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Quaternary glaciation also known as the Pleistocene glaciation or the current ice age, refers to a series of glacial events separated by interglacial events during the Quaternary period from 2.58 Ma (million years ago) to present.
During this period, permanent ice sheets were established in Antarctica and perhaps Greenland, and fluctuating ice sheets occurred elsewhere (for example, the Laurentide ice sheet). The major effects of the ice age are erosion and deposition of material over large parts of the continents, modification of river systems, creation of millions of lakes, changes in sea level, development of pluvial lakes far from the ice margins, isostatic adjustment of the crust, and abnormal winds. It affects oceans, flooding, and biological communities. The ice sheets themselves, by raising the albedo, effect a major feedback on climate cooling.
During the Quaternary Period, the total volume of land ice, sea level, and global temperature has fluctuated initially on 41,000- and more recently on 100,000-year time scales, as evidenced most clearly by ice cores for the past 800,000 years and marine sediment cores for the earlier period. Over the past 740,000 years there have been eight glacial cycles.
The entire Quaternary Period, starting 2.58 Ma, is referred to as an ice age because at least one permanent large ice sheet — Antarctica — has existed continuously. There is uncertainty over how much of Greenland was covered by ice during the previous and earlier interglacials. During the colder episodes — referred to as glacial periods — large ice sheets also existed in Europe, North America, and Siberia. The shorter and warmer intervals between glacials are referred to as interglacials.
During the glacial periods, the present (i.e. interglacial) hydrologic system was completely interrupted throughout large areas of the world and was considerably modified in others.
Due to the volume of ice on land, sea level was approximately 120 meters lower than present.
Evidence
The evidence of such an event in the recent past is robust. Over the last century, extensive field observations have provided evidence that continental glaciers covered large parts of Europe, North America, and Siberia. Maps of glacial features were compiled after many years of fieldwork by hundreds of geologists who mapped the location and orientation of drumlins, eskers, moraines, striations, and glacial stream channels. These maps revealed the extent of the ice sheets, the direction of flow, and the locations of systems of meltwater channels, and they allowed scientists to decipher a history of multiple advances and retreats of the ice. Even before the theory of worldwide glaciation was generally accepted, many observers recognized that more than a single advance and retreat of the ice had occurred. Extensive evidence now shows that a number of periods of growth and retreat of continental glaciers occurred during the ice age, called glacials and interglacials. The interglacial periods of warm climate are represented by buried soil profiles, peat beds, and lake and stream deposits separating the unsorted, unstratified deposits of glacial debris.
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Last Glacial Maximum
The Last Glacial Maximum (LGM) refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and Asia. These ice sheets profoundly impacted Earth's climate, causing drought, desertification, and a dramatic drop in sea levels. It was followed by the Late Glacial Maximum.
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Late Glacial Maximum
The Late Glacial Maximum (ca. 13,000-10,000 years ago), or Tardiglacial ("Late Glacial"), is defined primarily by climates in the northern hemisphere warming substantially, causing a process of accelerated deglaciation following the Last Glacial Maximum (ca. 25,000-13,000 years ago).
It is at this time that human populations, previously forced into refuge areas as a result of Last Glacial Maximum climatic conditions, gradually begin to repopulate the northern hemisphere's Eurasian landmass and eventually populate North America via Beringia for the first time.
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