volcanic hazards Flashcards
what is an active volcano
a volcano that erupted in the last 10,000 years
eg: Mount Etna, Italy
what is a dormant volcano
a volcano that hasn’t erupted in 10,000 years but is expected to erupt again
eg: Mount Fuji, Japan
what is an extinct volcano
a volcano that isn’t expected to erupt again
eg: Castle Rock Edinburgh, Scotland
characteristics of volcanoes at constructive margins
- usually shield volcanoes
- produce basaltic lava: dark lave hot (1000 degrees celcius), low viscosity
- frequent weak eruptions
- wide sloped volcano/shield volcanoes
- low gas content
- underwater margins: magma rises to fill spaces left by plates to form ocean ridges
- land margins: form rift valleys that thin out and allow lava to pass through
characteristics of volcanoes at destructive margins
- usually composite volcanoes
- produce andesitic and rhyolitic lava : cooler with higher viscosity
- infrequent violent eruptions
- steep volcanoes
- high gas content
name 6 volcano hazards
- pyroclastic flows: mix of super heated gas, ash and volcanic rock that travel far (10km-15km) at high speeds(80 km/h) and destroy everything in their path
temperature: 800 degrees Celsius Pompeii - lava flows: speed depends on volcano slope and lava viscosity. typically lava flows are slow but destroy anything in their path
- volcanic gases: carbon dioxide/sulphur dioxide released by lava that make it difficult to breathe
- tephra(pyroclastic and ash fall out): material that is ejected from the volcano and falls to the ground. ranges in size that can damage/kill or make it hard to breathe
lahars(mudflows): occur when tephra mixes with large bodies of water - 1985 Amero Tragedy
acid rain: volcanic gases react with water vapour which damages ecosystems
acidity of 4
how is the magnitude of volcanic hazards measured
measured using the Volcanic Explosivity Index which grades volcanoes on a scale of 0-8 based on the amount and height of material ejected.
-Eyjafjallajokull was a 3
-Mnt St Helens was a 5
Hawain volcanoes are 1
-Yellow Stone was 10
what is the importance of the frequency of volcanic events
typically volcanoes with less frequent volcanic eruptions are larger in magnitude
randomness vs regularity of volcanic events
some volcanoes will erupt at regular intervals while others may be dormant for a long time and then erupt several times
estimated that 50 to 60 volcanoes erupt per year
predictability of volcanic events
- shape, ground deformation monitored with lasers and tiltmeters
- small earthquakes show movement in magma
- Sulphur in the air can be measured with gas spectrometers
short term responses
occur immediately after the event like
evacuations and emergency supplies
volcano case study :
location
date
plate margin
volcano type
- Iceland Eyjafjallajökull
- 20th March 2010
- constructive north American and Eurasian plate
- composite volcano
4 economic impacts of the Eyjafjallajökull volcano eruptions
- airlines lost £130 million per day
- European tourism lost between £5-£6 million
- £80 million loss for Iceland
- Nissan halted production as parts couldn’t be imported from Iceland- globalization/TNC
3 social impacts of the Eyjafjallajökull volcano eruptions
- 0 deaths: volcano erupted 75 miles from capitol
- people had to wear goggles and masks due to the thickness of ash
- flights were delayed and cancelled
4 environmental impacts of the Eyjafjallajökull volcano eruptions
- temperature rises killed fish
- lava and ash rich soils are good for agricultural use
- eruption caused ice on volcano to melt which caused floods in southern Iceland on the 14th of April
- plankton bloom triggered by dissolved iron deposited by volcano
