Glacial periods, also known as ice ages, are times in Earth's history when large areas of the planet are covered by ice sheets and glaciers. These periods are characterized by significantly lower global temperatures, which can last for thousands to millions of years. During a glacial period, ice expands from polar regions toward lower latitudes, affecting climate, sea levels, and ecosystems. The most recent glacial period, known as the Quaternary glaciation, began around 2.58 million years ago and continues today, with alternating glacial and interglacial phases. During glacial phases, ice sheets, such as the Laurentide Ice Sheet in North America, can grow and retreat, shaping landscapes and influencing the distribution of plant and animal species.