The Earth has gone through multiple ice ages, periods when large ice sheets covered vast swathes of land. As you journey through this frigid timeline, you'll understand how these ice ages have shaped our planet and the life it hosts.
The Pleistocene epoch, the most recent ice age, began about 2.6 million years ago. During this time, the Earth was a battlefield for cycles of glaciation with warmer interglacial periods in between. The most recent glaciation period, often referred to as the "Ice Age", occurred 11,700 years ago, marking the start of the current Holocene epoch.
These ice ages have imprinted their cold fingers on our landscapes. The Great Lakes, the rolling plains of Canada, and the fjords of Norway are all relics of the ice age's mighty glaciers. Furthermore, the changing climates and landscapes influenced the evolution of life, leading to the extinction of megafauna and the rise of our ancestors, Homo sapiens.
But what causes these ice ages? One compelling theory involves Milankovitch cycles - long-term changes in Earth's orbit and tilt. These cycles affect the amount of sunlight reaching Earth, thereby influencing climate. Changes in the composition of Earth's atmosphere, particularly levels of greenhouse gases, also play a role.
Scientists study ice ages using a variety of methods. Ice cores, long cylinders drilled from ice sheets, provide a snapshot of past climates, while marine sediments reveal more about global temperature trends.
As you reflect on this chilling history, remember our current climate change predicament. While ice ages are a natural part of Earth's climate system, human activities are now driving unprecedented changes, the effects of which we are just beginning to understand.