The world's largest active volcano is erupting.

The eruption at Mauna Loa in Hawaii Volcanoes National Park began Sunday.

The Hawaiian Volcano Observatory said lava is flowing down one side of the volcano but is not a threat to any communities.

The eruption did lead to an ashfall advisory for early Monday.

Up to a quarter inch of ashfall could accumulate on parts of the Big Island.

The National Weather Service in Honolulu says people with respiratory illnesses should stay indoors -- and anyone outside should cover their mouth and nose with a mask or cloth.

Mauna Loa, which covers half the island, has erupted 33 times since 1843.

It's last eruption was in 1984, making this prolonged quiet period the volcano's longest in recorded history.