Volcanic hazards Flashcards
Describe features of lava at constructive plate margins ?
- Basaltic lava: hot with low viscosity lava that flows quickly
- Frequent and long lasting eruptions
- Non violent eruptions
- Submarine volcanoes with margins underwater form ocean ridges
- Volcanoes with margins on land form rift valleys
Where do volcanoes that occur away from plate margins occur at
Hot spots above magma plumes with basaltic lava that forms shield volcanoes
Describe features of lava at destructive plate margins
- Andesitic and rhyolitic lava which is cooler and more viscous (more silicon) than basaltic so flows less easy
- Infrequent eruptions which last short amounts of time
- Explosive volcanic activity: due to involvement of steam from water trapped during subduction forming viscous lava blockages in vents causing pressure to build in PHREATIC ZONE
Explain pyroclastic flow as primary hazards
- Mixture of super-heated gas and volcanic rock that flows down sides of volcanoes
- Travels at high speed and aided by force of gravity
- Can causes widespread death and destruction
What are nuee ardente another name for ?
Pyroclastic flow
Explain lava flows as primary hazards
- Lava moving down side of volcano from a vent
- Speed and distanced traveled depend on temperature, viscosity, steepness of slope
- Slow but destructive of anything in path
Explain volcanic gases as a primary hazard
- Lava contains gases such as CO2 and sulfur dioxide which is released during eruptions
- Gases can cause harm and breathing difficulties to humans and animals
Explain pyroclastic and ash fallout as a primary hazard
- Material ejected from volcano during eruption and falls back to ground
- Ashfallout: when fallout consists of mainly ash
- Material can travel 1000s km away from volcano and ranges in sizes so heavier particles are deposited earlier
- Large pieces can damage infrastructure or kill people
- Finer pieces can kill vegetation, stop transport services and cause breathing difficulties
What is another name for pyroclastic material?
Tephra
Explain mudflows as secondary hazards
- When volcanic material mixes with water from rainfall or melted ice
- Flow moves quickly and is aided by gravity
- Can bury or destroy natural habitats, settlements and infrastructure
What is another name for a mudflow ?
Lahars
Explain acid rain as a secondary hazard
Volcanic gases react with water vapour in atmosphere which falls as acid rain which can damage ecosystems and cause stone to disintegrate which damages infrastructure
Explain the spatial distribution of volcanic hazards
Most occur near constructive and destructive plate margins or on hot spots above magma plumes.Most located in the ring of fire in the Pacific ocean
Explain the variation in magnitude of volcanic eruptions
Measured by the VEI (volcanic explosivity Index) which grades from 0-8 based on amount of material ejected and the height the material is ejected
Explain the frequency of volcanic eruptions
Less frequent- more explosive and damaging
More frequent- less explosive and damaging
Depends on volcano type
Explain the regularity of volcanic eruptions
Some erupt in regular intervals whereas other are dormant for long periods of time then erupt several times in quick succession
Explain the predictabiity of volcanic hazards
- Regularity of eruptions can be an indicator of next eruptions
- Monitor earthquakes
- Monitor changes in shape and composition of volcanic gases leaving vents of volcano
Give a prevention strategy as a long term response to volcanic hazards
- Prevent land use being a risk by preventing land around volcanoes being developed on
Give 2 preparedness strategies as long term responses to volcanic hazards
- Communities establish search and rescue teams to take impacts of eruptions
- Authorities install earthquake monitoring systems to predict eruptions and inform local people
Give 2 adaptation strategies as long term responses to volcanic hazards
- Strengthen buildings to reduce chance of collapse with layers of ash falling
- People capitalise on living near a volcano e.g. farming on fertile lands or working in tourism
How is climate change influencing volcanic hazards ?
- Deglaciation results in a loss of weight on Earths surface causes DECOMPRESSION MELTING where a lower pressure facilitates melting in the mantle forming liquid magma which fuels volcanic activity in places such as Iceland
