2017-02-03 20:27:10
Trilobites: Streaming Lava, Collapsing Cliffs and a Hawaii Volcano’s Spectacular Show

20:27, February 03 571 0

Off the coast of the island of Hawaii, hundreds of millions of gallons of lava are flowing into the ocean like blood from a ruptured artery. Starting in January at Kīlauea Volcano’s Kamokuna ocean entry, the lava hit the salty water, shooting molten rock upward and outward, accompanied by a rising, steamy cloud of acid.

Normally cooling lava would stack up, creating a rocky shelf on which the lava settles called a lava delta. But this time, the flow continued to gush nearly 100 feet down, into the sea, for a whole month.

This same volcano has sent lava traveling through tubes from moving vents along its East Rift Zone known as Pu‘u ‘Ō‘ō, ever since it erupted 34 years ago. And these tubes have carried it to a number of spots along the ocean. But streams like this usually only last a day or two. This one lasted from New Year’s Eve, when 21 acres of lava delta collapsed into the ocean, exposing the tube, until Thursday, when an unstable seacliff collapsed and finally cut off the picturesque stream.

On Wednesday the USGS Hawaiian Volcano Observatory noted that the sea cliff just near the entry was becoming increasingly unstable, and could collapse at any moment. By 6 p.m. E.T. Thursday, a crack in the seacliff split open and it fell into the sea. Lava is still flowing into the ocean, said Janet Babb, a geologist at the observatory, who monitors the volcano, in an email Thursday night. But she was uncertain that the fire hose flow was still visible.

“As I like to say, the only constant on this volcano is change,” Ms. Babb said.

Photos and videos of this spectacular lava flow into the ocean spread on social media this week. Flowing from Kilauea at a rate of about one or two cubic meters a second, somewhere between 788 million gallons and 1.576 billion gallons of lava flowed from Kilauea Volcano into the ocean during the firehose’s monthlong show.

Why did this lava fire hose last so long?

“The only thing we can surmise is the offshore topography apparently is so steep that, as the lava is flowing in and forming all this new rubble, it’s just slipping down into deeper parts of the ocean and not piling up to form a new delta,” Ms. Babb said ahead of the cliff collapse on Thursday. “Lava will continue to flow into the ocean until it’s disrupted.”

The geological events that led up to the fire hose started long before the new year.

In May 2016, a new vent broke out on Pu‘u ‘Ō‘ō. Lava started flowing and moving south toward the coast. As the lava moved, the part touching the air cooled and crusted over, resulting in lava tubes that made its passage to the ocean far more efficient, as veins channel blood. The tubes from this volcano range in diameter: from so fat that a bus could pass through to so skinny that a human couldn’t.

The lava traveled seven miles down these tubes, and by July 26, 2016, the lava had reached the ocean. At the time, that was big news, said Ms. Babb, because that was the first ocean entry since 2013.

When hot lava hits salty water it results in a chemical explosion. Rubble forms, stacks up, and lava mounds up over it creating a lava delta. Over four months between July and December, this lava built a 24-acre delta.

“Lava deltas are inherently unstable because they’re built on a foundation of rubble,” said Ms. Babb. They noticed cracks developing in the delta.

“On New Year’s Eve the inevitable happened. The lava delta collapsed,” she said. Four acres of seacliff beside the delta and near an area that can get thousands of daily visitors also crumbled into the ocean below.

When park rangers saw what was happening, they moved the viewing area farther away and actually had to turn people back who had ventured into the closed area minutes before the collapse.

“The greatest feeling was a gratitude that no one was injured or killed during the collapse,” said Ms. Babb.

The fire hose of lava was beautiful, and dangerous. When the 2,100 degree Fahrenheit lava hits 70 degree salt water, it results in an explosive reaction that sends rock, glass and fragments of molten lava called spatter onto the land and out to the sea, where it endangers wildlife, hikers and tour boats. Dangerous waves form and the heat alone can boil fish that can’t escape it alive.

“That big white steam plume looks rather harmless, but it’s a superheated steam laced with hydrochloric acid,” she said, and a delta collapse magnifies the danger.

Park rangers determine safe viewing areas for patrons with observations carried out by the team at the observatory, but safety isn’t guaranteed. Those interested in viewing the flow in person can follow the observatory’s daily eruption updates and photos, or check out the park’s website and remain cautious.