什么是 Glacial period; interglacial; glacial termination？

In the Quaternary record, a glacial period is an interval when large ice sheets cover the northern continents, recorded by high benthic $\delta^{18}$O and low sea level; an interglacial is an interval with little land ice in the Northern Hemisphere outside Greenland, like the present. A glacial termination is one of the major transitions that end a glacial cycle, from full glacial to interglacial conditions, much faster than the growth that preceded it.