noun
stadial; stade
Geological term for a cooler period within an interglacial, less severe than a full glacial period.
最終氷期の後、いくつかの亜氷期が訪れた。
After the last glacial period, several stadials occurred.
氷期 is a full glacial period, much colder and longer than a 亜氷期.
Compound of 亜 (a, 'sub-') + 氷期 (hyōki, 'glacial period'). The term is a modern geological coinage.