How many letters does the top answer for “of or pertaining to geology, or the science of the earth.” have?

The most common answer is geologic (8 letters).

Crossword clue: of or pertaining to geology, or the science of the earth.

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

geologic 8 letters web-def

of or relating to or based on geology

geological 10 letters web-def

of or relating to or based on geology

of or pertaining to the earth. 50% similar → tellural