Glacial period
A glacial period marks an interval of time spanning thousands of years within a larger ice age. During these intervals, temperatures drop significantly and glaciers advance across the landscape. Interglacials represent the warmer periods that exist between these cold phases. The current interglacial era is known as the Holocene. A planet with no glaciers on its surface enters what scientists call a greenhouse climate state.
The Quaternary period began approximately 2.6 million years before present. Within this timeframe, at least eight distinct glacial cycles have occurred in the last 740,000 years alone. Changes in atmospheric carbon dioxide levels served as primary drivers for globally cold climates during glacials. Warm interglacials were influenced by shifts in ocean physical circulation patterns. Biological productivity and seawater acid-base chemistry likely caused most recorded changes throughout this history.
The Penultimate Glacial Period started about 194,000 years ago and concluded 135,000 years ago. This phase ended with the beginning of the Eemian interglacial. The Last Glacial Period followed, starting around 110,000 years ago and ending roughly 11,700 years ago. Over the last 650,000 years, there have been on average seven cycles of glacial advance and retreat. These cycles define the recent geological history of Earth's ice ages.
Glaciations during the Last Glacial Maximum reached their peak extent about 26,500 BP. In North America, these ice sheets carried the name Wisconsin. Great Britain experienced a period known as Devensian while Ireland faced the Midlandian phase. The Alps saw the Würm glaciation and northern Central Europe endured the Weichsel stage. East China hosted Dali glaciers while North China contained Beiye ice formations. Shaanxi province held Taibai glaciers and southwest Sichuan contained Luoji Shan ice. Northwest Sichuan featured Zagunao glaciers and the Tian Shan mountains held Tianchi ice. The Himalayas experienced Jomolungma glaciation and Chile saw Llanquihue ice sheets. In Europe, the ice sheet extended all the way to Northern Germany.
Changes in atmospheric carbon dioxide levels drove globally cold glacial climates throughout history. Orbital variations provided predictable patterns that computer models can now relate to climate possibilities. Ocean physical circulation shifts played a major role in causing recorded changes. Biological productivity within oceans also contributed significantly to these climatic cycles. Seawater acid-base chemistry likely caused most of the fluctuations seen over hundreds of thousands of years.
Computer models suggest the current warm climate may last another 50,000 years based on orbital variations. Work by Berger and Loutre indicates this duration is possible under normal conditions. However, greenhouse gases emitted into Earth's oceans and atmosphere may delay the next glacial period. This emission could push the start of the next ice age by an additional 50,000 years beyond natural predictions. These findings highlight how human activity alters long-term geological timelines.
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Common questions
What is a glacial period and how does it differ from an interglacial?
A glacial period marks an interval of time spanning thousands of years within a larger ice age where temperatures drop significantly and glaciers advance across the landscape. Interglacials represent the warmer periods that exist between these cold phases.
When did the Quaternary period begin and how many glacial cycles have occurred since then?
The Quaternary period began approximately 2.6 million years before present. Within this timeframe, at least eight distinct glacial cycles have occurred in the last 740,000 years alone.
How long did the Penultimate Glacial Period last and what followed it?
The Penultimate Glacial Period started about 194,000 years ago and concluded 135,000 years ago. This phase ended with the beginning of the Eemian interglacial.
Which specific names were given to ice sheets during the Last Glacial Maximum in different regions?
Glaciations during the Last Glacial Maximum reached their peak extent about 26,500 BP. In North America, these ice sheets carried the name Wisconsin while Great Britain experienced a period known as Devensian and Ireland faced the Midlandian phase.
What factors drive globally cold climates during glacial periods according to scientific models?
Changes in atmospheric carbon dioxide levels served as primary drivers for globally cold climates during glacials. Warm interglacials were influenced by shifts in ocean physical circulation patterns and biological productivity within oceans also contributed significantly to these climatic cycles.