Thanks to the pioneering work of researchers such as William Smith, geologists in the early 1800s were able to swiftly organize rock formations into a single colossal record of Earth's history. Many geologists saw in this record a stormy epic, one in which our planet had been convulsed repeatedly by abrupt changes.
In European countries, the capacity of the common keg size is 13.21 gallons. It stands 20.94 inches high, the diameter of which is 16.06 inches. Aside from this, the next keg size has a capacity of 7.93 gallons. It has the same diameter as the 13.21-gallon keg, but it has a slightly lower height of 14.37 inches.
Generally a keg is a vessel smaller than a barrel; thus, it is 30 gallons or smaller. In the U.S. the terms half-barrel and quarter-barrel are derived from the U.S. beer barrel, legally defined as being equal to 31 U.S. gallons (this is not the same volume as some other units also known as barrels).