The first volcanic eruption in Mauna Loa since 1984 prompts ashfall caution for Hawaii's Big Island.

Mauna Loa hasn't erupted in nearly 40 years, prompting an ashfall caution for Hawaii's Big Island and nearby waters until 10 a.m. (3 p.m. ET).

Hawaii Volcanoes National Park's eruption doesn't affect downstream villages or planes to the island, the Hawaii Tourism Authority said on Monday.

The National Weather Service in Honolulu stated that fine ash and volcanic gas could be carried downwind by the winds,

 Which could cause a "trace to less than one-quarter inch" of ashfall to settle on certain portions of the island.

The Hawaii Volcano Observatory reports lava rushing into the volcano's southwest caldera or crater. 

The agency said that there is no imminent danger to adjacent towns and that no evacuations have been ordered.

As a precaution, two shelters have opened, even though "approximately half" of Mauna Loa eruptions stay in the summit area without affecting populated areas.

“People with respiratory ailments should stay indoors to prevent breathing ash particles,” the Honolulu office advised.

"Crop and animal damage possible. Infrastructure and equipment damage. Visibility decreases. Cleanup may be needed.”

Weather service said Ashfall can harm vehicles and buildings, taint water sources, disrupt sewage and electrical systems, and kill flora.