The Icelandic Meteorological Office (IMO) reported that on 17 November the Aviation Color Code for Öræfajökull was raised to Yellow because satellite images and photos showed that a new ice cauldron had formed within the caldera the previous week. The new cauldron was about 1 km in diameter and 15-20 m deep, and signified a recent increase in geothermal activity. Scientists conducted an overflight on 18 November; in addition, while on the ground, they took water samples, measurements of electrical conductivity, and gas levels at the Kvíárjökull outlet-glacier, a valley glacier on the SE flank of Öræfajökull. There was no obvious sign of flooding in the Kvíá river. A sulfur odor, which had been reported for about a week, was also noted. An increase in the seismic activity was recorded for the last few months (the largest earthquake, an M 3.4, occurred on the 3 October), but was low for the past few days. IMO noted that there were no signs of an imminent volcanic eruption, though there was considerable uncertainty about how the situation will evolve.

Geological Summary. Öræfajökull, Iceland's highest peak, is a broad glacier-clad central volcano at the SE end of the Vatnajökull icecap. A 4 x 5 km subglacial caldera truncates the summit of the dominantly basaltic and rhyolitic volcano. The extensive summit icecap is drained through deep glacial valleys dissecting the SW-to-SE flanks. It is the largest-volume volcano in Iceland, and was mostly constructed during Pleistocene glacial and interglacial periods. Holocene activity has been dominated by explosive summit eruptions, although flank lava effusions have also occurred. A major silicic eruption in 1362 CE was Iceland's largest historical explosive eruption. It and another eruption during 1727-28 were accompanied by major jökulhlaups (glacier outburst floods) that caused property damage and fatalities.

Source: Icelandic Meteorological Office (IMO)