Volcanic Hazards Flashcards
What is meant by a primary hazard?
Hazards that are directly related to the volcano and its eruption (e.g. lava flows, ash falls and gas clouds)
What is a pyroclastic flow?
A mixture of hot rock, lava, ash, and gases arising from a volcanic eruption that moves at rapid speed along the ground
What is tephra?
Rock fragments ejected during volcanic eruptions
What is a nuee ardente?
A dense, rapidly moving cloud of hot gases, ashes and lava fragments from a volcanic eruption (a type of pyroclastic flow)
What is meant by a secondary hazard?
Hazards that occur due to the occurrence of another, primary hazard. They are indirectly related to the volcanic event
What is a lahar?
A destructive mudflow which occurs as a result of a volcanic eruption
What is a tsunami?
A large wave triggered by seismic activity
What is acid rain?
Volcanoes eruption suphirpus gases which can result in acidic rainwater
How many people are estimated to be at risk of volcanic hazards worldwide?
500 million
What are some primary hazards of volcanoes?
Lava and pyroclastic flows. Tephras. Nuee ardentes. Ash fallout and volcanic gases
What are some secondary hazards of volcanoes?
Lahars. Volcanic landslides. Tsunamis and acid rain
What is meant by intraplate?
In the middle of a plate, away from the margins
What % of volcanic activity is found at plate margins?
95%
What are hawaiian eruptions?
Effusive and produce basalt lava which relatively high temps (1100-1250°C). Lw silica content (<52%). Less viscous. Spreads over long distances (over 20km at speeds of 50km/h)
What are plinian eruptions?
More explosive. Produce andesitic and rhyolitic lava. Lower temps (600-1000°C). Higher silica content (>69%). More unpredictable
What are pyroclastic flows?
Dangerous mixture of hot rock, lava, ash and gases. Can move at speeds of 200m/s and are typically 350-1000°C
What are subduction zones?
Zones where thin, dense oceanic crust is forced beneath thicker, less dense continental crust at a destructive plate boundary
Why is ash an issue for humans?
Covers a large area, often thousands of kms. Highly abrasive so impacts breathing abilities, and disrupt machinery. Can block out sunlight, reducing visibility and temperatures
What is a shield volcano?
A volcano with gentle sloping sides, characteristic of fluid basaltic lava
What is a caldera?
A large volcanic crater often formed following a highly explosive eruption where the summit of the volcano is removed
What are hotspots?
Sites where mantle plumes rise up through areas of thin crust, causing volcanic activity in areas away from plate boundaries
What is ground deformation?
The change in shape of the ground before or after a volcanic eruption; often it is due to the movement of magma below the surface
What are short-term responses to volcanoes?
Depend on the magnitude and the vulnerability of local people. Evacuations and deployment of emergency services. International aid/help
What are long term responses to volcanoes?
Preparedness, mitigation, prevention and adaption. Hazard maps and monitoring. Alert systems
