According to my admittedly dubious calculations, the oil drop depicted on the cover of this book would satisfy our current(actually 2005) oil consumption for over 7 million years.
1 mi = 5280 feet
1 cu foot = 7.48051948 US gallons
1 oil barrels = 42 US gallons
Total World Petroleum Consumption(2005) = 83,607,000 barrels/day
Surface area of Guatemala = 42,042 sq mi
Assumptions(here we go):
the drop looks about the size of the Central American country pictured in green near it. I think that’s Guatemala. I assumed that the drop has about as much volume as Guatemala if Guatemala were a box with (length * width) equal to Guatemala’s surface area and depth equal to Guatemala’s approximate east-west width (I figure it at about 200 mi).
So it’s a 200 mi by 42042 sq mi volume.
PHEW! That was easy.