Moving extremely slowly like a glacier, or relating to ice and frozen periods in Earth's history.
From Latin 'glacialis' meaning icy, derived from 'glacies' (ice). The word entered English in the 17th century to describe the geological periods when ice sheets covered large parts of Earth.
Glacial pace became famous through Carl Sagan's discussions of deep time—when geologists talk about glacial movement, they mean something so slow that a glacier might move only inches per year, yet it can carve entire valleys!
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