Over the past millennia, the strength and direction Earth's magnet field have changed significantly. Scientists are keen to analyze its past patterns in order to predict how it might change in future. This is a vital research field considering that this magnetic shield protects us against harmful cosmic radiation.
Instruments capable of measuring the Earth's magnetic field directly have been available for only 200 years. We have to look at other methods to track the magnetic field further back in history. A new study has revealed that artifacts from Jordan were found to date to between 8,000 and 10,000 years ago. This is known as the Neolithic or New Stone Age.
These special items, including ceramic pottery and burnt flants that were used to make other tools, are unique because they were created at extremely high temperatures.
The heating and cooling of the artifacts caused some minerals and crystals to freeze a record of Earth's magnetic field at that time. This phenomenon is known as residual magnetization or remanent magnification.
Erez Ben-Yosef, an archaeologist from Tel Aviv University in Israel, says that this is the first time that burned flints taken from prehistoric sites have been used to reconstruct the magnetic fields from their time period.
"Working with this material expands the research possibilities tens to thousands of years ago, as humans used the flint tool for a very long time before the invention of ceramics."
The excavation site in Jordan. (Thomas E. Levy)
Researchers looked at 129 items, building upon previous work that evaluated the viability to use flint fragments to guide magnetic field strength. This is an extremely useful tool for future research.
The team discovered that there was a decline in the strength the magnetic field at the time artifacts were used, and then a recovery over a period of several hundred years. This is not long in the grand scheme for the planet's past.
It's important to remember that Earth's magnetic field is becoming weaker over time, which can be a source of concern. However, this doesn't necessarily mean that our protective bubble will disappear in the next few decades.
"The results of our study can be reassuring: This has already occurred in the past," Lisa Tauxe, geophysicist at Scripps Institution of Oceanography says.
"Approximately 7.600 years ago, the magnetic field strength was lower than it is today. However, within 600 years, it gained strength again and rose to high levels."
Although it is believed that the magnetic field of our planet is created by convection currents from molten iron or nickel circulating in Earth's outer core, approximately 3,000 km (1,864 mi) below ground, there aren't many other facts that we know.
Some questions remain unanswered about this amazing phenomenon, including how the magnetic field may be related to changes in Earth's atmosphere and climate.
Geological studies can track shifts in Earth's magnetism over time, but they are not as precise in timing as archaeological analysis. This is what this study shows.
"The origins and essence of the magnetic field have remained largely unresolved." Ben-Yosef says that during our research we tried to find a way into this great riddle.
The research was published in PNAS.
