When was the last tragic volcanic eruption

Volcanic eruption in Iceland: this may just be the beginning

Instead, the magma layer, a so-called dyke, migrated underground over the next few weeks. Seismic activity and the changing shape of the ground allowed scientists to roughly track its movements. They caught him shuttling back and forth between the northeast and southwest of the peninsula, creating cracks in the ground above.

“I ended up calling him the Reluctant Dyke because he didn't seem to know what to do,” says McGarvie. He seemed to be looking in vain for a place to break through the surface.

Seismic activity in the region has decreased in recent weeks. Since most dykes cool and freeze before they have a chance to erupt, some scientists suggested that an eruption would not happen after all.

Iceland's top crust, however, has a peculiarity: It is slightly elastic - that is, it is more like toffee than hard candy. The crust in this area can stretch a little to make room for magma. This allows the dyke to penetrate the rock just below the surface without causing large cracks and generating the tell-tale acoustic signals.

This stealth is typical of eruptions that occur along crevices, as was the case on the peninsula. The scientists in Iceland “had just been in the field and suddenly the ground opened up,” says Ágústsdóttir. Apparently, the declining seismic activity in this region is not a sign of calmer days, but could actually be a harbinger of an eruption.

The long awaited outbreak

On March 19, the Icelandic Meteorological Bureau recorded a couple of low-frequency earthquakes, possibly caused by magma moving towards the surface - but those were very subtle events, says Ágústsdóttir. Unable to know when and where an eruption would occur, local authorities continued to advise people to stay out of the crevasse area.

That evening, the lava began to erupt near Fagradalsfjall, within the Geldingadalur - a natural depression whose name means eunuch valley (possibly a reference to the early settlers' practice of neutering animals in the area). After not finding an escape route to the northeast or southwest, the Dyke apparently broke through "in the middle because both directions were somehow blocked," says Tobias Dürig, a volcanologist at the University of Iceland.

A webcam on a nearby ridge caught the lava first. A Coast Guard helicopter was dispatched to the scene, and the pilot quickly spotted the glow of the lava flickering and hissing in the sky.

The lava initially poured out of a tortuous fissure 500 meters long, but over the course of the weekend the eruption was concentrated in a single spot, forming a steep, towering cauldron of freshly cooled rock. Smooth streams of lava wound around coarser lava with block-like debris. The lava flowing at a steady pace meant that the cone suffered some partial collapses in which it hurled lumps of lava over the scorched earth.