The Magnetic Anomalies of Iceland Showing the Background Story of Reykjanes Eruption

Volcanic eruptions have formed Iceland along with the tectonic drift. Magnetic anomalies have been mapped and analyzed, telling the story of how Iceland has evolved for millions of years. Grétar Ívarsson and others have shown this step by step. This topic is dealt with in the paper ‘Geology and geodynamics of Iceland’ by, R.G. Trønnes ( https://notendur.hi.is/oi/Pdf%20reprint%20library/Geology%20and%20geodynamics%20of%20Iceland.pdf)

The first map shows the conditions prevalent, where you find Iceland today, 8 million years ago. By then, the structure of Iceland was simpler than today. The mid-ocean ridges were rather directly connected, and the magnetic anomalies were aligned regularly parallel to the mid-axis of the ridge.

Magnetic anomalies – 8 million years old axis.

The square with dotted lines indicates where the West Rift Zone was going to form. A NS-axis could be defined, similar to the one found to day within the North Volcanic Zone of Iceland.

Then the West Rift Zone of Iceland started to emerge. The West Rift Zone is a term combining the areas often referred to as the West Volcanic Zone and the Reykjanes Oblique Rift.

Magnetic anomalies – 6 million years old axis.

About 6 million years ago, the rift axis stopped spreading north of the 64th latitude. Rifting started farther to the east and the West Volcanic Zone started to form, offset from the Reykjanes Ridge. The rift zone cuts through older parallel anomalies east of the old axis from the NE, as the older ones were oriented NS. Therefore, the pattern of anomalies becomes more complex. At the same time, a new NS-axis started replacing the old one.

Magnetic anomalies – 4 million years old axis.

Now the West Rift Zone (WRZ) had developed withn the framed part. The new NS-axis had shifted eastwards, as it adds constantly material symmetrically to both sides.

Magnetic anomalies – 2 million years old axis.

Now, the new East Volcanic Zone starts to propagate to the south-west from the North Volcanic Zone.

Magnetic anomalies – as measured today.

Today, we see this pattern of magnetic anomalies in Iceland. As expected, they show the same characteristics of geological features as other types of mapping. Pointing out the site of the eruption taking place in Geldingadalir and Meradalir on the Reykjanes Peninsula of Iceland today, it can be easily understood that it is an important volcanic area. If you trace the maps one by one, it can be argued that this eruption is actually found at the spot from where all the development of the volcanic zones of Iceland started 8 million years ago, leading to the situation we learn about today!

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