Mauna Loa: Facts about the world's largest active volcano

Mauna Loa, the world's largest active volcano, erupted in Hawaii in spectacular fashion late on Sunday, marking its first eruption in nearly 40 years.

The volcano's awakening after decades of dormancy, has not, as of now, threatened any populated areas, but the US Geological Survey (USGS) has nonetheless put out its highest-level alert urging residents of Big Island, where Mauna Loa is located, to be cautious.

The USGS has also put out a code red aviation alert because of the plume of smoke released by the volcano and has warned that additional fissures could erupt, although unlikely.

In view of this rather rare eruption, we take a look at some facts about Mauna Loa.

Long mountain on Big Island:

Located on the south-central part of the state of Hawaii on Big Island, Mauna Loa, literally meaning 'Long Mountain' in Hawaiian, is a massive shield volcano that is so enormous that it occupies nearly half of Big Island.

It has a surface area of about 5,100 sq km and a submarine area that is even larger, and scientists estimate Mauna Loa's volume to be at least 75,000 cubic km.

A fiery relic:

Mauna Loa is ancient and scientists suspect it emerged above the sea level about 300,000 years ago.

Studies suggest that Mauna Loa has been erupting for at least 700,000 years, but records on eruptions, needlesss to say, have not been around for that long

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Mauna Loa's first documented eruption was in 1843, and since then, the shield volcano has erupted 33 times.

The most recent eruption, barring Sunday's, was in 1984, when lava flows from the mountain came within 7.2 km of Hilo, the largest population centre on Big Island.

A "gentle" giant:

Despite having erupted 33 times since its first documented eruption in 1843, eruptions in recent history have not caused fatalities, although the 1926 and 1950 eruptions did destroy a few villages.

Bombing an active volcano:

Although it may sound ludicrous and even downright insane, the US Air Force actually bombed Mauna Loa nearly a century back.

In 1935, lava from Mauna Loa threatened to contaminate the water supply for the seaside town of Hilo, home to around 20,000 people, prompting the US Air Force to spring into action.

However, instead of attempting to evacuate those in danger, the Air Force, on the advice of Hawaiian Volcano Observatory (HVO) founder Thomas Jagger, opted to bomb the lava tubes and the channels feeding the lava in a bid to prevent catastrophe.

The mission, interestingly, was headed by none other than future General and World War II hero George S Patton, and by Jagger's accounts, was a roaring success.

Indeed, observations suggested that that the lava, which was covering a distance 5,000 feet a day, had slowed to a speed of 1,000 feet a day, stopping entirely on January 2, 1936.

That being said, not everyone agreed that the bombing caused the slowdown, including Harold Stearns, a USGS official who flew on the mission.

"Though we are as yet unable to determine what effect the airplane bombardment achieved … I feel very doubtful that it will succeed in diverting the flow," Stearns had said back then, a conclusion that the USGS says is largely supported by modern science.

A secret eruption:

While all of Mauna Loa's eruptions in the recent past have become public domain knowledge, the US, back in 1942, had attempted to keep one eruption a "secret."

With World War II raging at the time, nighttime blackouts had been imposed on Hawaii to minimise the risk of bombing by Japanese war planes.

Hence, when Mauna Loa erupted on April 26, the US took efforts to keep the news secret, fearing that Japan, if it came to know, would use the bright glow of the lava at night to guide its warplanes to Hawaii.

The eruption was thus kept off news media, and according to the National Park Service (NPS), efforts were taken by the US Air Force to bomb lava tubes and check the flow of lava again.

While the efficacy of this operation also remains in doubt, lava flows from the eruption came to a stop on May 9, 1942.