A summary of the events:
On August 16, considerable earthquake activity started under Bárðarbunga, a volcano in the northwestern part of Vatnajökull. Geologists immediately indicated that this might be the first sign of an upcoming eruption.
On August 23, excessive seismic activity indicated that an eruption had started but later that day scientists retracted the statement. It now seems likely that a small sub-glacial eruption did in fact take place, possibly on August 23, as new cauldrons indicate glacial melt.
Seismic activity has indicated that an intrusive dike has been moving north from the Bárðarbunga caldera towards the Askja volcano area. The earthquakes in the caldera have been getting bigger, some over 5.0 in magnitude.
On August 27, the Iceland Met issued a statement: "A cauldron [also known as a low or caldera] was observed in the glacier at 64°34,80' N and 17°21,30' W. The cauldron seems to be shallow, but many small crevasses/fractures. Ice thickness probably 400-600 m.“
Two minutes after midnight on August 29, a small fissure eruption started in the Holuhraun lava field, approximately 9 km (5 miles) north of Dyngjujökull, a Vatnajökull outlet glacier. First indications are that the lava streams out of a 1-km long fissure, about 15 km south of the Askja caldera, RÚV reports.
The eruption might move to the south, towards Dyngjujökull.
Webcams seem to indicate that the eruption is small and may already be subsiding.
Road and area restrictions that have been enforced over the last days are still in effect in the area north of Vatnajökull.