Volcanic hazards Flashcards
Explain why some volcanic eruptions are more violent than others
At composite volcanos the lave is more viscous
So it is harder for the gas to escape
This results in more explosive eruptions
Eruptions at destructive margins
Tend to be High magnitude, explosive, infrequent Irregular, difficlut to predict
Eruptions at constructive margins
Tend to be Low magnitude, gentle, frequent, more regular, easier to predict
Type of lava at destructive margins
- Andesitic and Rhyolitic lava
- high viscosity (Thicker) - Moves slower
Type of lava at constructive margins and hotspots
- Balsaltic lava
- Low viscosity (Less thick) - Moves faster
What gases get released from volcanos and what do they cause?
- Carbon dioxide CO2 - Contibutes to the greenhouse effect and can affect animals and people living around the volcano
- Sulphur dioxide SO2 - Can form acid rain H2SO4
Pyroclastic fallout
It is any material that has been ejected from a volcano and has travelled through the air or atmosphere and fallen to earth and can block out the sun
Ash fallout
Ash is tiny pieces of burnt rock fragment that are blown into the atmosphere and can block out the sun
Pyroclastic flows/Nuées ardentes
They are currents of hot ash, lava and gas that can move downhill at speeds of up to 500km/h during an eruption.
Pyroclastic flows are impossible to outrun.
They can reach temperatures of up to 1000°C and can cover distances of up to 30km from the volcano
Lahars (Mudflows)
- Occurs if volcanic ash or lava mixes with water and are fast moving and destroy buildings and vegetation in its path
- Can happen if the erupting volcano has a glacier on top, or snow, ice or water on its slopes or nearby.
Tephra
- Rock fragments that are ejected at high speeds and can travel as far as 80km away
- Can be small or large
