Christopher Seddon

“Ice Age 2,588 million years ago, at the start of the Pleistocene, the Earth entered an Ice Age. It followed 50 million years of climatic downturn, and was the first full-blown ice age for a quarter of a billion years. Cooler, arid conditions alternated with warm, wet conditions as ice sheets ebbed and flowed in higher latitudes. The ice sheets alternately locked up vast amounts of fresh water, then released it again as temperatures rose. This alternation between a cooler and a warmer climate has continued right up to the present day. The cold spells are often referred to as ‘ice ages’. In particular the end of the most recent glacial period 11,600 years ago, is popularly known as the end of the last Ice Age. In fact the warm spells – interglacial periods – are no more than breaks in an on-going ice age. The current Holocene epoch, that followed the last glacial period, is such a break. In theory, glacial conditions will one day return, though the effects of anthropogenic (human caused) global warming make this uncertain. Glacial periods are not necessarily periods of unremitting cold, but alternate between colder and warmer intervals known respectively as stadials and interstadials. The idea that there were periods when glaciers extended beyond their present-day limits gradually emerged during the first half of the nineteenth century. Geologists sought to explain such phenomena as rock scouring and scratching, the cutting of valleys, the existence of whale-shaped hills known as drumlins and the presence of erratic boulders and ridges of rocky debris known as moraines. The term Eiszeit (‘ice age’) was coined in 1837 by the German botanist Karl Friedrich Schimper.”
― Christopher Seddon, Humans: from the beginning: From the first apes to the first cities