Cale Matthews, BTN Reporter: The town of Grindavik in Iceland is slowly being ripped apart.
Icelandic Policeman: Everyone is really concerned about their home. There is some volcanic activity going on, very high activity.
Grindavik Resident: Earth can just open up and swallow you, you never know.
Icelandic Official: This is an this ongoing situation and the people of Grindavik will not be able to, to go back for a long time.
Everyone’s worried about a volcano under the Reykjanes Peninsula erupting. So worried, the entire town's been evacuated and probably won't be allowed back for months. But just two years ago, about 20 minutes up the road, this happened and no one seemed to care.
Icelandic Resident: This is my fourth eruption I think, or fifth.
Icelandic Resident: Man I just got off work and right here.
The town wasn't evacuated and the volcano became a sausage sizzling tourist attraction. Iceland and volcanoes go hand in hand. But why are some nicknamed by locals as tourist eruptions, while others can be life changing?
Grindavik Resident: I, I don't think we'll ever feel safe after knowing what has happened there.
When you look at a map of all the volcanoes in Iceland, compared to where everyone lives, it starts to make sense. More than two thirds of the population, 220-thousand people live here in the greater Reykjavik area. In the last 500 years, about one-third of Earth's total lava flow has poured out of Icelandic volcanoes. And while eruptions occur every three to five years, more often than not they happen far away from towns and people.
Pall Einarsson, Geophysicist: There are only two towns in, in the whole country that have this special situation of being located within the volcanic zone so that volcanic eruption is possible within the town limits.
But to really understand Iceland’s unique volcanic landscape, you need to look below the surface.
The country sits above a hotspot, a big build-up of hot melted rock known as magma deep below the surface. It's also on the border of two tectonic plates, the North American plate and the Eurasian plate that are slowly pulling apart from one another, forming what's known as the Mid Atlantic Ridge. As the plates pull apart, the magma rises from the asthenosphere to the surface, sometimes spilling out as lava and then cooling to form new rock. You can actually see the plates ripping apart at the Thingvellir National Park.
Pall: Iceland is really made by volcanism. Without the volcano there would be no Iceland.
Straddling the ridge between these plates are most of Iceland's volcanoes. But if we zoom in, you'll find the town of Grindavik. Over the last month, there have been thousands of earthquakes as magma has slowly pushed its way to the surface. It's created a 15-kilometre long crack and right now the magma is sitting about one and a half kilometres below the ground, threatening to spew out as lava and essentially destroy the town. It's the start of what many say is a new chapter of volcanic activity in this part of Iceland.
Pall: We are at the beginning of an active period that may last with off and on eruptions every decade, year or whatever, we don't really know what's ahead.
But it's not the only type of eruption in the Land of Fire and Ice. Very broadly speaking, volcanic eruptions are grouped into two different categories, effusive or explosive. Effusive eruptions are where most of the magma flows out as lava, while explosive eruptions are where most of it is ash or tephra. The recent eruptions along the Reykjanes Peninsula have been effusive. This happens when really hot, runny magma rises slowly to the surface. Its runny nature means any gas in the magma can easily escape, meaning the lava flows out with very little pressure. Generally, effusive eruptions are slow moving, and don't pose a massive threat. This map shows where lava has flowed across Iceland in the last one thousand years, and while it's generally away from people, this study from 2008 actually said that Grindavik was of special concern when it came to lava flows.
About 75 percent of eruptions in Iceland though are explosive, and this can create much bigger problems. Explosive eruptions happen when cooler, thicker magma traps gases in the mixture. The gases propel the magma to the surface at a much higher speed. The gases build pressure in the magma, and then can eventually explode through cracks or fissures in the Earth's crust like this. These eruptions can create massive plumes of ash or tephra, which extend kilometres into the sky, and they can create serious problems for nearby towns, with chemical elements being trapped in the tephra. In the past, explosive eruptions in Iceland have led to the death of livestock and the poisoning of water supplies making people pretty sick. This map shows just how far reaching ash fall-out has been over the last one thousand years. But one of the more famous eruptions this century is the 2010 eruption of Eyfjallajokull. This is what's known as a phreatomagmatic eruption, and it's common in Iceland. Phreatomagmatic eruptions occur when magma meets water and in Iceland this comes in the form of volcanoes covered by glaciers or ice caps or the ocean. These explosive eruptions can create giant plumes of steam and ash, which is what happened in 2010.
News Reader: Above Iceland volcanic ash is still spewing into the air.
Although Eyfjallajokull wasn't a powerful eruption, it was long lived, erupting for 39 days spewing ash nine kilometres high.
Person: We can't get a flight guaranteed 'til Monday and I don't even know if that would fly.
European airspace was shut down for eight days, with more than 100-thousand flights being cancelled. Not only to phreatomagmatic eruptions create high plumes of ash, they can cause something called Jokulhlaups.
Jokulhlaups are big glacial outbursts or floods that can happen either during eruptions or when magma beneath the surface melts glaciers. This melt water can create mega floods that can inundate nearby towns and erode the surrounding landscapes. This map here shows the impact Jokulhlaups could have on nearby towns. If Iceland's largest volcano, Katla, were to erupt, it'd result in the evacuation of thousands of people in nearby towns due to the hazard Jokulhlaups present.
Seismic activity around Grindavik has calmed down in the last couple of days, but while residents have been allowed to check on their homes during the day, no one is sure when the town will be allowed to move back in.
Grindavik Resident: Houses are ruined. It's, it’s very sad because I'm born and raised there.
Grindavik Resident: Our house is still okay. But I don't know what will happen in the next days, weeks.
Grindavik Resident: We have a home here, we have a company, and we’re about to lose everything.
Grindavik Resident: You don't think it's real. I feel like I've accepted that I won't probably come back here.