However, research by geologist John Woodmorappe (a pen name) revealed that the radiometric methods used today were actually hand-picked to coincide with the dates previously assumed for the geologic column diagrams.
These dating methods rely on a series of assumptions about the amounts of the parent-daughter elements, and a constant rate of decay. It has been accepted that a rock is formed when it first cools down from a molten or semi-molten state, which may include a variety of elements, including radioactive ones. For the last 100 years we have been able to measure the decay rate, and during this time it has been very steady, very consistent.
In fact, the very concept of strata representing long ages does not come from the rock strata themselves.
Helens dacite: The failure of Austin and Swenson to recognize obviously ancient minerals.
A Summary of the Million Dollar RATE Research Project (Radioisotopes and the Age of The Earth) Introduction: Rocks and fossils do not come with dates on them.
This is despite the fact that it causes more problems for interpreting rock strata than it solves.
And today we know through lab experiments and natural disasters (such as the eruption of Mt. Helens) that major layering of rock strata can happen catastrophically in a short period of time.
The conventional K-Ar dating method was applied to the 1986 dacite flow from the new lava dome at Mount St. The whole-rock age was 0.35 /- 0.05 million years (Mya). Excess argon within mineral concentrates from the New Dacite Lava Dome at Mount St. Creation Ex Nihilo Technical Journal 10(3): 335-343. module=research&action=index&page=researchp_sa_r01 Henke, Kevin R.