Today marks 30 days from the start of the Fagradalsfjall eruption on the Reykjanes peninsula. Originally one of the smaller eruptions in recorded history, the lava flow in the eruption has been stable and even increased slightly in the past week or so, according to new data from the University of Iceland’s Institute of Earth Sciences.
University of Iceland geologists state that the average lava flow for the first 30 days is 5.6 m3/second and that compared to other recent eruptions, the flow is relatively stable. There’s even been a slight increase for the past week or two. Despite this increase, the flow is only half of the average flow of the first 10 days at Fimmvörðuháls in 2010, which itself was a relatively small eruption. Compared to the large 2014 Holuhraun eruption, the current eruption only produces 6-7% of the average lava flow for the six-month duration. A comparable lava flow occurred in the Surtsey eruption, starting in April 1964 and lasting until June 1967.
The latest data on the lava field’s size and the average lava flow state that the flow from all craters in a six-day period from April 12-18 was on average just under 8 m3/second, which confirms that the eruption’s lava flow is increasing as more vents open up on the erupting fissure. The lava field is now around 0.9 km2.
Below is an overview of the lava flow issued by the University of Iceland’s Institute of Earth Sciences.
On Saturday, yet another eruption opening opened up on close to earlier eruption points. It’s a small opening located in the lava field close to another crater in the area. This likely won’t change much in the development of the eruption but what’s interesting is that scientists may have discovered indicators for new eruption points opening. At around 13.20 on Saturday, natural hazard experts with the Icelandic Met Office noticed that the strength of tremors in the vicinity of the eruption dropped close to the eruption. This had happened before, for an hour or longer, before new vents opened up. Once the natural hazard experts on duty noticed the tremor strength dropping, they notified emergency responders on the scene, asking them to monitor the lava flow closely and watch for new vents. Shortly afterwards, a notice came back from the eruption, notifying the met office that a new vent had opened up.
There’s a precedent for the tremor strength dropping before new vents opening up but there are also some examples of the tremor strength dropping without new vents opening. While tremor drops can indicate new vents opening up, they don’t indicate the new vent’s location. Natural hazard experts at the Icelandic Met Office will continue to monitor the eruption, particularly how and when new vents open up and what precedes new openings.