Rock reveals that Earth already had a magnetic field 3.7 billion years ago (remarkably similar to today’s Earth’s magnetic field)

Scientists have – finally – found hard evidence that can accurately date the age of Earth’s magnetic field. Not only that; the same evidence shows how strong the field must have been at the time.

It was certainly not easy, but the result is impressive: evidence has finally been found that can be used to date the magnetic field. This is evident from a recent study conducted by scientists from England. For this research they traveled to the Isua Supracrustal Belt in southwestern Greenland. The Isua Supracrustal Belt is also called the Isua Greenstone Belt and has been dated during previous research as one of the oldest rock formations in the world: approximately 3.7 billion years old. Lead researcher Claire Nichols contributed to the study. She says: “It was very difficult to obtain reliable information from rocks that are so old. It was very cool to see the first magnetic signals during the analysis in the lab afterwards. Ultimately, we are trying to find out more about the period when life first appeared on the surface of the Earth – and what role the magnetic field played in this. This discovery represents an important step forward in that process.” The research has been published in the journal Journal of Geophysical Research Solid Earth.

Small magnets
For the research, the scientists examined stones from Greenland. These stones have multiple layers of iron particles that are clearly visible. These iron particles contain incredibly valuable information: when iron particles become very warm, they start to behave like small magnets, often copying the strength and direction of the magnetic field. This is the core of the hard evidence: by reading this information in a lab, it was ultimately discovered what the state of the magnetic field was at the time the Isua Supracrustal Belt was formed; or 3.7 billion years ago. These results show that the magnetic field used to have a strength of approximately 15 microtesla. According to the scientists, this is comparable to the current strength of the magnetic field, which is about 30 microtesla.

Solar wind
The results of the study are significant for several reasons. First, the results are surprising because they show that the magnetic field is much older than previously thought. It is very surprising that the strength of the magnetic field 3.7 billion years ago was quite comparable to the strength that the magnetic field has today.

More detailed
It is not the first time that scientists have tried to determine the age of the Earth’s magnetic field and the strength that the Earth’s magnetic field had in the past. But previous studies mainly used samples of loose rocks and crystals to learn more about the age of the magnetic field. For this study, the scientists used samples from a larger rock formation, ultimately making the results more reliable.

However, there are also many other reasons why the results are important for science. As Nichols previously pointed out, the researchers ultimately hope to learn more about the strength and precise role of the magnetic field over the years. The new research can help with this. The scientists point out, for example, that the magnetic field has long been protecting us against external dangers, such as cosmic radiation and charged particles from the sun – also known as the ‘solar wind’. However, scientists estimate that the effect of the solar wind on Earth used to be much more intense than it is today. It tentatively hints that the Earth’s magnetic field – which must have been about as strong 3.7 billion years ago as it is today – has gradually started to offer more protection to the Earth’s surface. And that would then have offered the first animals the opportunity to leave the oceans – which they previously needed to be protected from the charged particles of the sun – and to live on land.

Dynamo
Finally, there is also one last important reason to mention; the magnetic field can teach us more about the origins of the earth. The magnetic field is created by a dynamo effect caused by movements of iron particles in the liquid outer core of the Earth, which ultimately generates electricity. To keep this effect going, a hard inner core is needed, in which the molten iron particles continue to move due to their buoyant force. However, in the past – when the Earth was only just formed – it did not yet have a hard inner core, which has caused scientists to wonder for some time whether the Earth already had a magnetic field. According to the scientists behind this new research, their results indicate that this was the case: they also suspect that the mechanism that was behind the creation of a geomagnetic field in those early years of the Earth worked just as efficiently as the ‘dynamo’. ‘ who is responsible for this today.