As the Vikos Gorge is a deep cross section of the mountain, its slopes expose a series of rock formations of various ages. The upper layers, at a depth of 0–, consist of relatively young Eocene limestone, at a depth of – they consist of a stratum from the Campanian era, while below they consist of Jurassic and Cretaceous limestone. In the deepest layers, grey Jurassic dolomite is dominant. Sedimentary and lithological investigation in the Voidomatis basin revealed that the innermost alluvial deposits consist of limestone-derived material, carried by the Voidomatis river from higher elevations by glacial action about 30,000 years ago. The subsequent (middle) deposits are the product of de-glaciation and the extended run-off from the uplands about 20,000 years ago, while the outer unit is attributed to human activities associated with pastoralism, which caused extended deforestation and soil erosion. The Voidomatis basin contains evidence for three major phases of glaciation, with the two largest and earliest taking place during the Middle Pleistocene. The final phase of glacial activity probably occurred during the Last Glacial Maximum, between 22,000 and 20,000 ago.