A large fissure has opened on the Reykjanes peninsula 2.42 miles (3.9km) wide. Lava is already spreading over a large area.
Police in Iceland have declared a state of emergency after a volcano erupted, forcing homes to be evacuated.
The eruption on the Reykjanes Peninsula, in southwest Iceland, is the sixth outbreak since December.
Iceland’s meteorological office recorded increased seismic activity and earthquakes at the volcanic hill, Sundhnukar, days before the volcano erupted.
A large fissure has opened up nearby, at the Sundhnukagígar crater north of Grindavik, with lava flowing both east and west.
One estimate by the country’s Met Office suggests “the lava flow has travelled about 1km in 10 minutes”.
Experts also said the total length of the fissure was about 2.42 miles (3.9km) and had extended by 1 mile (1.5km) in about 40 minutes.
Recent studies showed magma accumulating underground, prompting warnings of new volcanic activity in the area south of Iceland’s capital, Reykjavik.
The local police chief for the area has declared a state of emergency.
