The quake near the country's Bárðarbunga volcano may have moved underground magma north to beneath the Askja volcano, and could trigger an eruption. British and Icelandic scientists said 50 million cubic meters (1.76 billion cubic feet) of magma, or molten rock, have moved in the most recent 24-hour period.
"It's moving at about 4km a day towards Askja, and if it keeps going it could get there in a few days. We know there is a lot of molten rock sitting under the ground beneath Askja, which is a major volcanic system. If this molten rock hits that, we know it is likely to trigger it to erupt," Bob White, University of Cambridge professor, told the BBC.
An eruption could cause massive amounts of ash to enter the air, in addition to "fire fountains of lava" on the ground, spectacular plumes of lava spouting from the earth. An eruption of Askja last occurred in 1875 -- the ash killing crops and livestock, and prompting a wave of migration from the northwestern part of Iceland.
The ash fall from the country's 2010 Eyjafallajokull eruption closed airports across Europe, with planes unable to fly through the dense ash in the atmosphere.