From WordNet (r) 2.0 (August 2003) [wn]:
geological
adj : of or relating to or based on geology; "geological
formations"; "geologic forces" [syn: geologic]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Geologic \Ge`o*log"ic\, Geological \Ge`o*log"ic*al\, a. [Cf. F.
g['e]ologique.]
Of or pertaining to geology, or the science of the earth.
[1913 Webster]