The Icelandic Met Office has released an Official Bulletin about the possibility for an upcoming eruption at Þorbjörn on the Reykjanes Peninsula in Iceland.
Þorbjörn belongs to a class of volcanoes that I normally like to call Unknownabunga, one of all of those volcanic features in Iceland that pretty much nobody knows anything about, until they all of a sudden erupt out of the blue.
Currently it is not certain if Þorbjörn is a standalone volcanic fissure (central volcano), or is part of a wider known central volcano called Svartsengi. This will probably become clearer in a few hours as we get around to plotting things and checking against more well-known culprits on the Reykjanes Peninsula like Svartsengi.
So far both we and IMO are happy to call the volcano Þorbjörn and are treating it as a standalone unit. Suffice it to say that we are in for a possible treat.
For anyone who wishes to go to see the possible future eruption I recommend A) that you go quickly since this will close down Keflavik International Airport as soon as it starts, and B) that you head all instructions from the helpful and very competent local authorities.
Currently this has been an ongoing seismic episode with tectonic and volcano-tectonic signals, and marked inflation as evidenced on INSar.
We will update this article as news comes along, and there will be a new article as soon as we are done with the usual juicy plots so that we have something solid to interpret.
Iceland Met Office Bulletin in full
(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION — VONA
(2) Issued: 20200126/1715Z
(3) Volcano: Reykjanes (371020)
(4) Current aviation colour code: YELLOW
(5) Previous aviation colour code: green
(6) Source: Icelandic Meteorological Office
(7) Notice number: 2020-164
(8) Volcano location: N6349 W02243
(9) Area: Reykjanes Volcanic Zone
(10) Summit elevation: 140 M
(11) Volcanic activity summary: Change to yellow code for Reykjanes – ICAO 371020,
because of signals above normal background. GPS-system and InSAR images indicate rapid rise of the surface around
Reykjanes volcano system has ICAO location N6349 W0226 but Mt. Thorbjorn, is located seven nautical miles to the east at N6352 W02226.
(12) Volcanic cloud height: N/A
(13) Other volcanic cloud information: N/A
Possible magma accumulation beneath Mt. Thorbjorn on Reykjanes peninsula.
• Inflation has been measured the last few days.
• An earthquake swarm has been ungoing during the same period.
An inflation has been measured since January 21st and it‘s centered just west of Mt. Thorbjorn on Reykjanes peninsula. The inflation is unusually rapid, around 3-4 mm per day and has accumulated to 2 cm to date. It has been detected both on continuous GPS stations and in InSAR images. The inflation is most likely a sign of magma accumulation at just a few km depth. If the signal is indeed a magma accumulation it is very small, first volume estimate is around 1 million cubic meters (0,001 km3).
This is the conclusion of a meeting held with the Scientific council of the Civil Protection at the IMO this morning.
Accurate measurements of crustal deformation on Reykjanes peninsula span appoximately three decades. During this period no comparable signal has been measured. This is unusual for this period. An earthquake swarm has been ongoing, since January 21st, alongside the deformation signal just east of the inflation center (northeast of Grindavík). The largest earthquakes occurred on January 22nd and were of M3,7 and 3,6. They were felt widely on the Reykjanes peninsula and all the way up to Borgarnes region. The earthquake swarm is currently in decline. Swarms like this are common and not unusual by itself in the area.
The fact that an inflation is occurring alongside the earthquake swarm is a cause for concern and closer monitoring.
The inflation is occurring on plate boundaries and within the volcanic system of Svartsengi which is either considered a separate system or part of the Reykjanes volcanic system. The last known eruption was during Reykjanes fires, which occurred between 1210-1240 AD. Within that period a several eruptions occurred within that system, thereof there were three eruptions in Svartsengi system. The eruptions were effusive (non-explosive) fissure eruptions erupting on 1-10 km long fissures. No explosive eruptions are known from this system. The largest eruption in the swarm, from 13th century, formed Arnarseturshraun lava (estimated 0,3 km3 and 20 km2). The duration of these eruptions are usually from a few days up to several weeks. Seismic activity is very common in this area and is linked to the plate boundaries, geothermal activity and possible magma intrusions. The largest earthquakes measured in this area are about M5.5.
For more information Catalogue of Icelandic volcanoes.
The activity has only been ongoing for a few days and it is uncertain if it will escalate to more serious activity. Based on current information, the following scenarios are considered possible, without stating which is most likely or within what timeframe.
1. If the inflation is due to magma accumulation:
• Magma accumulation will cease soon without further activity.
• Magma accumulation continues for some time without further activity.
• Magma accumulation will lead to a magma intrusion.
• Magma accumulation will lead to magma intrusion and eruption (effusive fissure eruption).
• Magma accumulation triggers seismic activity with larger earthquakes (up to M6.0).
- If the inflation is not caused by magma accumulation:
• The inflation might be linked to tectonic activity and lead to larger earthquakes (up to M6.0).
The Civil Protection has declared Uncertainty phase.