BREAKING: The Hawaiian volcano Mauna Loa has begun erupting, with lava currently confined to the summit. It’s the first eruption at the volcano since 1984.
This situation could evolve in a number of ways.
Thread! 🧵
This situation could evolve in a number of ways.
Thread! 🧵
https://twitter.com/usgsvolcanoes/status/1597165287899811840
There's a lot going on here, and a lot that could or could not happen, but first and foremost, follow @USGSVolcanoes for official updates. As usual, I'm hoping to write up a @NatGeo explainer on the sitch, but my editor is (understandably) not awake yet. Standby!
Okay, so:
Okay, so:
First off: no, this has nothing to any other eruption happening anywhere else in the world at the same time. No, this eruption doesn't imply some sort of apocalyptic tsunami/earthquake is about to happen. Anyone saying anything of the sort is talking out of their arse.
The significance of Mauna Loa erupting comes from a variety of historical reasons, but the fact that it is a hazardous mountain that hasn’t erupted since 1984 – the longest eruptive pause in its recorded history – is why we should all keep an eye on it.
Mauna Loa is a rather massive shield volcano on the Island of Hawaii—“shield” in that it is a lot wider than it is tall, but it’s still about 2.6 miles tall, so yeah, it’s a big volcano.
In fact, it’s the largest active volcano in the world: much of it is submerged beneath the waves, meaning that its summit is actually about 10.5 miles off the seafloor. Mauna Loa is spread over an area equal to about 2,000 square miles, so yeah, it’s gigantic.
Its name means “Long Mountain”, in fact.
Like all the volcanoes in the Hawaiian archipelago, this is a hotspot volcano: deep beneath the Pacific tectonic plate, a superheated fountain of matter – a plume – has been rising from considerable depths over epochal time through the solid-but-squishy mantle.
As the plume reaches the underbelly of the Pacific plate (which is a lithic biscuit made of the upper mantle with the crust overlain atop), its heat melts its surroundings, creating magma.
The material shuttled up within the plume itself, when encountering these lower pressure environs, also melts, creating more magma.
The mantle plume beneath the Pacific plate hasn’t moved for an age, but the tectonic plate itself has been drifting all over the place; that means that this plume has been hitting a moving target, ultimately leading to the creation of many volcanoes in the archipelago.
Mauna Loa is just one such volcano; it happens to be the most colossal of them all.
The plume isn’t directly beneath it anymore, but it is most certainly “active”–a volcanological shorthand that means the volcano has erupted once in the last 12,000 years or so, which implies it can erupt again.
And indeed it has.
And indeed it has.
This volcano, situated sort of in the middle of the Island of Hawaii, has not been one to let Kīlauea, its cousin to the southeast, have all the fun.
(Incidentally, I’ve covered Kīlauea a *lot*, including a recent retrospective on it for the @nytimes and for a whole chapter of my popsci book, SUPER VOLCANOES. It’s a fairly different volcano to Mauna Loa, just FYI. nytimes.com/2021/11/09/sci…)
Mauna Loa has erupted 33 times since 1843, an approximate cadence of one eruption every five years.
Both extensive geological evidence (old, frozen lava flows) and the oral histories of Native Hawaiians (whose ancestors first settled on the archipelago around 1,600 years ago) demonstrates that there were many, many eruptions long before this...
...but 1843 is roughly when solid written records of the volcano’s activity began.
However, as the USGS note: “most eruptions occurred prior to 1950, averaging 3.5 years between eruptions...
However, as the USGS note: “most eruptions occurred prior to 1950, averaging 3.5 years between eruptions...
"Since 1950, there have only been two eruptions; a summit eruption 25 years later in 1975 and by a rift eruption 9 years later in 1984. As of 2022, it has been 38 years since the last eruption, the longest quiet period on record.” usgs.gov/volcanoes/maun….
The volcano erupts a particularly fluid, hot lava that turns into a rock named basalt.
