7.4 Pleistocene glaciations and their impact on landscapes
5 min read•july 30, 2024
Pleistocene glaciations reshaped Earth's surface, leaving lasting marks on landscapes worldwide. Massive ice sheets advanced and retreated multiple times, driven by and climate feedbacks, carving valleys, depositing sediments, and altering sea levels.
These glacial cycles profoundly impacted global climate and ecosystems. The resulting landforms, from U-shaped valleys to drumlins and moraines, continue to influence modern topography, hydrology, and ecology, shaping the world we inhabit today.
Pleistocene Glaciations: Causes and Extent
Milankovitch Cycles and Climate Feedback
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spanned from approximately 2.6 million to 11,700 years ago characterized by multiple
Milankovitch cycles drove these climate fluctuations through variations in Earth's orbital parameters
Orbital eccentricity changes Earth's distance from the sun over a 100,000-year cycle
Axial tilt varies between 22.1° and 24.5° over a 41,000-year cycle affecting seasonal contrasts
Precession alters the orientation of Earth's axis over a 26,000-year cycle influencing which hemisphere faces the sun at perihelion
mechanisms amplified orbital forcing effects
Atmospheric CO2 concentrations decreased during glacial periods (180 ppm) and increased during interglacials (280 ppm)
Albedo effects from expanded reflected more solar radiation reinforcing cooling trends
Glacial-Interglacial Cycles and Global Ice Extent
occurred around 26,500 to 19,000 years ago marking peak ice sheet extent
Glacial-interglacial cycles typically lasted about 100,000 years
Interglacial periods were shorter lasting approximately 10,000-30,000 years
Pleistocene glaciations affected both hemispheres globally
North America ice sheets covered much of Canada and northern United States (Laurentide and Cordilleran ice sheets)
European ice sheets extended over Scandinavia and parts of the British Isles ()
Asian ice sheets covered parts of Siberia and the Tibetan Plateau