I assumed the average thickness of the Earth's crust (the geological column) to be ten klicks. I subtracted the volume of a sphere 12,780 km in diameter from the volume of a sphere 12,800 km in diameter.
Dunno, it just seemed the right way to answer such an odd question.
How many cubic kilometers do you think have been exposed and analyzed by geologic methods and study? Not an easy question. How much is exposed and analysed in a day? Figure one cubic kilometer. Tons of potential fossils. How many days would it take to expose and analyze 10% of the supposed geologic column? 51,406,314 days. A little more than 140,839 years.
With these kinds of numbers, how justified are we in assuming a geologic "column" even exists, that is to say, a record that shows continuity from top to bottom throughout?