Geologic timespan (3)
I believe the answer is:
eon
(Other definitions for eon that I've seen before include "Geological period" , "Era" , "An immense time" , "thousand million years" , "Vast age (alt. sp.)" .)
I believe the answer is:
eon
(Other definitions for eon that I've seen before include "Geological period" , "Era" , "An immense time" , "thousand million years" , "Vast age (alt. sp.)" .)