The term ice age was first applied in 1837 by the botanist Karl Schimper (following the proposition of theories by, among others, the Swiss civil engineer Ignace Venetz in 1821 and the Swiss naturalist Louis Agassiz in 1837 in contrast to the held belief that the rocks and sediment left behind were caused by the biblical flood) to refer to a period of glaciation occurring in the Earth' s history, but is particularly applied to that in the Pleistoceneepoch, immediately preceding historic times when an ice sheet spread over northern Europe, leaving its remains as far south as Switzerland. There were several glacial advances separated by interglacial stages during which the ice melted and temperatures were higher than today. There were once thought to have been only three or four glacial advances, but recently it has been discovered that about twenty major incidences have occurred during earth's history. Other ice ages have occurred throughout geological time: there were four in the Precambrian era, one in the Ordovician, and one at the end of the Carboniferous and beginning of the Permian. The occurrence of an ice age is governed by a combination of factors known as the Milankovitch hypothesis: firstly, the Earth's change of attitude in relation to the Sun; and secondly the 92,000-year cycle of eccentricity in the earth's orbit around the Sun, changing it from an elliptical to a near circular orbit, the severest period of an ice age coinciding with the approach to circularity. Research Ice Age
Abbreviations
Research Ice Age
