Earthquakes + Volcanoes

• What is formed when magma erupts onto the Earth's surface?

  A volcano
• How is the magnitude of a volcanic eruption measured?

  On the Volcanic Explosivity Index (VEI)
• What was the highest recorded VEI in human history?

  8 (Tambora 1815)
• What are the main types of volcanoes and their characteristics?

  • Composite (strato-volcanoes):
  • Steep-sided
  • Sticky (viscous) lava
  • More explosive eruptions
  • Formed from alternating layers of ash and lava
  • Tend to form on convergent (destructive) plate boundaries

  
  

  • Shield volcanoes:
  • Gently sloping sides
  • Runny/thin lava
  • Less explosive - gentle eruptions
  • Tend to form on divergent (constructive) plate boundaries or hot spots

  
• What are the three classifications of volcanoes based on activity?

  Active, dormant, extinct
• What defines an active volcano?

  A volcano that has recently erupted and is likely to erupt again
• What is a dormant volcano?

  A volcano that has not erupted for many years but has evidence of a magma reservoir
• What characterizes an extinct volcano?

  A volcano that shows no evidence of eruption in historic times and has no magma reservoir
• What are the features of volcanic eruptions?

  • Lava: Magma that erupts to the surface; can be thin/runny or thick/slow.
  • Ash: Pulverized solid lava < 2mm in diameter; can travel thousands of kilometers.
  • Pyroclastic flow: Fast-moving, hot clouds of gases mixed with ash; speeds up to 700 km/h.
  • Lahars: Fast-moving mudflows created when snow and ice melt during eruptions.
  • Volcanic bombs: Fragments of molten rock ejected from the volcano, ranging from 60mm to 5m.
• How do earthquakes relate to volcanic activity?

  Magma rising through vents increases pressure on the Earth's crust, leading to tremors
• What is the definition of an earthquake?

  The sudden, violent shaking of the ground
• What causes earthquakes?

  Pressure building when tectonic plates move
• What is the epicenter of an earthquake?

  The point on the Earth's surface directly above the focus
• What is the focus of an earthquake?

  The point at which the earthquake starts below the Earth's surface
• How is the magnitude of an earthquake measured?

  On the Moment Magnitude Scale
• What does the Mercalli Scale measure?

  The damage caused by earthquakes
• Where do most earthquakes occur?

  At or near plate boundaries
• What are the types of plate boundaries where earthquakes occur?

  • Constructive (divergent)
  • Destructive (convergent)
  • Collision
  • Conservative (transform)
• How do earthquakes differ at constructive plate boundaries compared to destructive ones?

  Earthquakes at constructive boundaries tend to be weaker
• What happens at a convergent plate boundary?

  The denser oceanic plate subducts under the lighter continental plate
• What is the sequence of events during an earthquake?

  Tectonic plates get stuck, pressure builds, and then they jolt free releasing energy
• What human activities can cause earthquakes?

  Drilling into the crust or mining
• What percentage of earthquakes occur along the Pacific 'Ring of Fire'?

  Approximately 90%
• Where do most volcanoes occur?

  At divergent (constructive) and convergent (destructive) plate boundaries
• What is a hotspot in relation to volcanoes?

  A plume of magma that escapes through the Earth's crust away from plate boundaries
• What are the four main layers of the Earth?

  • Inner core: Solid and dense, composed of iron and nickel, ~1400 km in diameter, ~5500°C
  • Outer core: Semi-molten metal layer, ~2100 km thick, ~5000−5500°C
  • Mantle: Semi-molten layer, ~2900 km thick
  • Crust: Varies in thickness, made up of continental and oceanic crust

  
• What are the two types of crust?

  Continental crust and oceanic crust
• How does oceanic crust differ from continental crust?

  Oceanic crust is thinner, denser, and continually created and destroyed
• What are the types of plate boundaries?

  • Divergent (constructive)
  • Convergent (destructive)
  • Collision
  • Transform (conservative)
• What occurs at a divergent plate boundary?

  The plates are moving apart, allowing lava to escape and form new crust
• What happens at a convergent plate boundary?

  The heavier oceanic plate subducts under the lighter continental plate
• What is formed at a collision boundary?

  Fold mountains, as the land is pushed upwards

  
• What is the only hazard at a transform (conservative) boundary?

  Earthquakes
• What are the primary and secondary hazards of earthquakes and volcanic eruptions?

  Primary hazards:

  • Ground shaking
  • Surface rupture
  • Liquefaction
  • Landslides
  • Tsunami
  • Fires

  
  

  Secondary hazards:

  • Pyroclastic flow
  • Lava flow
  • Volcanic bombs
  • Lahars (mudflow)
  • Direct ash fall
  • Acid rain
  • Ash fallout from the atmosphere
• What factors affect the impacts of earthquakes and volcanic eruptions?

  Human factors:

  • Building construction and design
  • Building density
  • Population density
  • Preparation (e.g., earthquake drills)

  
  

  Physical factors:

  • Magnitude of the earthquake
  • Geology of the area
  • Distance from the epicenter
  • Depth of the earthquake
• What is the impact of poorly constructed buildings during an earthquake?

  They are more likely to collapse
• How does population density affect earthquake impacts?

  A higher population density increases the likelihood of injuries or fatalities
• How does distance from the epicenter affect earthquake impacts?

  The closer to the epicenter, the stronger the shock waves experienced
• What is the effect of depth on earthquake impacts?

  Shallower earthquakes mean less energy is absorbed before reaching the surface
• What are the effects of volcanic eruptions on the environment?

  • Pyroclastic flows can destroy everything in their path.
  • Lava flows can cover large areas and destroy habitats.
  • Ash fall can affect air quality and agriculture.
  • Lahars can cause flooding and destruction.
  • Volcanic gases can contribute to climate change.