to roof collapses.

  • Ash's corrosive nature weakens building structures, increasing their likelihood of collapse.

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

  • Ash particles can damage aircraft engines, leading to airspace closures and disrupted air transportation services.

  • Volcanic bombs pose a direct threat to people by causing injuries and fatalities.

  • Ashfall can result in respiratory issues, eye irritation, and suffocation.

Example

  • 1991 Mount Pinatubo Eruption, Philippines

    • Emitted large amounts of ash burying over 180 km² of forests under approximately 25 cm of ash.

    • Destroyed 800 km² of rice fields, severely impacting farmers' livelihoods.

    • Led to closure of seven airports and cancellation of numerous flights, causing transport disruption.

    • Damage to some airplanes was also reported.

How Do Volcanic Gases Affect Natural and Human Systems?

Volcanic Gases

  • Common Gases: Sulfur dioxide and carbon dioxide released in large quantities during eruptions.

Impact on Natural Systems

  • Destroys ecosystems.

Impact on Human Systems

  • Destroys properties and infrastructure.

  • Threatens public health, causing injuries and fatalities.

Explanation

  • Sulfur Dioxide: Reacts with moisture in the air to produce acid rain, which can damage vegetation and soil and kill wildlife.

  • Carbon Dioxide: Being heavier than air, it can accumulate in low-lying areas, leading to wildlife death and vegetation destruction.

    • Air with over 3% carbon dioxide cause headaches and breathing difficulties, while concentrations over 15% can be fatal.

Example

  • Dieng Volcano Eruption, Indonesia, 1979

    • Released lethal amounts of carbon dioxide, resulting in approximately 150 fatalities.

How Do Lava Flows Affect Natural and Human Systems?

Lava Flows

  • Extremely hot, can travel over long distances within the volcano's geographic area.

Impact on Natural Systems

  • Destroys ecosystems.

Impact on Human Systems

  • Destroys properties and infrastructure.

  • Disrupts services.

Explanation

  • Hot, low-silica lava destroys forests and other habitats.

  • Lava can incinerate homes and properties.

  • Disruption of electricity, communication cables, and water and gas pipes can occur, impacting supply.

Example

  • 2018 Kilauea Eruption, Hawaii

    • Lava flows obliterated over 600 homes and devastated significant forest areas.

    • Damage to telephone and power lines caused widespread outages.

How Do Pyroclastic Flows Affect Natural and Human Systems?

Pyroclastic Flows

  • Defined as hot clouds of gas, ash, and rocks, travelling down volcanic slopes at speeds exceeding 200 km/h.

Impact on Natural Systems

  • Destroys ecosystems.

Impact on Human Systems

  • Destroys properties and infrastructure.

  • Disrupts services.

  • Threatens public health, causing injuries and fatalities.

Explanation

  • Large forested areas can be devastated, resulting in loss of biodiversity.

  • Ash layers from pyroclastic flows can pollute significant areas of forest.

  • The high temperatures of flows can incinerate everything in their paths, including homes and infrastructure.

  • Service disruptions due to destruction of cables and gas pipes.

Example

  • 2010 Mount Merapi Eruption, Indonesia

    • Generated pyroclastic flows that damaged villages, causing around 350 deaths, mostly from burns and blast injuries.

    • Extensively burnt huge forest areas.

How Do Lahars Affect Natural and Human Systems?

Lahars

  • Defined as mudflows composed of water and volcanic ash, formed when ash and rocks ejected during eruptions mix with water.

  • Can be triggered when pyroclastic flows melt snow/ice or intense rainfall washes down ash.

Impact on Natural Systems

  • Destroys ecosystems.

Impact on Human Systems

  • Destroys properties and infrastructure.

  • Disrupts services.

  • Threatens public health, causing injuries and fatalities.

Explanation

  • Lahars can cover forests and ecosystems with concrete-like mud, destroying them.

  • Can pollute rivers leading to aquatic life loss.

  • Lahars can bury buildings and farms, damaging them.

  • Disrupt local transport routes, hampering emergency aid delivery.

Example

  • 1985 Nevado Del Ruiz Eruption, Colombia

    • Released vast amounts of ash and volcanic rocks that melted snow and ice.

