Eerie blue flames flared from the ground on Hawaii's Big Island on Tuesday night (May 22), marking a rarely seen phenomenon that can arise during volcanic eruptions.

When red-hot lava buries plants and shrubs, the burning vegetation produces methane, a colorless gas that burns blue, according to the U.S. Geological Survey (USGS).

When methane is heated, it can seep into voids below the surface — in this case, the cracks on Kahukai Street in the residential area of Leilani Estates. Heated methane can explode, but when it was ignited on Tuesday night, its blue flames simply burned out of the fractures in the road, several feet away from the lava, the USGS reported. [Photos: Fiery Lava from Kilauea Volcano Erupts on Hawaii's Big Island]

"It's very dramatic. It's very eerie," Jim Kauahikaua, a USGS scientist, told the Associated Press. This is only the second time in his career that he's seen blue flames during an eruption, Kauahikaua said.

These eerie blue flames are actually burning methane.
These eerie blue flames are actually burning methane.
Credit: U.S Geological Survey

About 2,000 people have evacuated from Leilani Estates and adjacent neighborhoods since the Kilauea volcano began erupting in early May. More than 20 fissures have opened, pouring lava and volcanic gases such as sulfur dioxide into the area.

One man was even hit on the leg by a "lava bomb" — a glob of molten lava that was ejected from the volcano — and lived to tell the tale. The eruption has destroyed about 50 buildings, including about two dozen homes.

This map shows current and historical lava flows on Hawaii's Big Island. The blue flames burned in the Leilani Estates. The light purple areas on the map show where lava flows erupted in 1840, 1955, 1960 and 2014-15. The pink and red areas show where lava has flowed, and is flowing, during this eruption.
This map shows current and historical lava flows on Hawaii's Big Island. The blue flames burned in the Leilani Estates. The light purple areas on the map show where lava flows erupted in 1840, 1955, 1960 and 2014-15. The pink and red areas show where lava has flowed, and is flowing, during this eruption.
Credit: U.S Geological Survey

Original article on Live Science.