The world's largest active volcano, Mauna Loa in the US state of Hawaii, has erupted for the first time in nearly 40 years.

The US Geological Survey announced that the eruption began on Sunday.

The agency is warning the roughly 200,000 residents of the Island of Hawaii that "the early stages of a Mauna Loa rift zone eruption can be very dynamic, and the location and advance of lava flows can change rapidly."

The site of the eruption is far from residential areas, but local authorities on Monday urged people to be ready to evacuate if lava flows their way.

The volcano last erupted in 1984.
A local resident who has seen Mauna Loa erupt three times said people are worried because they do not know where the lava will flow or when the eruption will stop.

Local authorities say on their website that the island's two airports are operating normally, but urge passengers to check with airlines for the latest flight information.