The magma intrusion from Bardarbunga, which has reached the Holuhraun lavafield north of Dyngjujokull, is estimated to be only 2 kilometers beneath the surface, says Magnus Tumi Gudmundsson, geophysicist at University of Iceland. The magma could breach the surface in the existing lavafield, he says.
Newly formed crevasses in the Holuhraun lavafield were spotted yesterday. They are thought be the result of the rifting underneath, caused by the magma intrusion that has been propagating north from Bardarbunga since August 16. Gudmundsson was among the scientists who surveyed the area yesterday and today. The area where the new cracks are found, is ca. 1 km. wide and reaches 5 - 6 km north of the margin of Dyngjujokull glacier, towards the floodplain north of the Holuhraun lavafield which was formed in a 1797 eruption near Dyngjujokull. Cracks were also seen in the glacier´s edge as well as small cauldrons.
The intrusion is now at 2 km depth, says Gudmundsson. He says that rather then migrating upwards, the magma has so far sought out cracks and crevasses in the bedrock, caused by the rifting. The intrusion could very well stop without ever reaching the surface. It has now propagated into the Askja fissure swarm, but Gudmundsson considers it unlikely that it will reach the magma chamber underneath Askja; an eruption elsewhere would be a more likely scenario.
Due to the propagation of the dike intrusion towards the north, the Icelandic Met Office has raised the aviation alert status for Askja from green to yellow, meaning that a cause for concern is present, but no danger.
The cauldrons south of Bardarbunga which were spotted yesterday were likely caused by a small eruption that has now petered out, says Gudmundsson. The cauldrons were surveyed again today and had not changed. A likely scenario, says Gudmundsson, is that after a brief subglacial eruption, the magma had again started to flow towards the intrusion. 30 - 40 million cubic metres of water are thought to have melted and likely drained towards the Grimsvotn volcano, where a large natural reservoir exists.