COPENHAGEN, Denmark — A volcano in southwestern Iceland erupted on Thursday, the meteorological office said, spraying red-hot lava and smoke in its sixth outbreak since December.

The total length of the fissure was about 2.42 miles and had extended by nearly a mile in about 40 minutes, the Icelandic Met Office, which is tasked with monitoring volcanoes, said in a statement.

Livestreams from the volcano on the Reykjanes peninsula showed glowing hot lava shooting up from the ground, their…