
An amazing photo of a dome-shaped lava formation has captivated the internet nearly 50 years after it formed.

In a throwback tweet, the US Geological Survey shared a stunning look at the rare symmetrical dome fountain created in 1969 during the 5-year-long Mauna Ulu eruption at the Kilauea Volcano in Hawaii.

From October 10 to 13 of that year, the dome grew to be over 30 feet tall, at some points even climbing as high as 65ft – and, while it might just look like a giant gaseous bubble, the experts say that wasn’t the case.

Another view in which part of the dome could be sliding away revealed an interior made entirely of liquid lava.

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In a throwback tweet, the US Geological Survey shared a stunning look at the rare symmetrical dome fountain created in 1969 during a 5-year-long eruption at the Kilauea Volcano in Hawaii. At the moment the incredible dome-shaped lava fountain was captured in the USGS photo, it was roughly 20 meters tall (65 feet)

Lava fountains such as that shown in the 1969 photo are formed as gas bubbles rapidly form and expand in the molten rock emanating from isolated vents, fissures, lava lakes, or lava tubes, causing a jet of lava to spew into the air, the USGS explains.

They can grow to staggering heights of over 500 meters, though they usually remain somewhere between 10-20 meters.

In 1969 alone, there were 12 fountaining events, with some reaching as high as 540 m (1,770 ft). These typically welled to their maximum height over the course of several hours, before collapsing again in a matter of minutes, according to USGS.

At the moment the incredible dome-shaped lava fountain was captured in the USGS photo, it was roughly 20 meters tall (65 feet).

While fountains themselves may not be all that unusual, this particular formation took on an uncharacteristically symmetrical shape.

While the fountaining episode that created the dome lasted just about three days, the eruption itself was far longer. It began months earlier, on May 24, 1969, and lasted until July 22, 1974. The eruption sent lava flows oozing into ‘Alae Crater, and even once into the ocean 12 km (7.5 mi) away. Above, such 'lava falls' can be seen pouring into the crater in 1969

The map (left) shows the incredible lengths to which the lava flows of the Mauna Ulu eruption traveled. Another view in which part of the dome could be sliding away (right) revealed an interior made entirely of liquid lava.

In a report detailing the years-long Mauna Ulu eruption on the east rift zone of the Kilauea Volcano, the USGS says the fountaining episode that formed the dome was quite unlike those before it.

It lasted for 74 hours, and was nearly twice as long as long as the nine prior fountaining episodes.

During the three-day period, the two compartments of the western vent area created a series of low, dome-shaped fountains, USGS said.

And, one stood out in particular.

‘A remarkably symmetrical dome fountain occasionally 20 m high but usually half that, often welled from the eastern compartment for periods of several hours,’ according to the report.

Above, a 300-meter-high lava fountain that formed during the Mauna Ulu eruption is shown on December 30, 1969

‘Most of the lava from this fountain flowed away from the vent, but some formed a narrow river that poured back into the western compartment.

‘Every few seconds, gases burst explosively from the western compartment, carrying spatter possibly derived from the lava drainback.’

A second photo shared in the report showed part of the dome sliding away, providing a glimpse at its liquid-lava core - revealing it was not ‘simply a large bubble.’

‘Mottled surface, caused by solidified crust interspersed with still-liquid lava, is typical of dome fountains,’ the experts noted.

WHAT WAS THE MAUNA ULU ERUPTION? A lava fountain that formed on June 25, 1969, is pictured. It lastd roughly 9 hours, and hit a maximum height of 220 m (500 ft) The Mauna Ulu eruption was a 5-year-long event at Hawaii’s Kīlauea volcano that lasted from May 24, 1969 until July 22, 1974. In its first year, the eruption spawned 12 fountaining events – one of which led to the formation of a stunning symmetrical ‘dome lava fountain’ in October 1969. ‘At the time,’ USGS says, ‘it was the longest-lasting and most voluminous eruption on Kīlauea's flank in at least 2200 years.’ Mauna Ulu’s record has since been shattered by the ongoing Pu‘u ‘Ō‘ō eruption, which has persisted for over 35 years in a continuous eruption that started January 3, 1983. The eruption sent lava flows oozing into ‘Alae Crater, and even once into the ocean 12 km (7.5 mi) away. In one crater, a massive lava lake formed. At one point, the lava cascades pouring down the sides of ‘Alae were ‘higher and wider than American Falls at Niagara,’ according to USGS. Over the course of two years, lava from the eruption build up a massive ‘shield’ that stood 80 meters tall by July 1970. From October 15, 1971-February 3, 1972, the eruption went ‘into hibernation.’ But, it resumed that winter to reform a shield even larger than the previous. Between the end of 1973 and summer of 1974, the activity began to die down. Short-lived fountains sprung up, with intermittent overflows. Eventually, the lava lake dwindled. On July 22, the eruption was officially declared over. The Mauna Ulu eruption was a 5-year-long event at Hawaii’s Kīlauea volcano that lasted from May 24, 1969 until July 22, 1974. On left, lava pouring from one pit to another in the Pauahi Crater, November 11, 1973 is pictured. Advertisement

While the fountaining episode that created the dome lasted just about three days, the eruption itself was far longer.

It began months earlier, on May 24, 1969, and lasted until July 22, 1974.

‘At the time,’ USGS says, ‘it was the longest-lasting and most voluminous eruption on Kīlauea's flank in at least 2200 years.’

Mauna Ulu’s record has since been shattered by the ongoing Pu‘u ‘Ō‘ō eruption, which has persisted for over 35 years in a continuous eruption that started January 3, 1983