A series of earthquakes that heralded the eruption also continued: On Thursday morning, a quake with a magnitude of 4.6 was measured on the peninsula, according to data from the Icelandic Meteorological Authority.
The number of tremors, however, has decreased noticeably since the eruption, according to the authority.
The eruption started on Wednesday afternoon near the mountain Fagradalsfjall. Scientists expected one due to earthquakes and associated underground magma movements. There is no major danger to people or the surrounding area, according to findings so far.
The island state's government also remained calm, with Prime Minister Katrín Jakobsdóttir speaking of a "relatively small" eruption.
"We've been expecting an eruption somewhere in this area since the series of earthquakes started last weekend," Iceland's premier was cited as saying in a statement on Thursday.
"What we know so far is that the eruption does not pose any risk to populated areas or critical infrastructure," she added.
It is still unclear how long the eruption will last. An eruption on the same peninsula last year saw lava fountains shooting upwards for months. The natural spectacle attracted countless volcanologists, hikers and travellers.
This time, too, curious onlookers have made their way to the eruption site, with media reports speaking of thousands of people.
A helicopter pilot told broadcaster RÚV that the number of requests for helicopter tours has skyrocketed. So far, however, the airspace over the volcano is still closed.
The government also advised hikers to stay off the area due to the gas development. Iceland's chief police officer Vídir Reynisson, in comments to RÚV, said that the kilometer-long route to the eruption site was only suitable for experienced hikers.
The area is relatively sparsely populated, but is home to the country's most important airport, which handles practically almost all air traffic to and from the island.
According to the government, operations have not been impacted by the eruption so far.
