Posted by TW on July 14, 2018
Öræfajökull volcano in southeastern Iceland, the largest active volcano and the highest peak in Iceland, is showing clear signs of unrest with an inflation phase for at least a year and a half. The last eruptive episode of this volcano started in August 1727 and ended in May 1728.
The inflation is ongoing and is reflected by increased seismicity and characteristic deformation pattern, Icelandic Department of Civil Protection said July 13, after a series of meeting with scientists from The Icelandic Meteorological Office, The University of Iceland and Iceland Geosurvey.
There are no signs of a decrease in the inflation rate or the seismicity and the state of unrest persists despite a decrease in geothermal activity since last December.
The source causing the inflation is most likely injection of new magma, scientists said. The volume change since the start of the unrest is of the order of magnitude of 10 million m3 (about 0.2 m3/sec) comparable to the intrusion activity in Eyjafjallajökull some years before the eruption in 2010.
New resistivity measurements indicate the presence of geothermally altered rocks at shallow levels inside the caldera consistent with intermittent high-temperature geothermal activity as seen in many other volcanoes.
Referring to possible scenarios and hazards, scientists said that Öræfajökull is in a typical preparation stage before an eruption but the temporal evolution and the outcome is unknown. Increase in the geothermal activity with associated floods and gas release is a possible scenario.
Civil Protection preparedness:
- Civil Protection and earth scientists have held public information meetings regarding the unrest in Öræfajökull with both local population and tour operators in the area around Öræfajökull. Further meetings are planned in late September.
- An emergency evacuation plan to be used in case of a sudden eruption in Öræfajökull has been prepared. The plan is available here.
- Work on a response plan for volcanic eruptions in Öræfajökull is ongoing.
- The number of instruments for volcano monitoring has been increased on and around the volcano. Natural hazards specialists at the Icelandic Meteorological Office monitor changes in activity, they alert Civil Protection if they detect changes in the volcano´s activity.
- The Icelandic Meteorological Office, the Institute of Earth Sciences and Iceland Geosurvey in cooperation with the Iceland Glaciological Society have increased research efforts at Öræfajökull to deepen understanding of increased seismic activity, increased inflation of the volcano as well as changes in subglacial geothermal activity.
- Telecommunications operators have improved cell phone coverage in the area.
Volcanic hazardsProximal areas (<30 km / 18 mi distance from the source)
Hot, fast-traveling pyroclastic density currents are possible and are known to have reached the presently inhabited lowlands (in 1362 CE).
Large jökulhlaups cascading down the steep flanks of the volcano, disrupting transport along the principal road, and posing hazard to several farmlands, rural developments and Skaftafell national park.
Heavy tephra fall causing total darkness for hours and potential health hazards.
Volcanic lightning strikes.
Medial areas (30 - 150 km / 18 - 93 mi distance from the source)
Tephra fall causing total darkness for hours and transport (and communication) disruptions. It may also pose health hazards incl respiratory problems and damage to vegetation.
Distal areas (>150 km / 93 mi distance from the source)
Ash clouds on airline routes and airports causing disruption of air traffic.
Potential pollution from gas and aerosol clouds.
Precursory signalsIntense earthquake activity is expected prior to an eruption in Öræfajökull, partly because the volcano is situated on a cold thick crust, through which the magma needs to travel on its way to surface.
Historical records from the eruption in 1727 CE indicate that an intense earthquake activity occurred some days before the eruption. Archaeological excavation of farms ruined by the eruption in 1362 CE further supports these records. Walls show damages prior to tephra fall in the area, interpreted as earthquake damage.
AlertsThe Icelandic Met Office and Civil Protection Agency raised the aviation color code for the volcano from Green to Yellow on November 17, 2017, after a pilot flying over the area noticed a new ice-cauldron within the Öræfajökull volcano caldera. The alert was lowered back to Green on May 4.
The unrest was apparent from elevated seismicity, the development of a depression in the ice-surface (cauldron) within the caldera, and the presence of geothermal gases from a glacial river. The geothermal activity beneath Öræfajökull was assessed to be high relative to previous decades, IMO said.
Previous eruptionsThe last eruptive episode of this volcano started on August 3, 1727, and ended on May 1, 1728 (± 30 days). It had Volcanic Explosivity Index of 4 (on a scale of 1 - 7) and was responsible for deaths of three people.
Before that, the volcano started erupting on June 5, 1362 (± 4 days) and stopped on October 15, 1362 (± 45 days). This one had Volcanic Explosivity Index of 5 and was Iceland's largest historical explosive eruption. The volcano ejected huge amounts of tephra and destroyed the district of Litla-Hérað by floods and tephra fall. More than 40 years passed before people again settled the area, which became known as Öræfi.
Featured image credit: IMO
Thanks to: https://watchers.news