The Icelandic Meteorological Office has changed the aviation colour-code of Hekla volcano from green to yellow, signifying elevated unrest above a known background level.
Since 10 March 2013, at least seven micro-earthquakes, ranging in size from magnitude 0.4 to 1, have been detected over a small area ~4.5 km to the north-east of the volcano's summit. Sourced mainly at 11 to 12 km depth, these earthquakes have a high-frequency character suggestive of brittle fracturing rather than magma movements. At Hekla, such a clustering of earthquakes in time and space is unusual in between eruptions.
Continuous measurements of borehole strain and ground-based GPS show no changes in crustal deformation. The only measurable change is increased earthquake activity, although the earthquake rate is too low to assess whether this episode has peaked already. The change from green to yellow is a precautionary step due to increased earthquake activity. To date, there are no observable signs that an eruption of Hekla is imminent.
