Thread by @SquigglyVolcano

NEW: This weekend's eruption could have been worse, but it doesn't change the fact that Nyiragongo remains one of Africa's most dangerous volcanoes—partly because of its exotic lava, partly because of complex sociological factors.

Me for @NatGeo + thread! nationalgeographic.com/science/articl…

The oddly small eruption this weekend didn't reach the populous city of Goma, in the DRC. But it hit 17 villages, cut off water and electricity supplies, took out a school and destroyed hundreds of homes. 15 people have been confirmed dead at the time of writing.

1/x

This also happened, lest we forget, during a pandemic. Thousands fled across the border to Rwanda, and the majority of those deaths happened during an evacuation-based traffic accident. Things were pretty chaotic.

2/x

Nyiragongo is a seriously dangerous volcano. In 1997, many hundreds were killed by lava flows; in 2002, 100-300 died when through burns, suffocation from noxious volcanic fumes, and when lava caused a gas station to explode. Hundreds of thousands were made homeelss.

3/x

That the city - and the city of Gisenyi just over the border in Rwanda - is right next to the volcano makes any eruption a problem. But it's the geologic forces that made Nyiragongo in the first place that also make it so dangerous.

4/x

Thanks to the East African Rift - a strip of land from the Red Sea to Mozambique that's slowly being pulled apart by tectonic forces - and thanks to the rise of a deep-seated plume from the underlying mantle, volcanoes here often have weird magma chemistries.

5/x

Most magma has a decent amount of silica in it, a compound that acts as a sort of skeleton in molten rock. The less silica you have, the less viscous or goopy the lava is once it erupts.

6/x

Basaltic magma, the stuff erupting out of Iceland’s Reykjanes Peninsula right now, has a low proportion of silica in it, making it fairly runny, but on a flat surface it can easily be outwalked.

7/x

Not so for Nyiragongo’s molten matter: Its lava has such a deficit of silica that it zips across the ground, sometimes at speeds of 40 miles per hour. That's impossible to outrun.

8/x

The magma also exudes a lot of carbon dioxide to the surface, both during and outside of eruptions. It gathers in low-lying areas, and being invisible and odorless, it does so silently. Every year, people asphyxiate in these pockets across the region.

9/x

Nyiragongo has had the Goma Volcano Observatory since 1986. But this eruption is the first time a fully-fledged network of monitoring equipment has been operational during an eruption. Even then, there were no clear warning signs than an eruption was incoming.

10/x

The World Bank cut its funding to the observatory last year, and seismic stations have always been at risk of theft or vandalism. But a trickle of state funding and international partnerships allowed the observatory to do a some monitoring here and there...

11/x

...and yet this eruption came as a surprise to everyone. The volcano is still shaking and quaking, so something is still going on, but it's not clear what.

It could have been so much worse. The next eruption might be. Only time will tell.

End.

Thanks to @smetsbenoit, @seis_matters, @CoCaudron and @MatthieuKervyn for chatting to me at such short notice; sorry we couldn't quite chat this time, @kaylai. And I tried (as ever) to speak with volcanologists on the ground there, but none (understandably) got back to me.

And thanks as ever to @jaywbennett and @vmjaggard99 for hearing my "yet ANOTHER volcano has erupted on a weekend" email cries. :p

Hey @jessphoenix2018, have you ever been to Nyiragongo?