Volcanic Hazards Flashcards
What are volcanoes? What is vulcanicity? - Volcanic Hazards
Volcanoes are landforms created over openings in the Earth’s crust by an accumulation of extrusive, eruptive products.
Vulcanicity is the collection of volcanic activities related to molten rock being forced into and out of crust.
Describe the type of volcano at constructive boundaries between 2 oceanic plates (type of lava, form of volcano, type and frequency of eruption) - Volcanic Hazards
Volcanoes at constructive boundaries between 2 oceanic plates are gently sloped, shallow volcanoes which are filled with basaltic lava. They create frequent but gentle eruptions which sees magma reach the surface as it spills up through a gap created by plate movement.
ICELAND - MID-ATLANTIC RIDGE
Describe the type of volcano at constructive plate boundaries between 2 continental plates (type of lava, form of volcano, type and frequency of eruption) Give an example of these volcanoes - Volcanic Hazards
Volcanoes at constructive boundaries between 2 continental plates are composite volcanoes with steeper sides, filled with andesitic lava. Creates infrequent but violent eruptions that may be explosive. Magma reaches the surface as crust thins out, forcing magma to the surface.
Example - KILIMANJARO
Describe the type of volcano at destructive plate margins (type of lava, form of volcano, type and frequency of eruption) Give an example of this type of volcano - Volcanic Hazards
Destructive margins produce composite volcanoes with steep sides and filled with andesitic lava. They produce infrequent and explosive eruptions, with magma reaching the surface as it is pressed upwards by the subduction of the oceanic plate.
Example - MARTINIQUE/MONTSERRAT
What causes hot spots? - Volcanic Hazards
Hot spots are caused when radioactive material beneath the Earth’s crust burns the lithosphere, allowing magma to seep through and create volcanoes.
What type of lava/volcano/eruptions exist at hot spot volcanoes? What examples of these volcanoes are there? - Volcanic Hazards
Lava - basaltic
Volcano - large, flat, shield volcanoes
Eruptions - frequent yet gentle
Seen on Hawaiian Islands in the Pacific
What is basaltic lava? What is andesitic lava? (Viscosity, eruption type, silica content) - Volcanic Hazards
Basaltic - causes gentle eruptions, less viscous, low silica content
Andesitic - causes violent eruptions, more viscous, higher silica content
What is the volcanic explosively index? - Volcanic Hazards
The volcanic explosively index is a scale which measures the severity and magnitude of an eruption on a scale of 0-8.
What is a fissure volcano? Describe its type of eruption, silica content, lava type, plate boundary - Volcanic Hazards
A fissure volcano is a volcano which produces very slow moving and gentle eruptions which are low in silica content (BASALTIC LAVA). This extrudes lava which is low in silica, usually from constructive plate boundaries or hotspots.
What is a shield volcano? Describe its type of eruption, silica content, lava type, plate boundary - Volcanic Hazards
A shield volcano is a flat, shallow volcano produced at constructive boundaries. This creates slow eruptions of basaltic lava which is low in silicates.
What is a composite volcano? Describe its type of eruption, silica content, lava type, plate boundary - Volcanic Hazards
A composite volcano is a volcano created by numerous layers of ash and lava. It produces violent, infrequent eruptions of andesitic lava at subduction plate boundaries.
What are primary hazards from volcanoes? What are secondary hazards? - Volcanic Hazards
Primary - lava flow, pyroclastic flow, tephra, nuées ardentes, ash fallout, volcanic gases
Secondary - mudflows/lahars, acid rain
What is a lava flow? What are their impacts? Where do these occur? - Volcanic Hazards
Lava flows are runny or viscous flows of lava depending on the temperature and composition of the lava. These are produced during volcanic eruptions and can travel at up to 40km/h, burning down structures or vegetation.
Occur at subduction zones, constructive margins and hot spots.
What are pyroclastic flows? What are their impacts? Where do they occur? - Volcanic Hazards
Pyroclastic flows are fast-moving flows of hot gas, rock and ash which can reach speeds of 700km/h. They travel downhill, causing instant death. Seen at Pompeii.
Occur at subductive margins with composite volcanoes.
What is tephra? What are their impacts? Where does it occur? - Volcanic Hazards
Tephra is rock material ejected by a volcano - anything from ash to large volcanic bombs. May destroy crops, can cause the closure of airspace.
Occurs at subduction margins.
What are nuées ardentes? What are their impacts? Where do they occur? - Volcanic Hazards
Nuées ardentes are dense, slower moving types of pyroclastic flow.
These occur at subduction zones.
What is ash fallout? What are its impacts? Where does this occur? - Volcanic Hazards
Ash fallout is thrown up into the atmosphere by large eruptions, small fragments of material. May be carried by winds over long distances, causing major disruption to daily life, poisoning water sources or collapsing buildings.
Occurs at constructive plate margins, destructive subduction margins.
What are volcanic gases? What are their impacts? Where do they occur? - Volcanic Hazards
Volcanic gases are toxic gases released by eruptions (CO2, SO2) which can be deadly to life and may cause significant damage. Can also form volcanic fog, irritate eyes/lungs/nose/throat.
Occurs at all types of volcano.
What is acid rain? What are its impacts Where does this occur? - Volcanic Hazards
Acid rain is when CO2/SO2 combines with water in the atmosphere to create sulphuric or carbonic acid. This pollutes surface water, damages crops and enhances weathering.
Occurs at all volcanoes.
What are mudflows/lahars? What are their impacts? Where do they occur? - Volcanic Hazards
Lahars are very thick mudflows formed when ash, rock and mud combine with rainwater. They travel very quickly and can result in major damage to the environment and structures in their path.
Occur at composite volcanoes at subduction boundaries.
What hazards result from frequent, mild, basaltic eruptions? - Volcanic Hazards
Frequent, mild, basaltic eruptions produce: lava flows, tephra, volcanic gases and acid rain.
What hazards result from explosive, andesitic and infrequent eruptions? - Volcanic Hazards
Lava flows, lahars, pyroclastic flows, acid rain, nuées ardentes, ash fallout and tephra.
What are the 4 ways in which hazards may be mitigated? - Volcanic Hazards
Monitoring - watching hazard formation
Prediction - predicting where/when a hazard may emerge
Protection - taking measures to protect vulnerable areas
Planning - planning how to survive in the event of a hazard
What methods can be used to predict and monitor volcanic hazards? - Volcanic Hazards
Looking at historical records to predict when hazards may occur, using seismometers that may detect seismic activity (indicating an eruption), measuring for ground deformation with tiltmeters, observing whether a change in gas concentration has occurred with equipment, measuring temperature of groundwater to indicate whether eruption will occur, map the impacts of previous hazards.
