Natural Hazards and Earth's Interior Structure

Natural Hazards

• Natural hazards are natural events threatening people, potentially causing damage, destruction, and death; they must involve people. Examples include earthquakes, volcanic eruptions, tropical storms, and floods.
• Three main types of natural hazards:
  • Atmospheric hazards: Caused by weather and atmospheric processes.
  • Geological/Tectonic hazards: Caused by Earth and tectonic plate movements.
  • Hydrological hazards: Caused by water movement and distribution.

Earth's Interior Structure

• The Earth has four layers: Crust, Mantle, Outer Core, and Inner Core.
• Crust: Solid, composed of magnesium, sulfur, and other elements; up to 80 km deep.
• Mantle: 80 km below surface, solid and liquid, composed of oxygen, magnesium, aluminum, iron, and magma.
• Outer Core: 4,828 km below surface, primarily liquid, composed mostly of molten iron and nickel.
• Inner Core: 6,437 km below surface, solid due to immense pressure, composed of nickel and iron; hotter than the surface of the sun.

Evidence of Continental Drift

• Continents fit together like a jigsaw puzzle.
• Similar rock formations exist on separated continents (e.g., Africa and South America).
• Matching fossils are found on different continents.
• Seafloor spreading supports continental drift.

Convection Currents

• Convection currents are fluid movements due to temperature and density differences.
• Mantle convection works like a conveyor belt in three steps:
  1. Heated magma in the lower mantle becomes less dense and rises.
  2. Rising magma cools, becomes denser, and sinks back down.
  3. This cycle creates continuous flow.
• Convection currents drive plate movement.

Plate Boundaries

• Three main types of plate boundaries:
  • Constructive: Plates move apart, creating volcanoes and new land; earthquakes occur. (e.g., Mid-Atlantic Ridge)
  • Destructive (Subduction): Oceanic plate subducts under a continental plate (denser oceanic plate sinks), causing volcanoes, earthquakes, and sometimes tsunamis. (e.g., Eurasian and Pacific plates near Japan)
  • Collision: Two plates of the same type (oceanic or continental) collide, forming mountains (or oceanic mountains, island chains); friction and stress can cause earthquakes. (e.g., Himalayas)
  • Conservative: Plates slide past each other; stress buildup leads to earthquakes. (e.g., San Andreas Fault)

Iceland 2010 Eruption (Case Study)

• Iceland lies between the Eurasian and North American plates, experiencing constructive plate activity (plates moving apart).
• A stratovolcano eruption with an ice cap caused a significant ash cloud, significantly impacting Europe.
• An initial VEI (Volcanic Explosivity Index) 3 eruption had extended eruptions and winds that took the ash cloud across Europe.
• Major Impacts:
  • Flight cancellations, economic disruption ($5 Billion global cost).
  • Crop damage, flower export disruption to Europe.
  • Increased ocean biological productivity.
  • Positive impacts: prevented millions of tons of CO2 emission.
• Immediate Responses:
  • EU air traffic plans and travel ban.
  • Improved ash cloud monitoring.
• Long-term Responses:
  • Red Cross aid to victims.

Volcanoes

• Stratovolcano (Composite Volcano): Very viscous lava flows, alternating layers of lava and pyroclastic material, steep slopes, often located on constructive margins, potentially dangerous due to long dormant periods, example: Mt. St. Helens.
• Shield Volcano: Little pyroclastic material; long thin lava flows built up over a vent; gentle slopes.
• Volcanic dangers: ash, gas, post-eruption famine and disease.
• Volcanic benefits: fertile soil, tourism, geothermal energy.

Haiti Earthquake, 2010 (Case Study)

• Conservative fault activity between the Caribbean and North American plates caused a 7.3 magnitude earthquake.
• Major Impacts:
  • Economic damage ($14 Billion),
  • Extensive property destruction—300,000 homes destroyed, 4,000 schools, Presidential Palace damage.
  • Loss of life—316,000 deaths, widespread cholera, government worker losses.
  • Infrastructure damage.
• Immediate Responses:
  • International rescue teams.
  • Debt relief (World Bank).
  • Donations for humanitarian aid.
• Long-term Responses:
  • Ongoing recovery efforts, displacement camps.

This quiz covers the essential aspects of natural hazards and the Earth's interior structure. Explore the types of natural hazards, including atmospheric, geological, and hydrological, as well as the four layers of the Earth: crust, mantle, outer core, and inner core. Test your knowledge on these fundamental geological concepts.