Only weeks after the latest volcanic eruption in Iceland, the glacier volcano Grimsvötn is now threatening to erupt after being shaken by a strong earthquake.

On Thursday morning, 11th January, there was a strong earthquake under the Icelandic glacier volcano Grimsvötn, approximately 200 km east of Reykjavik.

The 4.3 magnitude earthquake occurred at a depth of just 100 metres and was the strongest since monitoring of the volcano began, which is classified as highly active. It erupts on average every 10 years.

Experts interpret the force and shallow depth of the earthquake as a precursor to an imminent, larger eruption. According to this, a glacial cavern filled with meltwater has likely burst and triggered what is known as a glacier run.

The release of pressure on the subsurface could encourage magma to rise from the depths, making a volcanic eruption more likely.

If large quantities of meltwater are also released, the eruption could be very explosive and hurl clouds of ash miles into the sky.

With a glacial volcano like Grimsvötn, a massive ice cap weighs down on the volcano. When the ice melts, highly explosive eruptions occur when magma comes into contact with water.

Even if they cannot say for sure that the mountain will erupt, volcanologists see the recent quake as an indication of an imminent eruption. This fear is supported by small swarm quakes that occurred shortly after the main one.

It was only in December that the spectacular volcanic eruption occurred along a kilometre-long fissure on the Reykjanes peninsula in the southwest of the island. Here, the problem was not meltwater floods and volcanic ash, but large quantities of lava.