They move very slowly, on the order of centimeters each year, but continuously, leading to an ever-changing configuration of continents and oceans.įurthermore, the plates move at different rates, and they pull away from each other (divergent boundary), slide under/over, or crash into, each other (convergent boundary), or slide past each other (transform boundary), all of which changes their size and shapes. Plates may contain oceanic crust (the land under the oceans) or continental crust (the landmass that forms the continents), and most current plates contain both. Over the course of the 20th century, scientists discovered that the surface of the earth (the crust) is not a single hard layer, like the outside of a ball, but instead consists of several large pieces, called tectonic plates (the lithosphere), that float on top of a semi-solid layer of molten rock (the asthenosphere) and move around the planet. The intersection of these many processes has resulted in a rather complex global climate history that is still being unraveled. Relatively shorter-scale fluctuations in the Earth's orbit around the sun, as well as shifts in atmospheric and ocean circulation patterns, fluctuations in the amount of atmospheric carbon dioxide, and even the occurrence of large volcanic eruptions also impact global climate patterns and contribute to rapid changes, on the order of hundreds to thousands of years, between warm and cold climates. These shifts occur over tens, or even hundreds, of millions of years. Processes that occur over very long time scales, such as the movement of continents around the earth's surface as well as continental uplift and mountain building, seem to correlate with the long-term shifts between 'hot house' and 'ice age' global climates.

Researchers have identified several different processes that contribute to global climate change on drastically different time scales - from decades to millions of years - and both the individual processes and their intersection at varying time scales appear to influence when and how climate changes, as well as the rate at which it changes. The question of why ice ages occur is extremely complex and continues to be a primary area of research by climate scientists in a variety of disciplines.

Ice Age: Continental Drift instaling