The effect is actually an optical illusion.

Blue Lava
Credit: Courtesy of YouTube

A video captured the phenomenon of blue lava tumbling out of the Kilauea volcano in Hawaii on Wednesday.

The effect, sometimes referred to as the "blue hour," occurs as the sun sets, causing light to refract off the glowing lava and creating this optical illusion of blue lava, the Telegraph reported.

Kilauea is one of the most active volcanoes on the Big Island of Hawaii, and it attracts tourists from around the world. Some adventurous visitors even hike the 7.4 miles round-trip through the national park where Kilauea is located just to catch a glimpse of the erupting volcano.

Ancient local legend says the goddess Pele inhabits the volcano that stands 4,190 feet above sea level.

Kilauea isn’t the only volcano to burn bright blue; Indonesia's Kawah Ijen volcano also appears to glow blue.

French photographer Olivier Grunewald revealed to Smithsonian Magazine that the lava is not blue, but rather contains blue flames, caused by burning sulfur.

"The vision of these flames at night is strange and extraordinary," Grunewald told Smithsonian, adding, "After several nights in the crater, we felt [we were] really living on another planet."