Scientists have been able to improve the timeline of the Viking presence in North America thanks to new archaeological evidence.
A team of archaeologists from the University of Groningen, the Netherlands, has determined that pieces of wood with cut marks have been dated precisely to 1021 CE exactly 1000 years ago. The metal tools that created those marks were not made by the native population.
Vikings did however make and use metal tools and are known to have settled at L'Anse aux Meadows where the wood was discovered.
Researchers claim that this is the earliest and best date for European settlement in the Americas. It also provides a reference point to understand the global transference and goods of knowledge and genetic information.
Since long, it has been known that Vikings arrived in North America at L'Anse aux Meadows, Newfoundland. This was well before Christopher Columbus arrived. It has been hard to find a precise date for this brief occupation.
However, archaeologists are increasingly making use of a unique and creative dating tool, dendrochronology. This is based on counting tree ring.
Microscopic detail of tree rings in a L'Anse aux Meadows fragment. (Petra Doeve)
It might seem difficult to find a piece of wood from unknown age. But, help is available from unexpected places: solar storms.
Radiocarbon-14 (or radiocarbon) is a radioactive carbon isotope that can be found abundantly. Radiocarbon is only found in trace amounts on Earth, compared to other carbon isotopes naturally occurring.
It forms in the upper atmosphere from the cosmic rays of space. The radiocarbon is produced when cosmic rays from space enter the atmosphere. They interact with local nitrogen atoms and trigger a nuclear reaction. Because cosmic rays stream through space continuously, Earth gets a steady supply of radiocarbon.
Tree rings naturally contain some of this radiocarbon. Every now and then, radiocarbon spikes in tree rings can be found, which fade over many years. These spikes are often interpreted as evidence for solar storms or solar flares, which is a significant source of cosmic radiation.
Tree rings from all over the globe have been found to show a similar solar storm. They are dated to 992-993 CE, and are based on radioactive decay of radiocarbon. Researchers also found this spike in four pieces cut wood from L'Anse aux Meadows.
Margot Kuitems, an archaeologist at the University of Groningen, stated that "Finding the signal of the solar storm... [in] bark allowed us to conclude the cutting activity occurred in the year 1021 CE."
Dendrochronology has been used by other researchers to reconstruct the history of ancient supernovae and solar activity. This discovery adds yet another feather to dendrochronology's cap. It shows that solar storms can also be used as a reliable reference point for contextualizing archaeological artifacts.
The researchers wrote in their paper that they have evidence that the Norse were present on North American continent in AD 1021.
"This date provides a safe juncture in late Viking chronology. It is also a point of reference for European cognizance about the Americas. This date also marks the first year that human migration has occurred on the planet.
Nature published the research.