The Earth’s surface is like a jigsaw puzzle. It is made up of many huge plates, or pieces, which slide very slowly around the globe. The continents lie atop these tectonic plates, as you can see in the image above, in which the purple lines show where the edges of the plates are. Where these plates come together or diverge, earthquakes and mountain building, among other things, can occur. Plate movement is driven by the Earth’s internal heat. The position of a plate, and of any continents that might be one top of it, is one determiner of whether that continent will experience glaciation. For example, if the plate which holds North America and Greenland were shifted a bit, North America could be covered in a continental ice sheet right now. Instead, Greenland is, because that is how the plates sit at present. Plate movement also affects the climate because CO2 escapes to the ocean and atmosphere where plates meet. When two plates converge (come together), volcanoes often result, which expel CO2 into the atmosphere when they erupt. When plates diverge (move apart), also known as seafloor spreading, hot magma is often released directly into the ocean, bringing CO2 with it.