Jäätikköjaksojen

Jäätikköjaksojen, or glacial periods, refer to extended intervals of time in Earth's history characterized by a significant reduction in global temperatures, leading to the formation and expansion of continental ice sheets and alpine glaciers. These periods are part of larger glacial-interglacial cycles, where colder glacial periods are interspersed with warmer interglacial periods, such as the one we are currently experiencing.

The primary driver of glacial periods is believed to be fluctuations in Earth's orbital parameters, known as Milankovitch cycles. These cycles involve changes in the eccentricity of Earth's orbit, the axial tilt (obliquity), and the precession of the equinoxes. These variations subtly alter the amount and distribution of solar radiation reaching different parts of the planet, influencing long-term climate patterns. Other factors, such as atmospheric greenhouse gas concentrations and ocean circulation patterns, also play a role in modulating the intensity and duration of glacial periods.

During glacial periods, vast ice sheets can cover significant portions of continents, particularly in the Northern Hemisphere. This immense ice volume leads to a lowering of global sea levels as water is locked up in ice. The landscape is dramatically reshaped by glacial erosion and deposition, creating features like U-shaped valleys, fjords, moraines, and vast plains of glacial till. The climate during these periods is generally colder, drier, and characterized by more extreme weather events. The end of a glacial period, or deglaciation, occurs when global temperatures begin to rise, causing the ice sheets to melt and retreat, leading to a rise in sea levels.