Lava shot into the sky following a series of small earthquakes in recent weeks.
Swarms of earthquakes have been shaking the Reykjanes Peninsula for days.
"It is likely there will be an eruption in the future - we just aren't sure when or where."
Residents of St Vincent and the Grenadines have been advised to evacuate their homes.
Volcanic tremors continue to be recorded at Mt Ruapehu despite a drop in temperatures at the crater lake.
The heightened volcanic alert level on Mt Ruapehu has been described as a "kick in the guts" for one tourism business.
The heating has been accompanied by "bursts of volcanic tremor and a marked increase in the amount of gas".
A group of volcanoes in the Pacific might actually be separate vents of a single supervolcano, scientists have revealed.
A massive Icelandic volcano is set to erupt, experts in New Zealand and around the world have warned.