Tectonics

Compare challenges at a convergent boundary (Japan) and divergent boundary (Iceland).

• Destructive earthquakes (up to 9.5 magnitude) due to Pacific Plate subducting under Eurasian Plate.

• Volcanic eruptions (e.g., Mt. Fuji) from magma rising at subduction zones; steep-sided stratovolcanoes.

• Tsunamis triggered by seismic activity (e.g., 2011 Tōhoku tsunami).

• Divergent (Iceland):

  • Frequent but smaller earthquakes (5.0–6.0 magnitude) along the Mid-Atlantic Ridge.

  • Gentle volcanic eruptions (e.g., Eyjafjallajökull 2010) with basaltic lava flows.

  • Less immediate danger but ongoing geothermal activity disrupts infrastructure.

Why do collision zones (Himalayas) lack volcanoes?

Continental plates (Eurasian and Indian) have similar density, causing uplift (mountains) instead of subduction. No magma generation, but massive earthquakes (e.g., 2015 Nepal, magnitude 7.8).

Explain two challenges LICs face in managing volcanic hazards (e.g., DRC’s Mt. Nyiragongo).

1. Economic: Poverty limits rebuilding/insurance (e.g., 400,000 evacuated in 2021; homes destroyed by lava).

2. Governance: Poor communication/corruption delays aid (e.g., refugees overcrowded in camps).

Assess challenges for HICs (Japan’s Mt. Sakurajima).

• 
  Economic: High costs of protecting 650,000 residents and tourism infrastructure (e.g., ash cleanup, insurance).

• Social: Long-term disruption to farmland/industries despite government aid (e.g., 2016 Kumamoto earthquakes).

Who faces harder impacts: HICs or LICs? Justify using SEE factors.

Social Impact: LICs face harder social impacts from tectonic hazards due to weaker infrastructure, limited medical care, and higher casualties. HICs have better emergency response and healthcare, reducing deaths and injuries.

Economic Impact: LICs suffer greater economic losses as rebuilding is costly and resources are scarce. HICs face higher financial damages, but they recover faster due to insurance and stronger economies.

Environmental Impact: Both HICs and LICs experience environmental damage, such as landslides and destroyed ecosystems. However, LICs struggle more with long-term recovery due to fewer resources for rebuilding and protection.

Define subduction zone and tsunami with examples.

• Subduction Zone: Oceanic plate sinks under continental plate (e.g., Japan Trench).

• Tsunami: Destructive wave from tectonic uplift (e.g., 2004 Indian Ocean tsunami).

Contrast primary and secondary impacts of earthquakes.

• Primary: Immediate damage (e.g., collapsed buildings in Haiti 2010).

• Secondary: Follow-on effects (e.g., Japan’s 2011 nuclear meltdowns at Fukushima).

How does silica content affect volcanic hazards?

• Basic Lava (Pāhoehoe): Low silica → low viscosity → flows far (e.g., Hawaii’s shield volcanoes).

• Acid Lava (‘A‘ā): High silica → high viscosity → explosive eruptions (e.g., Mt. St. Helens).

Compare 2011 Japan (HIC) and 2010 Haiti (LIC) earthquakes.

• Japan:

  • Primary: 15,900 deaths, $235B damage.

  • Secondary: Nuclear meltdowns, 350,000 homeless.

• Haiti:

  • Primary: 316,000 deaths, 1 million homeless.

  • Secondary: Cholera outbreak (8,000+ deaths), port destruction delaying aid.

Why are LICs less able to respond to earthquakes?

• Economic: No earthquake-proof infrastructure (e.g., Haiti’s poorly built homes).

• Governance: Weak emergency services (e.g., Haiti’s reliance on foreign aid).

Assess: “HICs respond better to disasters.”

• True: Japan’s drills, tsunami walls, and tech (e.g., earthquake dampers).

• False: HICs still face systemic failures (e.g., Fukushima meltdown due to outdated nuclear plants).