The Quaternary ice ages

At the end of the 18th century, advances in natural sciences led to the discovery of fossil cold-adapted animal species that had become extinct a few thousand years ago and the existence of glacial landforms and sediments in European regions located far from mountain areas where glaciers still existed. The early 19th century saw the development of theories about the existence of ice ages during the Quaternary period, coinciding with the appearance of humans. By the end of the 19th century, the extent of glacial landscapes in Europe had been recognised. Throughout the first half of the 20th century, the main glacial landforms were delimited both in mountain ranges and in Central and Northern Europe. Since the middle of the 20th century, a progressively more accurate chronology of numerous glacial cycles has been established with the application of radiocarbon dating and the oxygen isotope analysis of foraminifera in marine sediments. Furthermore, the existence of such cycles has been related to changes in the Earth’s orbit, climatic and oceanic effects of which in the Northern Hemisphere caused the growth of ice sheets, in several pulses with an average duration of ~100 ka over the last 10 glacial cycles. When ice sheets reached a critical maximum, a complex series of reverse processes in the atmosphere and the oceans led to the rapid disappearance of the northern continental ice sheets in about 10 ka. At the end of each glaciation, warmer interglacial periods of about 15–10 ka have occurred, and have been followed by a gradual descent into a new period of glaciation.