Fagradalsfjall volcano update: Activity oscillates like heartbeat from almost absence to spectacular lava overflows

Thu, 19 Aug 2021, 17:42

17:42 PM | BY: T

Eruption in Iceland this evening (image: RUV live webcam)

Oscillating tremor reflecting the regular magma surges (image: IMO)

The eruption continues with no signs of ending, even though it has been going through rhythmically alternating phases of very low to very high levels. Roughly every 24 hours, it changes from one to the other extreme.
When it is high, the crater is filled with a lava lake that overflows on its rims and produces spectacular flows, as can be seen in the recent video below or in the view of the webcam right now (attached); when it is low, there is usually no visible activity at the surface.
Video:

Volcanologist Þorvaldur Þórðarson explained that these lava pulses are likely caused by large gas bubbles rising through the magma in the underground feeding system, pushing the magma out of the vent onto the surface.
Since these lava surges come at very regular intervals, these large gas bubbles must rise in very orderly pattern. Nature likes such regular processes and creates order,- think of the rhythmic behavior of geysers, for example.
The gas bubbles that are responsible for the peaks of activity at Fagradalsfjall are of course orders of magnitude larger than most similar phenomena. Likely, they originate at the top of the magma source in the upper mantle at 15-17 km depth, and once large enough to overcome a critical threshold of some sorts, they start rising and pushing the magma column upwards, resulting in the surface activity seen a short time after.