Thread by @SquigglyVolcano

So...the eruption of Nyiragongo on Saturday may have been short-lived, but as the heightened seismic activity in the region and the evacuation order for part of the city of Goma makes clear, something's still happening. But what?

A short thread... france24.com/en/africa/2021…

First off: it's important to remember that I'm a science journalist. I trained as a volcanologist, but my job is to report on things like volcanic activity by talking to scientists and write up stories based on that. I'm one step removed from the real-time events. 2/x

My @NatGeo story on the short-lived but nevertheless destructive and deadly eruption of Nyiragongo this past weekend can be read here. It also explains why the volcano is so dangerous, and why it came as a surprise even as it was being monitored. 3/x nationalgeographic.com/science/articl…

Another key thing to note: be careful what you share on social media. Misinformation is spread both willingly and accidentally during a volcanic crisis. If it's not from a trusted journalistic outlet, a reputable science journalist, or scientists themselves, be skeptical. 4/x

One last thing: I've been told that the Goma Volcano Observatory isn't allowed to speak with the media during a crisis; only the authorities can do that. Cutting off lines of communication between journalists and scientists is never a good idea, but hey, those are the breaks. 5/x

So, with all that in mind...what the heck is going on with Nyiragongo right now? With major caveats, let me try to explain. 6/x

This weekend's eruption ended as abruptly as it began. Lava poured out of fissures in the volcano, they sped toward Goma but they didn't quite make it. They did, however, plough through several villages, killing dozens and destroying hundreds of homes. 7/x

Satellite imagery taken soon after the eruption appeared to show that the persistent lava lake within Nyiragongo's summit had been drained as a result of the eruption. Some of this drainage was likely out of the volcano, creating those lava flows. 8/x

https://twitter.com/CultureVolcan/status/1397430137948459008

No two volcanoes are the same. Saying that, the lava lake at the summit of Hawai'i's Kīlauea volcano drained rather dramatically back in May 2018, and in this case the magma snuck under the volcano and headed to its eastern flanks, where it erupted. 9/x nytimes.com/2018/12/12/sci…

The region around Nyiragongo has been rocked by not-insignificant earthquakes in the past few days. This is not a coincidence. 10/x

It's difficult to know what the seismic activity represents though. This is the first time than an expansive network of seismometers have been operational during a Nyiragongo eruption, so scientists can't immediately understand what the seismic rumblings represent. 11/x

But whenever an eruption takes place, magma moves underground. Magma pushing rock aside makes quakes, but the relaxation of the crust, closing up a little around a newly-made magmatic vacuum, causes quakes too. The GVO explain here: actualite.cd/2021/05/26/gom…

Scientists have also been using satellite-based radar systems to see how the ground has changed shape, which can be used to try and infer where any magma has moved too. And, well... 13/x

https://twitter.com/EricFielding/status/1397332539048488960

I must stress that at present, this work is preliminary. I am making no interpretations myself, and none of this is official -- I'm just trying to fill in a bit of a vacuum on social media that is getting a lot of speculation instead of factual information. 14/x

Anyway, studies in the past have been wary of magma moving elsewhere in the region. This 2018 report, part-authored by members of the GVO, warns that the volcano's fracture network "from Nyiragongo summit to Goma and continues beneath Lake Kivu..." 15/x

And that, it notes, "gives rise to the fear that an eruption could even produce an active vent within the center of Goma or within the lake."

This is a possibility, but not a certainty. Do note that. 16/x

In certain situations, when magma reaches water and mixes with it, it can produce explosions, a type of activity known as phreatomagmatic. Recent papers have shown that several have happened in the not-too-distant geologic - historical, even - past. 17/x link.springer.com/article/10.100…

In other words, magma erupting from underground into Lake Kivu isn't what anyone wants, especially along its urbanized northern shoreline. But it *has* happened before. 18/x

General Constant Ndima, the local military governor, said this today: "Right now we can't rule out an eruption on land or under the lake (Kivu), which could happen very soon and without warning." 19/x france24.com/en/africa/2021…

There are two risks here: Lake Kivu has a lot of carbon dioxide and methane in it which, if destabilised by volcanic violence, could pool onto its shores. These gases are toxic; carbon dioxide seepage from aquifers into low-lying areas kills people here every single year. 20/x

The other risk is the explosive interaction of magma and water, which is difficult to predict. 21/x

And why is there such concern right now? "Current data on seismicity and the deformation of the ground indicate the presence of magma under the urban area of Goma, with an extension under Lake Kivu,"said Ndima in a broadcasted public address. 22/x

That is why, thankfully, authorities have ordered the evacuation of part of the at-risk population in Goma. This magma may do nothing; it may cool down and not erupt. But the risks of an eruption are too high to do nothing, hence today's evacuation order. 23/x

And now, we wait. Thanks again to all the scientists at the GVO and their international partners for working around the clock to quite literally save lives. Let's hope that this crisis at the very least results in the GVO getting the funding it actually deserves.

End.