It’s broadly the same chemistry as the stuff that exsanguinates from Kīlauea: it often initially oozes out at 1,800 degrees F (1,000 degrees C), and likes to form its own channels, subterranean lava tubes, “lava”falls and so on.
It is not the sort of chemistry that usually leads to "explosive" eruptions: ones with big columns of ash, pyroclastic density currents and so on. Eruptions at Mauna Loa are effusive, meaning oozing lava for the most part.
Like Kīlauea, Mauna Loa’s lava erupts from two sorts of places: the summit, or peripheral vents/cones and/or fissures on flanks along rift zones.
Rift zones are parts of the volcano that are being gradually torn apart by local tectonic forces and the underlying migration of magma; when wounds open in these rift zones, eruptible magma beneath them may erupt out.
Geological evidence shows that, since the year 1200, new eruptions have occurred mostly from vents/fissures along rift zones. Prior to that, lava erupted mostly from the summit before sometimes overflowing the summit crater. 
Per the USGS, lava flows switched from the summit to the flanks around 1200 because the summit collapsed in on itself around that time; this created a deep bowl, or “caldera”, that meant that although lava bubbled from the summit, it was largely confined within the caldera.
The locations of new rifts opening on the flanks of volcanoes are hard to forecast; although the movement of magma can be tracked by the seismic symphony they make as they crack the crust, the timing of when a fissure may open, and its exact location, can be vague.
As of 1am Hawaiian time (that’s 6am eastern time), there is no evidence that magma is moving toward any rift zone on Mauna Loa’s flank. So far, the lava is contained to the summit.
But that doesn’t mean everything’s fine.
But that doesn’t mean everything’s fine.
Eruptions at Mauna Loa frequently involve lava pouring downslope, sometimes into populated neighborhoods.
So what can Mauna Loa’s most recent eruptions tell us about the potential paths this new eruption may take?
So what can Mauna Loa’s most recent eruptions tell us about the potential paths this new eruption may take?
Important caveat: past eruptions only offer a guide to the myriad ways in which a new eruption may evolve. They are not forecasts or guarantees, as every new eruption is unique in many ways.
Eruptions at Mauna Loa, and the associated hazard with the lava, largely depends on which way the lava tends to go after it begins erupting.
The 1859 eruption created a 32-mile (!) flow over the course of 300 days, the most voluminous eruption since Europeans “arrived” on the archipelago. On steep slopes, the lava flowed up to 10 miles per hour.
This eruption destroyed various islandic resources, including key fishponds, part of a coastal community’s living space, and a sheltered bay.
In 1881, another eruption took place, but this one began at the summit.
In 1881, another eruption took place, but this one began at the summit.
There was a multi-month pause before the eruption got going again from vents on a northeast rift zone. This lava flow was advancing toward the town of Hilo, and villagers put up barricades to try and stop it (in vain)
As I note in my @NatGeo article: “Princess Ruth Keʻelikōlani—the descendant of Kamehameha I, the founder of the Kingdom of Hawaii—arrived at the scene to pray to the volcano goddess Pele and provide material offerings, including brandy and scarfs.
The lava flow did stop shortly afterward, but had it not been stanched by the princess’s pleas, local authorities were prepared to set off an explosion at the front of the lava stream with a hefty supply of gunpowder.”
Another eruption, in 1935, threatened Hilo again, and it was decided that the lava flow should be redirected through use of high explosives—bombs dropped by military aircraft.
Turns out that this didn’t work, and in fact the use of explosives to divert lava flows is almost always a bad idea. It’s only worked once, on the slopes of Etna in Italy. nationalgeographic.com/science/articl…
The last Mauna Loa eruption was in 1984, involving both summit and flank eruptive activity. What began as lava fountaining up and into the summit led into the opening of several flank fissures.
Soon, the eruptive activity focused on one section of the volcano’s slopes, wherein multiple cones were built by lava shooting out of a nested collection of fissures. Various sites were eventually threatened, including a prison at once point.
The increasingly populous city of Hilo was, once again, in danger—but, luckily, for the nth time, the magma supply dropped off just in time to spare it.
