These eruptions likely cast a volcanic winter over the northern hemisphere, impacting the trees at Mount Iškoras in Norway, where the study was conducted. "Blue rings look like unfinished growth ...

which found strange blue rings in samples of trees and shrubs from the northern treeline in Norway. “Blue rings look like unfinished growth rings, and are associated with cold conditions during the ...

Trees need a certain ... Iškoras in northern Norway. The team cross-sectioned and stained these samples, then photographed them under a microscope so that growth ring widths could be measured ...

These “blue rings ... Norway, where these plants battle harsh Arctic conditions. Here, at the northern limit of where trees can survive, they uncovered a natural record of historical cold events ...