    • Resulting lahars buried over 20,000 people in Armero swiftly and muddied river systems, killing fish populations.

How Do Volcanic Landslides Affect Natural and Human Systems?

Volcanic Landslides

  • Common on high, steep volcanic cones made of solidified lava and tephra.

  • Triggered by explosive eruptions causing loose volcanic material to move downward.

Impact on Natural Systems

  • Destroys ecosystems.

Impact on Human Systems

  • Destroys properties and infrastructure.

  • Disrupts services.

  • Causes injuries and fatalities.

Explanation

  • Fast-moving debris can bury vast forested areas and wetlands.

  • Landslide rubble can pollute rivers, leading to aquatic life destruction, and block rivers, inducing flooding.

  • Landslides destroy properties and infrastructure, blocking roads and transport routes for rescue and aid.

Example

  • 1980 Mt St Helens Eruption, USA

    • Resulted in the north face of the volcanic cone collapsing.

    • This caused landslides traveling up to 23 km away, destroying large areas of land and wildlife.

Benefits of Volcanic Eruptions and Living Near Volcanoes

Benefits of Living Near Volcanoes

  1. Farming with Fertile Soil

    • Volcanic rocks weather over time, creating fertile soils suitable for agriculture leading to higher crop yields.

    • Example: In Indonesia, volcanic regions like Bali are ideal for rice farming.

  2. Extracting Precious Minerals and Fossil Fuels

    • Magma solidification beneath volcanoes creates precious minerals (copper, silver, gold) enabling local mining jobs and income generation.

    • Example: Locals on Mount Merapi mine volcanic sand used for construction.

  3. Harnessing Geothermal Energy

    • Geothermal energy is sourced from Earth’s heat, particularly in tectonically active regions, producing cheaper electricity.

    • Example: Iceland derives most electricity from geothermal sources due to its volcanic activity; Northern California’s Geysers field meets electricity needs for San Francisco.

  4. Tourism Activities

    • Volcanic landscapes attract tourism for hiking and sightseeing, generating local jobs and income.

    • Example: The Hawaiian Islands’ volcanic beauty generates around USD 88 million annually and creates numerous jobs.

Disaster Risk Management

3.1 Achieving Sustainable Development through Disaster Risk Management

What is Tectonic Disaster Risk?

  • Definition: Potential property damage, injury, and loss of lives associated with tectonic hazards over a timeframe.

  • Determined by: the interaction between the hazard, vulnerability, and exposure conditions.

What is Disaster Risk Management?

  • Involves plans and actions to:

    • Prevent risk before occurrences of tectonic hazards.

    • Reduce disaster risks while hazards are occurring.

    • Manage risks post-occurrence of hazards.

  • Strategies:

    • Designing hazard-resistant buildings (like Taipei 101) to withstand earthquakes.

    • Early monitoring systems for tsunamis/earthquakes for timely evacuations.

    • Insurance coverage for financial recovery post-disaster.

    • Strengthens community resilience against tectonic hazards.

How Do Disaster Risks and Losses Hinder Development?

Consequences of Disaster Risks

Environmental Consequences

  • Landslides from volcanic eruptions can bury vast areas, causing ecosystem destruction and biodiversity loss.

  • The debris from landslides pollutes, killing aquatic life and blocking rivers, resulting in flooding.

Social Consequences

  • Tsunamis and other hazards lead to injuries, loss of life, and distress in afflicted communities.

Economic Consequences

  • Destruction of homes leads to homelessness and impoverishment due to loss of income sources and properties.

  • Governments incur restoration costs, redirecting funds from development to recovery efforts.

Development Impacts

  • Hindered recovery post-disaster affects developmental investments and contributes to poverty.

    • Example: The 2004 Indian Ocean tsunami increased poverty levels in Aceh, Indonesia, drastically.

Importance of Reducing Disaster Risks

  • Effective in mitigating consequences for developing countries, which often lack resources to manage risks adequately.

  • Example: Haiti's 2010 earthquake caused significant devastation due to inadequate infrastructure compared to Japan's 2011 tsunami.

  • Investment in disaster risk reduction is cost-effective, preventing future losses and contributing to overall sustainable development.

    • Example: The 2010 Chile earthquake had lower losses due to earthquake-resistant infrastructure compared to the Haiti event.