Hilo isn’t the only city/town/neighborhood that Mauna Loa’s lava flows can endanger, but it does frequently find itself in the way.
So, as you can see, eruptions vary in style, volume, location, and duration considerably.
So, as you can see, eruptions vary in style, volume, location, and duration considerably.
Mauna Loa is a very difficult beast to study; despite having plenty of information on past eruptions, foreseeing the future is difficult. And their potential hazards aren’t just confined to red-hot lava flows.
If lava enters the sea or into a large lake, it can create plumes of “laze” (a portmanteau of lava and haze) which is a mixture of hydrochloric acid, steam and fine glass particles; this is largely not a problem for those with healthy respiratory systems, but it has been known…
…to kill people right next to the plumes in the past. Fortunately, people are kept far from areas in which laze may appear.
Vog, (volcanic fog) is a similar-ish hazard that’s created by volcanic emissions coming from the volcano itself: water vapour, carbon dioxide and sulfur dioxide, a potentially irritating admixture that can also reduce visibility.
Plumes of ash that may emerge from the summit during any minor explosive events (trapped gassy magma popping a rocky cap, or mixing with groundwater, say) can be dangerous for aircraft, but none will be allowed to fly over the summit unless part of an official scientific mission.
Fortunately, Mauna Loa is one of the most well-monitored volcanoes on the planet. Monitoring efforts have only shot up since the paradigm-shifting 2018 eruption at Kīlauea, itself the “culmination” of decades of continuous activity at this volcano.
In fact, prior to the 2018 conflagration at Kīlauea, the Hawaiian Volcano Observatory was largely concerned about the next eruption of Mauna Loa.
Mauna Loa, as of the past year or so, had been twitching to a somewhat concerning degree.
Mauna Loa, as of the past year or so, had been twitching to a somewhat concerning degree.
As an active volcano, it isn’t unusual to have it change shape and quake here and there, but the deformation and the frequency of quakes – likely caused by the movement of magma – had become significant enough that an eruption was looking a little more likely than before.
“Hawaii's civil defense agency is holding meetings...to educate residents about how to prepare for a possible emergency. They recommend having a ″go″ bag with food, identifying a place to stay once they leave home and making a plan for reuniting with family members.”
That was CBS News not too long ago: cbsnews.com/news/hawaii-vo…
And now, a new eruption has begun.
So far, it’s contained to the summit, and there is no evidence of any flank eruption on its way.
So far, it’s contained to the summit, and there is no evidence of any flank eruption on its way.
https://twitter.com/USGSVolcanoes/status/1597166066496851968
No evacuations are being called at this time. The two major rift zones of the volcano are showing no worrying signs of anything at all at present.
https://twitter.com/USGSVolcanoes/status/1597167709170827264
The warning code for the eruption – RED/WARNING – may confuse some.
The colour refers to the aviation warning (RED = eruption may make plenty of ash, so planes must stay far away); the 2nd word refers to the danger posed to those on the ground (WARNING = a hazardous eruption is imminent, underway or suspected). usgs.gov/observatories/…
What’s next? I don’t know, of course, and neither does anyone. The Hawaiian Volcano Observatory is on the case. Everyone on the island is on the highest alert.
This eruption could be confined to the summit and that’s it. Or something more dangerous may happen. It could peter out today, or last for weeks or months. We’ll just have to see.
https://twitter.com/USGSVolcanoes/status/1597170103489290240
End of thread, for now. Follow @USGSVolcanoes for official updates; ignore all soothsayers from now until the end of time. I'll share important updates on the eruption when they appear.
cc @jaywbennett
No soundcloud, but I do have a (critically acclaimed!) popsci book on volcanoes and volcanologists y’all might like! :)
https://twitter.com/SquigglyVolcano/status/1592542057155133441
Just to note that this has been viewed nearly a million times already—and getting accurate info on evolving crises out there as fast as possible is one of the best uses of Twitter. Hope I get to continue doing this under the new, um, regime for as long as I can.
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