The land below Vatnajökull glacier has drifted apart by 20 centimeters (8 inches) since the seismic activity and magma flow began in Bárðarbunga volcano, which lies underneath the northwestern part of the glacier, one week ago.
“The continental drift is two centimeters per year, so this is ten times the [natural] continental drift,” explained geophysicist Þóra Árnadóttir from the University of Iceland’s Earth Science Institute to ruv.is.
The 25-km (15-mile) channel formed by the magma has now stopped stretching to the northeast. Þóra believes this is either caused by an obstacle or, more likely, because the influx of magma has decreased.
In the one week since the activity began, approximately 5,000 earthquakes have been picked up by sensors, the largest of which was of a 4.7 magnitude and hit shortly before midnight on Thursday. A 3.5 earthquake hit at 6 pm yesterday.
The large quakes are believed to be caused by the magma chamber depressurizing, by the strain from the channel the magma has formed—or both. The caldera appears to be sinking.
According to a model made by the Earth Science Institute, approximately 200 million cubic meters (7.1 billion cubic feet) of magma has been flowing underneath the glacier in the past week. “The volume has doubled in just the last two days,” stated Þóra.