Hazardous Earth - Tectonics Notes

Crust: Continental (granitic, thicker, older, less dense) and Oceanic (basaltic, thinner, younger, more dense).
Mantle: Upper (solid, silica-based), Lower (liquid).
Core: Outer (liquid, iron/nickel), Inner (solid).

Divergent: Plates move apart, magma rises, forming new land or shield volcanoes (e.g., Mid-Atlantic Ridge). Earthquakes can occur.
Conservative: Plates slide past each other, no crust created/destroyed. Earthquakes occur (e.g., San Andreas Fault).
Convergent: Plates collide. Oceanic plate subducts under continental, creating trenches and composite volcanoes. Earthquakes occur. Collision of two equal density plates forms fold mountains.

Residual heat and radioactive decay in the core generate heat.
Convection currents in the mantle cause plates to collide, slide, or be pulled apart.

Volcanoes: Mainly along plate margins. Measured using the Volcanic Explosivity Index (VEI).
Earthquakes: Occur on conservative plate margins. Focus (below surface), Epicentre (above surface).
Tsunamis: Oceanic waves caused by undersea earthquakes/volcanic eruptions.

Shield (Divergent): Low, flat, gentle slopes. Basaltic magma, fluid, frequent gentle eruptions (e.g., Mauna Loa).
Composite (Convergent): Steep sided, layers of ash and lava. Granitic/andesitic magma, viscous, infrequent explosive eruptions (e.g. Montserrat).
Hotspots (Divergent): Low, flat, gentle slopes. Basaltic magma, fluid, frequent gentle eruptions (e.g., Kilauea, Hawaii).

Volcanic Eruption (Emerging Country): Mount Pinatubo, Philippines, 1991
- Primary impacts: Deaths, homes destroyed, power cuts.
- Secondary impacts: Disease, crop destruction, economic devastation.
- Responses: Prediction, warnings, evacuation, long-term dykes and dams.
Earthquake (Developed Country): Tohoku, Japan, 2011 (9.0 Richter scale)
- Primary Impacts: Deaths, building destruction, infrastructure collapse
- Secondary Impacts: Tsunami, nuclear meltdown, homelessness, cost of rebuilding = £300 billion.
- Responses: Tsunami warning, rescue efforts, evacuation.
Earthquake (Developing Country): Port-au-Prince, Haiti, 2010 (7.0 Richter scale)
- Primary impacts: Shanty towns crumbled, business collapse, damaged infrastructure.
- Secondary impacts: Long-term displacement, job loss, transport disruption, disease.
- Responses: Rescue teams, international aid, debt relief.
Volcanic Eruption (Developed Country): Hawaii, USA (Kilauea since 1983)
- Primary impacts: Land destroyed, homes destroyed, utilities damaged.
- Secondary impacts: Air pollution, acid rain, respiratory disease, increased tourism.