Tectonic plates move slowly, propelled by seafloor spreading, causing fissures around ocean floors. The location of continents affects global climate, regulating ice ages and causing deserts. Antarctica was once a lush forest continent, and the supercontinent Pangea produced the largest desert ever.
According to the theory of plate tectonics, the tectonic plates that house the world’s continents move slowly relative to each other, only noticeably rearranging them on time scales of millions of years. Tectonic plates move at the same rate that fingernails grow. They are propelled by a phenomenon called seafloor spreading, in which the edges of oceanic plates are constantly being engulfed by the mantle, allowing new magma to rise to fill the cracks that form in the center of the plate. The fissures caused by seafloor spreading extend in a continuous line around the ocean floors of the world.
The location of continents affects global climate in several ways. The relative arrangement of continents may regulate the comings and goings of major ice ages more than solar cycles or any other factor. When there is a continent around the northern or southern polar regions, it is at risk of becoming frozen and impacting global climate. Especially in the case of Antarctica, which is exclusively polar, a frigid circumpolar current begins to circulate the continent and causes feedback cycles of cooling and glaciation. As a result, the interior of Antarctica is the largest desert in the world; desert is defined as the absence of moisture. The extremely low temperatures lock all the moisture into the ice.
Once, tens of millions of years ago, Antarctica was a lush forest continent. For most of the planet’s history, forests have stretched from pole to pole. Dinosaur fossils have been found within 20 degrees paleolatitude of the South Pole. This is especially remarkable considering that dinosaurs had slower metabolisms than mammals and probably couldn’t even cope with the cold. Their sensitivity to global weather is likely what contributed to their downfall. Their inability to deal with global climate change is what led to mammals surviving the mass extinction and death of dinosaurs (except the ancestors of birds).
Another factor that strongly influences global climate is whether continents are pushed together, as in the supercontinent Pangea, or largely separated, as is the case today. When the continents are together, it means that much of their land surface is far away from the oceans, making it difficult for moisture to reach them, producing deserts. The largest desert ever to exist is thought to have been the center of the continent Pangea. Life is abundant within most continents today, but then the center of Pangea would have been virtually devoid of all life.
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