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On December 18th, 2023, near the town of Grindavík, Iceland, a four-kilometer-long fissure opened and spewed lava skyward, in a beautiful and terrifying show of nature’s power. Several more eruptions have followed, and more might even occur between the time we’re filming this and the time you’re watching it.

Magma continues to accumulate beneath the ground, and it seems like we’re going to see quite a few more eruptions before everything calms down. We know this because scientists in Iceland have a toolbox of ways to closely monitor and forecast volcanic eruptions. But, they’ve faced some challenges.

While there’s never a good time for a volcano to erupt, it turns out winter in Iceland is especially bad. That’s because it’s tough to monitor a volcano in stormy, dark, wintry conditions. And no, it’s not just because geologists don’t like being cold. [SciShow Intro] Now, remember that not all volcanic eruptions are your classic cone-shaped mountain blowing its top.

This is more a bunch of cracks opening up from below, and not just in one place either! No matter what kind, though, predicting an eruption is tough under the best of circumstances, and an Icelandic winter is not the best of circumstances.

Shawn: yeah, in general, the weather in Iceland is often not very amenable to volcanic monitoring. Oh, by the way, we decided to ask an expert to help us understand why it being winter has anything to do with monitoring a volcano.

Shawn: My name is Shawn Willsey. I am a geology professor at the College of Southern Idaho in Twin Falls, Idaho. Shawn has been livestreaming these eruptions, which is a thing you can do in this century, as well as creating a bunch of informative content on YouTube that we’ll link in the description. So, what do stormy North Atlantic winters have to do with molten rock coming out of the ground?

Well a few things, actually. Seismographs are used to monitor the swarms of small earthquakes that often come before an eruption. But these instruments pick up all kinds of vibrations.

Shawn: the wind can also affect our ability to detect very small earthquakes with some of the seismometers. If it’s stormy with a lot of wind, or pounding waves near the shore, seismometers are so sensitive – and some of these earthquakes are so small – that the weather actually obscures the presence of earthquakes. Scientists also use GPS sensors to track how the ground rises when magma accumulates beneath it. But heavy precipitation can interfere with a GPS antenna communicating with satellites, which creates gaps in the data.

Luckily, volcanologists have another way of measuring how the ground deforms. InSAR is a method that uses a satellite to bounce pulses of radar off the ground. Making multiple passes over the same spot and comparing the bounced signals can tell you how the ground is deforming.

InSAR is pretty good at seeing through clouds from winter storms, but it has an Achilles heel: snow.

Shawn: So, InSAR uses radar. And so if you have, we're trying to measure changes in the, the land surface, but if you do a pass with the satellite and measure the elevations and then it snows three inches and then you do another pass, now the land is risen because of the snow, but not because of uplift. In fact, InSAR can be used to measure and monitor snow levels in super remote places, but let’s just say ski conditions in Grindavík aren’t the priority right now. Finally, scientists can also learn a lot from analyzing the amount and composition of volcanic gases.

Collecting these samples by hand comes with all the risks associated with walking into an active volcano. Tragically, in 1990, six scientists were killed when sampling gas from a volcano in Colombia. Fortunately, now we can monitor those gases remotely, at much less risk to human life.

The technique is called Differential Optical Absorption Spectroscopy or DOAS. See, as a beam of ultraviolet light shines through the air, the gases it passes through absorb certain wavelengths of the light. This means each gas creates a unique fingerprint in the light that travels through it.

You can see the gaps where something’s missing, almost like a shadow. So you can set up a sensor and look at the spectrum of light that just traveled through a volcanic plume. By comparing this to light that only traveled through the atmosphere you can see which wavelengths of light are missing and figure out how much of a particular gas is in that plume.

A DOAS sensor can measure gases as accurately as a part per trillion. Just by looking at the light that passes through it! Now, you do sort of have to play around with angles a little bit for this to work.

Shawn: the spectroscopy requires that you can see through the gas plume. And if your volcano's at the top of a, a mountain, like a cone shaped volcano, then it works pretty well. But if your volcanic vent or your volcanic region is in a low area, like in a valley, then you don't have a clear line of sight through that volcanic gas plume, with sunlight behind it.] This technology has been around since the 1970s. But it wasn’t until the 2010s that we’ve been able to make them portable enough to allow scientists to quickly set them up in hard to reach areas, which is often where you find erupting volcanoes.

The most common gas present in a volcanic plume is water vapor, followed by carbon dioxide. But these are both pretty common in the atmosphere naturally. Because volcanoes only increase the amount of these gasses by a little bit, that’s tough to measure.

It has been done, but you need a really wet volcano in a really dry place to be able to measure water vapor with DOAS. So most often these sensors look for sulfur dioxide. An increase in sulfur dioxide emissions means that magma is coming up to the surface, so it’s a good indicator for forecasting an eruption.

Not that it’s foolproof though. A 2011 eruption in Nicaragua had a pretty slight increase in sulfur dioxide right before. But after the fact, researchers pointed out it ended up being a relatively small eruption that didn’t involve a big shift in magma.

Iceland has a number of volcanoes that are constantly watched by DOAS sensors, part of a global monitoring network. They installed two new portable instruments in November 2023 when it looked like things around Grindavík were heating up. This came along with a disclaimer from the Icelandic Meteorological Office that using them would be challenging.

Remember, you need a source of ultraviolet light. The Sun works perfectly, when it’s around.

Shawn: we’re not able to use the sunlight To measure the volcanic gases because we have this short window of time. Uh, and so it's real limiting at places like Iceland where it's just, it's just not feasible this time of year. We checked and Reykjavík gets a solid four hours of daylight on the winter solstice. Less UV light means the sensor receives a lower signal, and the measurements it makes aren’t as accurate.

Now, scientists have found some clever ways around this. Some have successfully used the light of the Moon to make measurements at night. Using the natural light of either the Sun or Moon is called passive DOAS.

The other way to do it is to bring your own light, that’s called active DOAS. This means setting up a spotlight next to your sensor and a mirror on the opposite side of the plume, reflecting artificial light through the volcanic gas. It means more things to set up and get electricity to, but it does help you see a volcanic plume in the dark.

Now, this might make it seem like we’re trapped between two sources of nature’s wrath – between an erupting volcano and a ferocious winter. That doesn’t mean we can’t do anything. On the contrary, we have an astonishing amount of information about this ongoing event.

Remember how I told you Shawn livestreams these things? There’s webcams! Seriously!

Shawn: And that's what's, um, that's what's amazing about volcano monitoring is our first real excellent piece of data once the eruption has begun is just observation based. And so it's looking at webcams, it's maybe boots on the ground people that are there. It could be drones, but that information is incredibly valuable. And not just understanding the eruptive behavior of that specific episode, but possibly predicting how that eruption's going to evolve over time.

Direct observations from whether it’s scientists Or just general public viewers Is an incredibly important part Of the volcano monitoring game Thanks to Shawn for sharing all of his incites Again you can find links to his work In the desription Never underestimate the combination of plain ol’ human eyeballs and scientific curiosity. We’re getting better at predicting volcanic eruptions – and keeping people safe – every day. If they do decide to evacuate the area, it would be a bad time to own rental property out there.

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