Radiogenic dating of meteorites
The nature of an unconformity can change with distance.Notice how if we are only examining a small area in the figure above, we would determine a different type of unconformity at each location, yet the unconformity itself was caused by the same erosional event.
Calculations in 1889 gave estimate for the age of the Earth of 90 million years.
Age of Earth estimated from time required to cool from an initially molten state.
Assumptions include, the initial temperature of the Earth when it formed, the present temperature throughout the interior of the Earth, and that there are no internal sources of heat.
We call such a break in the stratigraphic record a hiatus (a hiatus was identified in our trash pit example by the non-occurrence of the Ceramic Cups layer at the UNO site).
When we find evidence of a hiatus in the stratigraphic record we call it an unconformity.