The terrifying sounds that hinted Iceland's volcano was ready to blow: Audio clip reveals the seismic activity in the build up to the eruption

Iceland's fears were confirmed on Tuesday morning as a volcano erupted just south of the capital following a 'swarm' of earthquakes in the Reykjanes Peninsula.

The nearby fishing town of Grindavík and the five-star Blue Lagoon hotel were evacuated as a 1,200-metre-long fissure sent lava pouring through defensive barriers.

Now, scientists have revealed the terrifying sounds that hinted the eruption was about to occur. 

Earthtunes, an app developed by Northwestern University, turns the lines scratched onto a seismograph by tremors in the Earth into a soundtrack worthy of a horror film.

In this terrifying recording, you can hear the approach of the 'earthquake swarm' which preceded the eruption.

According to the Iceland Meteorological Office (IMO), the swarm began around 6:30am local time (07:30 BST).

The IMO says these tremors were a 'clear sign of the onset of a magma intrusion' ahead of the eruption which began at 09:45 local time (10:45 BST).

Later in the clip you can even hear the boom of a magnitude 5.3 earthquake that could be felt throughout southwest Iceland.

Yesterday's eruption was the eighth to hit the Reykjanes Peninsula since 2021, when the region entered its latest active period.

However, as the lava began to burst from the Sundhnúkur crater row, experts warned that this would be 'much larger' than previous events.

In the recording, you can hear the slight rumble of the fissure opening at 09:45, just north of the protective barriers around the town of Grindavík.

While the seismic audio captured by Earthtunes appears to become quiet, the fissure continued to grow into the morning.

By 12:35 local time, the IMO reported that the eruptive fissure had grown to about 1,200 metres in length.

Additionally, a second fissure had opened a few hundred metres inside the protective barriers around Grindavík, between the barriers and the town itself.

Later, the IMO reported that a hot water pipeline in northern Grindavík had been broken, which 'confirms that significant fault movements have occurred within the town.'

In addition to seismic activity, the Earthtunes audio also records what appears to be a 'clinking' sound.

Professor Valentin Troll, a volcanologist from Uppsala University, told MailOnline this could be the sound of rocks blasted into the air by the eruption landing around the recording device.

Professor Troll says that this sound is 'very characteristic' of volcanic eruptions he has studied in the past.

Yet, even as volcanic activity diminished and the lava flow slowed, intense earthquake activity continued all along the line of the magma intrusion.

The largest of these tremors could be felt in the town of Volgar, about 4.3 miles (7km) north of the eruption area.

According to data from the United States Geological Survey, three major earthquakes struck the Reykjanes Peninsula around the time of the eruption.

A pair of magnitude 4.6 and magnitude 5.2 earthquakes struck to the north of Grindavík shortly before 18:00 local time (19:00 BST).

Meanwhile, a magnitude 4.9 tremor occurred under the sea just 3.7 miles (6km) to the south of the fishing village.

Around this time, the Earthtunes recording reveals a booming sound like a slamming door which Professor Valentin says is 'absolutely' the sound of an earthquake.

Worryingly, this recording suggests that seismic activity is shifting further northwards towards the more populated regions.

'The earthquake swarms have migrated further north than in any of the previous eruptions,' says Professor Troll.

'This likely heralds that there may be a fracture forming in the next eruption which could hit the northern highway which connects the airport with Reykjavik.'

With some earthquakes now emerging less than a kilometre from the highway, Professor Troll warns there could be an eruption that destroys the road in the coming weeks or months.

Since Iceland is so dependent on imports for much of its food supply, this would cause a 'severe infrastructural problem'.

Icelandic authorities have been preparing the smaller domestic Reykjavík Airport to accommodate larger planes and have made provisions for emergency alternative routes.

Iceland is a particular hotspot for seismic activity because it sits on a tectonic plate boundary called the Mid-Atlantic Ridge which is gradually pushing North America and Eurasia away from each other.

There are only a few places on Earth where the Mid Atlantic Ridge is exposed on land, but Iceland – which is slap bang in the middle of the ridge – is one of them.

An eruption rocked the region in November, which in turn was the seventh eruption in a year.

Most of Grindavík’s 4,000 residents were evacuated in late 2023, shortly before the first volcanic eruption in the area.

Since then, almost all the houses have been sold to the state, and most of the residents departed.

Regional police said they had completed the evacuation of Grindavík, with the exception of a small number of residents who had refused to leave.

Runólfur Þórhallsson, Iceland’s director of civil protection, urged those who had chosen not to leave the town to evacuate.