The Previous Glacial Period

techtonic plates 

Pacific Ring of Fire

Extent of glacial Ice (grey) in the North and South acted like a vice grip squeezing down on the earths molten core.  In the The glaciers accumulated miles thick, its weight forcing the plates to sink beneath and then bowling upward along the ice free edges of the North American and Eurasian Plates.  The vice-like squeezing  resulted in lands near the equator to rise, and new islands emerge from the sea and oceans of the world... volcanic land masses.