Volcanoes Flashcards
Types of lava flow speeds and temperatures
-Basaltic flows at speeds up to 3m/s and temperatures of 1250 degrees.
-Andesitic flows at roughly 0.3-0.5m/s and temperatures of 1000 degrees.
-Rhyolitic lava flows at no more than a few meters per hour and is erupted at 800 degrees.
Volcanic Gas example
-1n 1979, almost pure CO2 was released during the Dieng eruption, killing 175
Lahars example
-After the 1985 eruption of the Nevado del Ruiz Strato Volcano in Columbia, four lahars flowed through the town of Armero killing 20,000 of the 29,000 inhabitants.
Climate change example
-The 1991 erpution of Mt.Pinatubo released 20 million tonnes of SO2 into the atmosphere, reducing temperatures by up to 1degrees for 3 years after the eruption.
-In 1815, Mt.Tambora erupted with a VEI 7, putting an enormous amount of volcanic ash into the atmosphere. This led to the ‘Year without a summer’ which had the coldest summer temperatures on record between 1776 and 2000.
Tsunami example
-During the 1792 eruption of the Unzen Volcano in Japan, a flank collapsed into the ocean causing a tsunami that killed 14,000+
Eyjafjallajökull Stats
-Iceland had a population of 318,041
-Iceland had a GDP of $13.75 billion
-GDP per capita of $41,000
-The initial eruption was effusive, and the lava was relatively viscous.
-The second phase was much more explosive, and created a plume of ash that rose 8km high.
Eyjafjallajökull Prediction
-The eruption was predicted by monitoring a significant increase in seismic activity in the area. Seismic activity started at the end of 2009 and increased in intensity until the eruption.
-200 earthquakes occurred between June and August 2009, compared to a total of about 250 earthquakes between September and August 2009.
-The unusual seismic activity along with crustal displacement gave geophysicists evidence that magma was flowing into the magma chamber, indicating an eruption was imminent.
-Eyjafjallajökull erupted in 960, 1612 and 1821, giving researchers historical data to work with.
Eyjafjallajökull prediction evaluation
-Due to seismic activity, the point of eruption and increased risk of eruption were recognized, however the lack of proper historical data made pinpointing an exact date and time difficult and no VEI was predicted.
-This is no fault of theirs as volcanic eruptions rarely have good historical data, hence such difficulties are inevitable.
-Prediction methods haven’t really changed.
Eyjafjallajökull preparation
-Multiple primary schools practice regular evacuation drills.
-Folk story of ‘Katla the Witch’ warning of dangers of an eruption.
-2006 plans made for how to evacuate large populations of southern Iceland, not needed.
-500 families to be evacuated, but all returned after 24 hours
-Livestock moved inside to protect them from ashfall
-2019, new plans put in place in light of Eyjafjallajökull for other possible eruptions.
-Best preparation technique was that no one lived on the glacier or near harms way.
-Plans put in place to halt all plane journeys when ash concentrations reach more than 4mg per cubic metre.
-The airborne ash concentration limits were unnecessarily cautious, leading to an excessive amount of flights being grounded.
Eyjafjallajökull monitoring
-Icelandic meteorological office (IMO) operates monitoring systems.
-56 seismic stations.
-70 continuous GPS stations to monitor ground displacement. Detected as much as 5mm of displacement a day in the lead up to the eruption.
-Automated network or hydrological stations, measuring the discharge and temperature of meltwater-fed rivers.
-Ash fall monitoring and meteorological observations were used to track local ash’s dispersal. London Volcanic Ash Advisory centre (VAAC) played a crucial role in forecasting the ash clouds spread.
-LIDAR helped track ash dispersion.
Eyjafjallajökull monitoring evaluation
-Seismic activity monitoring and land surface monitoring data provided concrete evidence subsurface magma was rising into the magma chamber.
-GPS data showed no evidence for summit deflation, indicator of steady flow of magma.
-Hydrologic stations detected Jökulhlaups before the April 13th eruption, effective
Hunga Tonga stats
-Population of 105,042
-GDP of $518 million
-GDP per capita of $4,900
-Eruption began in December 2021
-Volcano is part of the Tonga-Kermadec island arc and is at a subduction zone.
-Volcano is 65km north of Tongas main island.
-Eruption climaxed on 15/1/2022, reaching a VEI 5
-Produced a series of four underwater balsts, displacing 10 cubic kilometres of material triggering several Tsunamis.
-41m high waves hit the uninhabited island of tofua, 27m high waves hit main island of Tonga.
-7 died, 4 in Tonga, 2 in Peru and 1 in Fiji
Hunga Tonga Prediction
-Very little prediction due to it being one of many underwater volcanoes in the area.
-DOES-17, seismic data and DART buoys used for short term monitoring/prediction.
Hunga Tonga prediction evaluation
-Last full eruption was in 2015, so should have had more prediction due to frequency of eruptions.
-2015 eruption ended with no casualties and no major damage, this may have inspired complacency.
-Absolutely can be said to be poorly predicted.
Hunga Tonga Preparation
-Low-lying coastal communities in Tongatapu Islands (where 60% of Tonga’s population lives) moved to higher ground
-Many people had experience from previous eruptions.
-Many education programmes like the DRR (disaster risk reduction) program.
-Closest populated island to the volcano was 64km away, so no risk of primary hazards, so little preparation necessary.
Hunga Tonga monitoring
-Tonga Geological services (TGS) and global seismometer networks (e.g. USGS etc) tracked seismic activity around Tonga.
-GPS stations and InSAR detected changes in land elevation, indicating magma rising into magma chamber.
-Infrared sensors(MODIS,VIIRS and GOES satellites) detected increased thermal activity.
-Cloud and ash monitoring was conducted by the Himawari-8 satellite (Japan) and the GOES-17 satellite (US).
-Tsunami buoys and tide gauges measured underwater activity and detected increased concentration of volcanic gasses.
Hunga Tonga monitoring evaluation
-Tonga had limited seismic stations, making it hard to pinpoint deep seismic activity.
-No direct ocean sensors near the volcano to measure magma build-up before the eruption, limited ability to asses real time changes.
-Due to the submarine nature of volcano, it wasn’t possible to measure ground deformation.
-NASAs OMPS detected 400,000+ tonnes of SO2 released, good indicator of volcanic activity.
International collaboration of DART buoys and tide gauges successfully measured pacific waves in 100+ locations.
-The eruptions pressure wave was recorded globally on various barometers and infrasound sensors, providing valuable data on its explosive power. However, lack of underwater sensors undermined accuracy.
-The scale of explosion exceeded all predictions, catching scientists off-guard. therefore monitoring was relatively ineffective/useless.
