Hawaii's Mauna Loa, the world's biggest active volcano, erupts after 38 years

In this aerial photo released Monday by the U.S. Geological Survey, a volcano on the Big Island of Hawaii is visible from the air.

U.S. Geological Survey via AP

The eruption of the world's largest active volcano caused smoke to fill the night sky in Hawaii.

The long mountain exploded at 11:30 pm local time on Sunday. The U.S. Geological Survey said it had been showing signs of unrest.

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"hazardous eruption is imminent, underway or suspected" is the federal agency's definition of the volcano alert level.

There had been no calls to evacuate. The eruption doesn't appear to be threatening downslope communities according to the mayor. The Old Kona Airport in Kailua-Kona and the Ka'u gym in Pahala were opened as shelters for those who evacuated.

Mauna Loa is taller than Mount Everest

There are 15 volcanoes in the Hawaiian Islands. It makes up nearly half of the island of Hawai'i. It's more than a thousand feet taller than Mount Everest and is found at the bottom of the sea. Only a small portion of the island is above sea level.

Between 600,000 and a million years ago, the volcano's first lava flows began. According to scientists, the Mauna Loa probably emerged above sea level 300,000 years ago.

The eruption ends Mauna Loa's longest recorded quiet period

Records of eruptions began in 1843. It took three weeks for the last one to happen. The biggest city on the big island is Hilo.

One of the most destructive eruptions happened in the spring of 1868, when 4,000 acres of land were destroyed and 77 people were killed in a series of earthquakes. One of the worst natural disasters in Hawaiian history happened when the lava flow lasted five days.

The inside of the summit caldera is shown in the image. According to the U.S. Geological Survey, lava flows were contained within the summit area and so far were not threatening nearby communities.

USGS Hawaiian Volcano Observatory via AP

The lava appeared to be contained and there was no sign of it leaving the summit. The flow of the lava in the early stages of the eruptions can change quickly.

It can be dangerous to descend the volcano's steep slopes if it erupts at a high rate. The U.S. Geological Survey said it can produce fast- moving and long- travelled lava flows.

Volcanic gas and fine ash can be carried by winds to nearby communities.