glazialen

Glazialen are periods within Earth's climatic history marked by the advance of large ice sheets and generally cooler global temperatures. They are the counterpart to interglacial periods, during which ice sheets retreat and climates warm.

In the Pleistocene epoch, glazialen occurred repeatedly, producing cycles of advance and retreat of ice across the continents. Regional stage names, such as Würm in the Alps, Weichselian in northern Europe, and Wisconsin in North America, are often used to describe these events; globally, the Last Glacial Maximum is the best known phase, roughly 26,500 to 19,000 years ago.

Evidence for glazialen includes moraines, drumlins, and glacial till left by retreating ice; outwash plains formed by meltwater; varved lake sediments; and isotopic records from ice cores and marine sediments that track temperature and precipitation. These periods also coincide with lower sea levels and shifts in ecosystems and human populations.

Glazialen are driven by orbital variations identified as Milankovitch cycles, which alter insolation over tens of thousands of years. Feedbacks such as increased surface albedo from ice, changes in greenhouse gas concentrations, and shifts in vegetation reinforce cooling and ice-sheet growth.

In modern science, glazialen help interpret climate history and landscape formation. The current Holocene interglacial is the ongoing period between glazial phases, and ongoing research seeks to understand how natural cycles interact with human-driven climate change.