The concomitant earthquakes and lava flows would already obviously cause tremendous damage, but they are nothing compared to the twin threats of ash, and volcanic gases.
University computer models predict that if there's an eruption, the resulting lava flows probably won't impact any nearby towns or the region's international airport, but again, that's only based on models.
It typically erupts several times a year and in addition to the plumes of ash billowing from its crater, cameras recently recorded some amazingly vivid pictures of lava flowing downhill at night.
Rob Guzman and his husband fled their guest-house rental business just 10 km from the lava flow. They were worried about the ground shaking from the eruptions, clouds of sulfur dioxide gas and roads being closed.
The core is even hotter than the mantle and, as the descending sea floor reaches its outer surface, it's superheated and rises back up in vast plumes towards the surface.
A webcam set up by Iceland's Public Broadcaster, RUV showed a stream of lava flowing into Grindavik with the burning buildings, just meters away from houses.
But as temperature and pressure increase, it can become things like cristobalite, which is found in lava flows, or stishovite, which is in meteorite craters.