As Iceland prepares for a possible volcanic eruption in the coming days, scientists predict that the country is in for decades of instability.
The eruption could cause significant damage to local infrastructure and release toxic fumes, but concerns have now been eased that there could be much more serious consequences.
Since the end of October, an increase in earthquake activity has been recorded in the southwestern region surrounding the Icelandic capital, Reykjavik.
This is caused by an underground river of magma - hot liquid or semi-liquid rock - about 15 kilometers long that moves upwards under the earth's surface.
It extends under Iceland and part of the Atlantic Ocean, and the impact of the eruption on the ground and on air traffic will depend on where exactly the magma penetrates to the surface.
Residents of the fishing town of Grindavik, which lies directly above the magma, have already been evacuated due to the danger of "fountains of fire" and the emission of harmful gases.
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After an 800-year hiatus, eruptions on the Reykjanes peninsula started again in 2021, which could mark a new "eruptive cycle", Matthew Roberts of the Icelandic Meteorological Service told the BBC.
"We expect there to be volcanic eruptions along the peninsula, not just multiple times in the same location," he adds, warning of possible volcanic instability in Iceland in the coming decades.
"Grindavik is very close to the location of the new fracture, and its survival is far from certain. It all depends on where the magma ends up reaching the surface, but the situation doesn't look good for the city's residents," said Bill Maguire, the university's professor of geophysics and climate risk.
If a volcano erupts at sea, or erupts on land and then flows into the sea, then there is a risk of an explosive ash cloud because the super-hot rock will come into contact with the water.
In April 2010, the eruption of the Eyjafjallajökull volcano caused the largest closure of European airspace since World War II due to a huge ash cloud.
At that time, the losses of the aviation industry were estimated at between 1,5 and 2,5 billion euros.
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Current volcanic activity is such that such a large impact is not expected.
"The 2010 Eyjafjallajokull eruption was quite different because it was associated with a glacier-topped volcano.
"The interaction of magma with ice and water made the eruption so explosive and dangerous for aviation. Now that's not the case," says Dr Michele Paulato, a volcanologist at Imperial College London.
The Icelandic Meteorological Office estimates that the magma is currently less than 1.000 meters from the eruption, and therefore the probability of an eruption is "high" and could be expected in the coming days.
The earthquakes continue to weaken, but the ground is already deformed, with one-metre-deep cracks in the roads, suggesting magma may be even closer to the surface - a sign that a peak is approaching.
"For the last few years, there have been softenings and pauses in earthquakes before volcanic eruptions occur," Evgenia Ilyinskaja, an Icelandic geophysicist and co-director of the International Volcanic Health Hazard Network, told the BBC.
Dr Roberts, director general of the Icelandic Meteorological Service in Reykjavik, showed BBC reporters a room where seismic activity is monitored 24 hours a day.
The team was shocked when they realized on November 10 that magma was flowing into the ground, fracturing the rock along 15 kilometers.
It cut under Grindavik "almost like an underground freight train," says Dr Roberts.
A phenomenon unknown in modern times.
An order for immediate evacuation was issued, and soon after that roads began to crack, and houses were increasingly damaged.
The western part of Grindavik has sunk by more than a meter since November 10 and continues to sink by four centimeters a day.
Seismologists were additionally surprised by the fact that magma flows under the previous, centuries-old, visible crack.
"She found the same place again," says Dr. Roberts.
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Iceland is used to volcanic activity because it sits above the Mid-Atlantic Ridge.
The Eurasian and North American plates are moving away from each other a few centimeters every year.
But an evacuation like this has not happened in 50 years.
In 1973, a fissure began spewing molten red lava on Heimej, the largest island in Iceland's Westman archipelago.
On the Reykjanes peninsula, it is currently estimated that the magma is about 800 meters below the surface.
Residents will likely have to wait several weeks before it is clear whether they can return to the area.
"We don't expect an explosive eruption," says Dr Roberts, adding that this is not necessarily a good thing.
A low-intensity eruption could cause several weeks of lava to flow from a series of fissures.
"If that were to happen, there would be a flow of lava to the south - probably towards Grindavik - and also probably to the north and west" towards the Svartsengi power station and the Blue Lagoon, says Dr Roberts.
Emergency teams are already building protective barriers, known as dykes, near the geothermal power plant, while the famous Blue Lagoon spa remains closed.
Iceland has a host of ingenious ways to combat lava, says Dr Roberts, but "nature always wins if the eruption lasts long enough".
Iceland is so used to volcanic activity that it has made a successful tourism industry out of it because it sits above the Mid-Atlantic Ridge.
The Earth's crust is divided into different plates, and as the Eurasian and North American plates move several centimeters a year, this allows magma to erupt to the surface in the form of lava and/or ash.
The nature of volcanic eruptions varies depending on the type of rock and the way the plates move.
One of the largest eruptions in Iceland was back in 1783 when there was a lava flood that lasted for eight months and produced large sulfur clouds that hovered over northern Europe for more than five months.
It is estimated that they caused a cooling of about 1,3 degrees Celsius in the next two years.
"On Friday and Saturday, November 10 and 11, it looked worrying that we could have something of that scale, which would have huge implications for air quality in the Northern Hemisphere.
"We shouldn't expect something like that now. The latest data indicate that the eruption will be much smaller than initially assumed," says Dr. Iljinskaja, who is in regular contact with geologists on the ground.
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