Kylmäkausi

Kylmäkausi, often translated as "cold period" or "ice age," refers to a geological period of significantly reduced global temperatures, leading to the formation of extensive ice sheets and glaciers. These periods are characterized by a widespread decrease in average temperatures, which can persist for millions of years. While the term "ice age" is commonly used, it's important to distinguish between glacial periods, which are phases of intense glaciation within a larger ice age, and interglacial periods, which are warmer intervals between glaciations.

The Earth has experienced several major kylmäkausi throughout its history. The most recent one, the Pleistocene epoch, began about 2.6 million years ago and is still technically ongoing, though we are currently in an interglacial period. During the Pleistocene, massive ice sheets covered large parts of North America and Eurasia, dramatically shaping landscapes through erosion and deposition. The formation and retreat of these ice sheets caused significant fluctuations in sea levels.

The causes of kylmäkausi are complex and involve a combination of factors. These include variations in Earth's orbit (Milankovitch cycles), changes in atmospheric composition, such as lower greenhouse gas concentrations, and shifts in ocean currents that regulate heat distribution. The geological record, including ice cores and sediment layers, provides crucial evidence for understanding the timing and extent of past kylmäkausi.