A climate archive in the mountains of Galicia
High in the Trevinca Massif, a mountain range reaching 2,127 meters at Pena Trevinca, lie a series of small lakes carved by ancient glaciers. These lakes, including Lagoa da Serpe and Lagoa de Ocelo, hold a scientific record within their muddy bottoms. The lakebeds contain layers of sediment deposited year after year for millennia, trapping pollen, charcoal, and minerals from the surrounding environment. By drilling long tubes into this mud, scientists extract sediment cores that provide a detailed timeline of past climate and vegetation.
The geology of the Trevinca Massif consists of metamorphic rocks like gneiss, schist, and slate, which were deformed during the Variscan orogeny. During the Pleistocene, an extensive icefield covered this region, with glaciers carving out the U-shaped valleys and cirques that are visible today. The ice reached a thickness of over 500 meters in the Bibei valley. As the glaciers retreated at the end of the last glacial period, they left behind moraines (ridges of rock and debris) and depressions that filled with water, forming the lakes we see today. The undisturbed sediment layers in these lakes record this period of environmental change.