Too many people around that The almost certain prospect of a new volcanic eruption on the Icelandic peninsula of Reykjanes sounded threatening to the world. But in March 2021, when lava poured from a crevice in a valley called Geldingadalur – a comfortable six miles from the nearest town, Grindavík – those in Iceland were nothing but delighted.
The public was thrilled to see an outbreak up close – one that was not very dangerous. Drone pilots flew their devices like X-wing pilots over rivers of molten rock. Scientists began forensically investigating this once-in-a-millennium event, which gives them a glimpse into the part of the land that is literally being torn apart by titanic tectonic forces.
It’s the best scenario for an outbreak anywhere. Everyone is a winner. And because the volcano known as Fagradalsfjall looks very much like a school science project, this constantly documented eruption is a great opportunity to explain some of the basic features of this type of magmatic miniature mountain.
Drone shots allow a view into the spray cone.
If you take a look at the live webcam footage of the outbreak, you will be greeted with an amazing sight. On the night of March 19, the meandering curtain of lava seeping from a 1,650 foot crack in the earth became a much more focused matter. Molten stone began to gurgle and jumped out of some kind of broken cauldron. At night, the Basilica of Fire is lit by its own radiant streams as it gives the Lava Valley a long overdue fresh coat of Hadean paint.
The high structure is called a spray cone. As is common with crack eruptions, the magma underneath finds a path with the least resistance and begins to bubble onto the surface. The lava that spreads around it begins to cool and solidify and forms a kind of ring. Lumps of lava – that’s the splash – splash over time onto the ring of rock, eventually forming a cone that looks like a funny volcano.
Spray cones can sometimes reach impressive heights quickly. During the 2018 eruption sequence at the Kīlauea Volcano in Hawaii, a cone at fissure eight (out of two dozen) grew to 180 feet tall. The cone and the gap have since been named Ahuʻailāʻau after the altar of a volcanic deity. If this Icelandic cone survives its own breakout, it might get a name too.
Due to the nature of the lava in Fagradalsfjall, the risk of explosive events is low.
Splash cone construction can be messy and arbitrary, and this baby cone in Iceland is no exception. On March 21, one side of the cone collapsed, causing a small lava cascade to run over the valley. At the time of going to press, the cone had lava from two separate outlets, technically known as vents.
This lava is sometimes in the form of streams in which the lava cools slowly and flows smoothly, which is called pāhoehoe (thank you, Hawaiʻi!). As the lava continues to move, but clumps up a little and cools faster, it tears itself apart, forming cloudy, jagged, thicker streams that scientists call “a”.
The surface of the lava cools quickly on contact with air and forms the characteristic black crust. However, here and there you can see tiny red spots. These are skylights, windows in the still-melted rock directly below. When this unstable rocky roof collapses, lava puddles can sometimes spread out irregularly.
The color of the lava under the solid crust is an indication of its heat.
Whatever it is, this lava is hot. Very hot. You don’t need an infrared camera to see this. And its color is an indication of that heat – from scarlet to clementine, which is roughly 1,450 to 1,850 degrees Fahrenheit. It’s way too hot to grill properly; Any food you put on it will go up in flames or will be crushed before melting. It is best to wait for the lava to cool to a rock that, while still hot, is not a bad way to grill sausages if you are extremely careful.
This eruption temperature is typical of that flavor of lava known as basalt, and this species explains a lot about the type of eruption we see. Magmas (lava when it’s still underground) often contain a decent amount of silica, molecules that are made into a kind of skeleton by the hellish soup that holds them together, much like the proteins in an egg white. Lavas with relatively high concentrations of silica are thicker and more custard-like. Once they have dissolved a lot of gases deep underground, they can suddenly expand violently as the magma breaks through to the surface and creates explosions.
But basalt doesn’t have that much silica, so it’s much more runny, warm honey than pudding. As a result, its gases tend to blow out fairly calmly. So unless it mixes with ice or a shallow body of water that can trigger steam-powered explosions and produce a lot of ash, large booms are much less likely.
Although the lava at Fagradalsfjall is liquid, it is easy to avoid and therefore accessible.
Instead, from time to time you may see fountains of lava, vertical streaks of molten rock pushed up into the sky by a cluster of bubbles underneath, as if popping the cork on a shaken bottle of champagne. Gas bubbles previously trapped by pressure escape into a low pressure environment, and when they flow outside they bring the delicious champagne or the less delicious lava with them.
The earlier stages of the Fagradalsfjall eruption were a bit more gaseous and had more momentum, so there were a number of small lava fountains. The ongoing eruption of Mount Etna in Sicily has definitely put it down in this department. It once blasted its own basaltic lava into the clouds, with individual wells being more than twice as high as the world’s tallest skyscraper.
If you don’t want to know what it feels like to be flamed or hit by an overheated, refrigerator-sized cannonball, standing next to the spectacular peak eruption of this Italian mountain would be an all-round terrible thing to do. But the adorable fit at Fagradalsfjall is so self-contained that the public – originally advised by authorities to stay away but now named the best place to stand – can simply roll onto a nearby ridge and watch the youngest land on earth before their eyes forged.
When you are uphill from the lava this is some level of security.
It’s not a risk-free activity. It is possible that another eruption could occur suddenly along another fissure in the area and like the original crevasse opening doesn’t provide much warning. The gas cloud that emerges from the ventilation slots can also be problematic. Much of it is water vapor, but there is also sulfur dioxide, a gas that, even in small amounts, can dangerously worsen the lungs of people with respiratory diseases such as asthma.
Overall, this eruption is relatively safe and accessible as most people can easily overtake basaltic lava even with a flowing type of magma on a flat surface. When you sit uphill, you put a natural barrier between you and fiery fate. At the moment, the greatest danger is not in the fire, but in the ice. Some spectators parked their cars and then stayed until dark – and then got lost in a blizzard while trying to leave.
Nobody is sure how long this outbreak will last. However, the dimensions of the magma ribbon it fires have been estimated based on changes in the soil in the region over the past month. It’s pretty thin and about four miles long. Assuming a modest amount of magma erupts in its entirety, the eruption could take a few more weeks.
The eruption could be short-lived or a harbinger of centuries of volcanic activity on the Reykjanes Peninsula.
But if more magma comes from deep below, it could continue like this for these months or even years. At the current rate of production, it is entirely possible that the lava will eventually fill the valley. There is no need to worry as this valley is surrounded by other valleys like this one. It would take a long, long time, and it would take a lot of lava to become a threat to cities or people on the peninsula.
However, there is a good chance that this outbreak will mark the beginning of many decades or even several centuries of eruptions across the peninsula, as has happened at least three times in the past millennia. That this will take place on a sparsely populated strip of land is an ideal volcanic situation you will get.
Like this youthful eruption we are all wondering about, a new era of widespread volcanic pyrotechnics on the Reykjanes Peninsula is something anyone can enjoy. Not only will it reveal more to scientists about the enigmatic, magmatic engines that power this ever-changing land, but viewers both in Iceland and elsewhere in the world will gain a new appreciation for this dynamic, beautiful world: a light blue dot sprinkled with fire.