Archaeologists use growth rings on trees, then compare their findings to calibration charts, after unearthing many ancient bog oaks, they discovered that there was no growth rings between the dates above. What had happened? Had there been a climatic catastrophe, from a volcanic eruption, or perhaps a comet that collided with Earth, or a comet passing close to Earth and the dust from its tail blocked out the sun? There was a thriving settlement at Dartmoor, which is now called Grimspound, agriculture was going on here and many post-holes of roundhouses have been discovered, but all the inhabitants left as Dartmoor became an infertile plain, which it is to this day. Grimspound was not unique, as all over Britain and Ireland, high farming ground was turning to moorland, between these years BC. The old agricultural world was falling out of use and a new age was dawning.