Over the past two days the GPS station on Grímsfjall has been reporting some interesting data on what is going on inside Grímsfjall. But it appears that Grímsfjall is inflating at really fast speed at the moment. The movement is mostly upwards, as the station is located on the top of the mountain.
Currently the GPS station at Grímsfjall is reporting about 85mm movement upwards and about 5mm movement north (moving south). At last the movement east is about 10mm. But that gives the expansion site close to the GPS station, I would estimate rather rudely about 5 to 10 km from the SIL and GPS location. But it might be closer or longer. This is just a badly educated guess that I am doing here.
It is clear that if Grímsfjall continues to inflate at the same rate and it has been doing for the past few days and weeks it is going to erupt real soon. When is a good question as always.
Data: ISGPS GFUM