â ãåîëîãèè - êðóïíûé èíòåðâàë ãåîëîãè÷åñêîãî âðåìåíè, â òå÷åíèåêîòîðîãî îáðàçîâàëèñü ãîðíûå ïîðîäû, ñîñòàâëÿþùèå ãåîëîãè÷åñêóþ ñèñòåìó.Ïåðèîäû ðàçäåëÿþòñÿ íà ãåîëîãè÷åñêèå ýïîõè.
