Job 5:9

Which doeth great things and unsearchable; marvellous things without number:

God does great things that are unsearchable, and marvelous things too many to count. Applied to creation, this means His creative work cannot be fully comprehended by human reasoning, remaining beyond human understanding and searching. He has not revealed every detail of how He accomplished creation. In particular, He has not revealed to mortals exactly how He made the world in six literal days, so that manner of working remains incomprehensible. The Scriptural history of the Flood is given to explain mysteries about the earth that geology alone cannot fathom.