Understanding Volcanoes and Tectonic Plates

Key Concepts of Volcanoes and Plate Tectonics

Earth's Structure
- Crust: Two types - Continental (70-40 km deep, $2.7$ g/cm $^3$ density) and Oceanic (6 km deep, $3$ g/cm $^3$ density).
- The Earth's crust is broken into tectonic plates.
Types of Natural Hazards
- Geomorphological: e.g., flooding.
- Biological: e.g., forest fires.
- Atmospheric: e.g., hurricanes, tornadoes.
- Tectonic: e.g., earthquakes, volcanoes.
Tectonic Plates and Their Movement
- Plates are moved by convection currents in the mantle.
- Slab pull and ridge push are the primary mechanisms for plate movement.
- Types of plate margins:
- Constructive: Plates move apart (e.g., mid-ocean ridges).
- Conservative: Plates slide past each other.
- Destructive: Plates move towards each other (subduction zones).
Volcano Formation
- Destructive boundaries: Friction melts the plate forming magma.
- Constructive boundaries: Magma rises through gaps created by separating plates.
- Hotspots: Volcanoes that form away from plate boundaries (e.g., Mauna Loa).
Effects of Volcanic Eruptions
- Pyroclastic flows: Fast-moving currents that can be fatal.
- Lava flows: Can cause destruction but rarely produce fatalities.
- Ash: Blocks sunlight, affects climate, damages property.
- Mudflows: Caused by melting snow on volcanoes.
- Poisonous gases: Can be harmful to humans.
Lava Types and Volcanoes
- Different types of lava produce different types of volcanoes.
- Basic Lava
- Found near:
  - Ocean ridges (constructive plate boundaries)
  - Hot Spots
- Characteristics:
  - High temperature (c. $1000^\circ C$ )
  - Non-viscous (runny)
  - Thin
  - Fast flowing
- Ash production: Little ash is produced.
- Activity: No explosive activity.
- Acid Lava
- Found near:
  - Ocean trenches
  - Destructive plate boundaries
- Characteristics:
  - Lower temperature (c. $$700