Iceland’s volcano finally erupts: A geologist explains what’s happening

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Lava erupted via a fissure in Iceland’s Reykjanes Peninsula on Dec. 18, 2023, capturing almost 100 feet (30 meters) within the air in its early hours.

Icelanders had been anticipating an eruption within the space for weeks, ever since a swarm of thousands of small earthquakes started on Oct. 23 northeast of the fishing city of Grindavík, signaling volcanic exercise beneath.

Within the days that adopted these first rumblings, a collection of small rifts opened beneath the city, breaking streets, rupturing utility traces and tilting homes. GPS stations detected the ground sinking and rising over a big space.

Geologists from the Icelandic Met Office interpreted the occasions as proof {that a} basalt dike – pressurized magma that forces its approach right into a fracture – had intruded beneath Grindavík. The exercise there had tapered off by early December, however 2.5 miles (4 kilometers) north of city, the bottom beneath the Svartsengi geothermal energy plant was transferring.

A map shows the location of the fissure.
The situation of the fissure the place magma erupted beginning Dec. 18, 2023, a number of miles from the city of Grindavík and simply east of Svartsengi energy plant and ajacent Blue Lagoon thermal spa. Icelandic Met Office

The bottom had dropped 10 inches (25 centimeters) because the basalt dike crammed, however then it started to rise in a broad dome, indicating that magma was reinflating and repressurizing the magma chamber. The end result was the close by eruption on Dec. 18.

If the fissure continues to propagate to the south, or if a big quantity of lava erupts, the evacuated city of Grindavík, with a inhabitants of round 3,500, could also be at risk. The lava might additionally spill to the northwest towards the ability plant, though the utility constructed rock partitions to attempt to divert lava flows.

Iceland is named “the land of fireside and ice” for a motive. Its residents have realized over centuries to dwell with its overactive geology.

The rationale for volcanism has two elements: One has to do with what geologists unimaginatively call a hot spot, and the opposite entails big tectonic plates which can be pulling aside proper beneath the island. As a geologist, I research each.

Life on the sting of two tectonic plates

When plate tectonic theory was rising within the Sixties, geologists realized that many volcanoes are situated in zones the place tectonic plates meet. Tectonic plates are gigantic chunks of Earth’s inflexible outer layer that carry each continents and oceans and are consistently in movement. They cover the planet like massive items of a spherical jigsaw puzzle.

Many of those volcanoes are in subduction zones, just like the Pacific’s Ring of Fire, the place thinner oceanic plates slowly sink into Earth’s mantle. These are the postcard stratovolcanoes like Mount Fuji, in Japan, or Mount Rainier, outdoors of Seattle. Due to their excessive gasoline content material, they have an inclination to erupt catastrophically, capturing ash excessive into the environment with the power of nuclear bombs, as Mount St. Helens did in 1980.

A second, sometimes quieter type of volcano kinds where plates pull apart.

The volcanic exercise close to Grindavík is straight associated to this type of plate tectonic movement. The mid-Atlantic ridge between the Eurasian and North American plates cuts proper via that a part of the island.

A map shows details of midocean ridges looking like seams on a baseball as they wind through the major oceans.
Within the Nineteen Fifties, cartographer Marie Tharp used echo soundings gathered by ships to develop the primary map displaying the ocean flooring intimately. It clearly revealed the mid-ocean ridges. This hand-painted model of her map consists of annotations displaying scorching spot tracks associated to motion of the plates. Heinrich C. Berann via Library of Congress; annotations by Jaime Toro

In reality, at Thingvellir National Park you’ll be able to actually stroll between the 2 tectonic plates. You’ll be able to see the topographic scars of the rift within the lengthy, linear valleys that stretch to the northeast from Grindavík. They align with the swarms of earthquakes, the ground deformation, and the fissure eruption of 2023.

The place plates draw back from one another, the underlying mantle rises towards the floor to fill the hole, carrying its warmth with it and transferring into an space of decrease stress. These two processes trigger melting at depth and volcanic exercise on the floor.

That is the same process that creates new oceanic crust underwater at mid-ocean ridges. After the magma solidifies as basalt rock, it should seem like vertical partitions intruded into the encompassing space.

The uplift is in a large area that includes a nearby power plant and the Blue Lagoon thermal spa.
A map exhibits the uplift of the bottom (vivid purple) north of Grindavík previous to the Dec. 18, 2023, eruption, in addition to the extent of the brand new lava circulate (black). Icelandic Met Office

Sitting on a scorching spot

In Iceland, the massive volcanoes within the inside additionally appear to be over a mantle plume, similar to Hawaii.

This sort of volcano sometimes erupts basalt lava, which melts at very excessive temperature and tends to circulate simply. Eruptions are usually not explosive as a result of the runny lava permits gases to flee.

Precisely what causes scorching materials to rise at scorching spots remains to be debated, however essentially the most generally accepted concept is that they’re brought on by plumes of super-heated rock that originate on the transition between Earth’s metallic core and rocky mantle. Scorching spots are a mechanism for the Earth to provide off a few of its internal heat.

YouTube video

How scorching spots develop. Video by Volcano Museum.

Sometimes, fissure eruptions are usually not explosive. Nonetheless, when lava that is 1,800 degrees Fahrenheit (about 1,000 levels Celsius) hits water, the flash to steam may cause explosions that may scatter ash over a bigger space.

A silver lining of Iceland’s volcanoes

Residing in an energetic volcanic space has some benefits, significantly for power.

Iceland derives 30% of its electrical energy from geothermal sources that use underground warmth to drive generators and produce energy. It’s nearly like a managed model of a lava circulate hitting the ocean, and it helps make Iceland one of the cleanest economies on Earth.

People sit in an eggshell-blue lake surrounded by black lava rocks. Steam rises in the background.
Iceland has quite a lot of pure scorching springs, however its Blue Lagoon has an uncommon origin linked to geothermal power. Photo by Jeff Sheldon on Unsplash, CC BY-ND

The Svartsengi hydrothermal plant makes use of the underground warmth from the identical magma chamber that’s now erupting to offer scorching water for a number of thousand properties, plus 75 megawatts of electrical energy.

That energy plant can also be a part of the explanation the Blue Lagoon is so standard. When the ability plant was inbuilt 1976, the plan was to discharge its nonetheless scorching wastewater into an adjoining low space, anticipating that it will seep into the bottom. Nonetheless, the geothermal water was loaded with dissolved silica, which grew to become stable minerals when the water cooled, creating an impermeable layer. A small lake started to kind.

Due to its excessive silica content material, the water on this lake is a spectacular blue shade that impressed the creation of the geothermal spa. The Blue Lagoon is likely one of the top tourist attractions in the country.

Now the Blue Lagoon is in danger: Typically the volcano provides, typically it takes away.

That is an up to date model of an article published Nov. 15, 2023.

Article written by Jaime Toro, Professor of Geology, West Virginia University

This text is republished from The Conversation beneath a Inventive Commons license. Learn the original article.

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