A volcano erupted under one of Europe’s largest glacier, Vatnajokull, is abating after it forced close Iceland’s main international airport, the second such volcano eruption in 13 months.

“It is likely that the eruption is dwindling,” Magnus Tumi Gudmundsson, a geologist at the Institute of Earth Sciences at the University of Iceland, told national broadcaster RUV. “What we are seeing is that it has slowed. It went down to being similar as the eruption in 2004 and in Eyjafjallajokull a year ago.”

The height of ash plume is diminished to 11 kilometers (6.8 miles) from 20 kilometers, according to the statement from the Icelandic Meteorological Office. Meteorologists used a new weather radar system to monitor the development.