The last glacial period or ice age, began about 110,000 years ago and lasted until around 10,000 years ago. The last glacial maximum, which means when there was the most ice present during that ice age, was about 18,000 years ago.
There have been several “ice ages’ throughout earth’s existence.
The earliest hypothesized ice age is believed to have occurred around 2.7 to 2.3 billion (109) years ago during the early Proterozoic Age.
The earliest well-documented ice age, and probably the most severe of the last 1 billion years, occurred from 800 to 600 million years ago (the Cryogenian period) and it has been suggested that it produced a Snowball Earth in which permanent sea ice extended to or very near the equator.A minor ice age occurred from 460 to 430 million years ago, during the Late Ordovician Period.
There were extensive polar ice caps at intervals from 350 to 260 million years ago, during the Carboniferous and early Permian Periods, associated with the Karoo Ice Age.
The present ice age began 40 million years ago with the growth of an ice sheet in Antarctica, but intensified during the Pleistocene (starting around 3 million years ago) with the spread of ice sheets in the Northern Hemisphere. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000 and 100,000 year time scales. The last glacial period ended about 10,000 years ago.
In between ice ages, there are multi-million year periods of more temperate, almost tropical, climate, but also WITHIN the ice ages (or at least within the last one), temperate and severe periods occur. The colder periods are called ‘glacial periods’, the warmer periods ‘interglacials’.
During the most recent North American glaciation, the Wisconsin glaciation (70,000 to 10,000 years ago), ice sheets extended to about 45 degrees north latitude.
This Wisconsinian glaciation left widespread impacts on the North American landscape. The Great Lakes and the Finger Lakes were carved by ice deepening old valleys. Most of the lakes in Minnesota and Wisconsin were gouged out by glaciers and later filled with glacial meltwaters.
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