Following two strong tremors, fear about the eruption of Iceland's biggest volcano rises. According to the Icelandic Meteorological Office, two earthquakes measuring 4.6 and 4.5 magnitude shook the crater of Katla on Monday.

Iceland Review notes that the tremors are the strongest to hit the crater since 1977. With 20 eruptions recorded since the year 930, Katla remains one of the country's most-feared volcanoes. Of the total number of eruptions, only 18 managed to penetrate the ice cap covering the central crater of the volcano.

The ice cap delays the lava flow in case of eruption by containing lava for up to a few minutes when eruption occurs. Experts note that the volcano, which stands at 1,500 meters, usually erupts every 50 years. Its last noted eruption occurred in 1918, causing hazardous flooding and ash fall.

Even so, volcanic activities have been observed for the past years.

"The last large eruption in Katla was in 1918, but in the meantime there have been three events that indicate volcanic activity underneath the glacier. First in 1995, then in 1999 and most recently in 2011 when a glacial flood in Múlakvísl river took out a bridge on the main road," Dr. Páll Einarsson, professor at the University of Iceland Institute of Earth Sciences told Iceland Monitor.

The Icelandic Meteorological Office and Scientists at the University of Iceland Institute of Earth Sciences have been monitoring the volcano. Although they said eruption is imminent, they cannot eliminate the idea that it may explode anytime.

"Such summertime increases in seismicity are common at Katla and the ongoing activity within the caldera is similar to summertime unrest observed in 2012 and 2014," the meteorological office confirmed to CNN. "Measurements around Katla are not detecting signs of increased ground deformation or seismic tremor, both of which could be indicators of magma movement."

Meanwhile, another volcano named Hekla is also being monitored and can also erupt anytime.