Lava (properly called magma before it erupts) fills large underground chambers called magma chambers.

Radiometric dating assumptions video

There is also an exhaustive study of this subject called the (Radioisotopes and the Age of the Earth) Group, a team of six scientists who are investigating the subject in depth, and have published the first of several studies. Carbon-14 dating has limited value for evolution because its half-life is too short.

The method assumes that the production of Carbon-14 in the atmosphere from nitrogen is a process that is in equilibrium, and it is not. Sedimentary rocks normally cannot be dated with radiometric methods (there are a few exceptions) because they do not have crystals that were consolidated at the time the rock was formed.

These assumptions are: (1) the radioactive element decays at a constant rate (2) the rock crystal being analyzed is not contaminated by infusion of excess end product (3) the rock crystal contained no end product when it was formed (4) leaching of the parent element out of the rock sample did not occur.

The Potassium-Argon dating method suffers from both leaching and contamination problems.

Leaching of the parent element out of the rock would increase the age of a K-Ar sample.

One way to test this would be to analyze the sample before and after soaking it under pouring water.

The general idea is that many different minerals are formed, which differ from one another in composition, even though they come from the same magma.

The mineral makeup of an igneous rock is ultimately determined by the chemical composition of the magma from which it crystallized.

Lava erupting earlier would come from the top of the magma chamber, and lava erupting later would come from lower down.

A number of processes could cause the parent substance to be depleted at the top of the magma chamber, or the daughter product to be enriched, both of which would cause the lava erupting earlier to appear very old according to radiometric dating, and lava erupting later to appear younger.

Therefore, since sedimentary rock is the only kind of rock that bears fossils, a relative date is estimated by the position of a sedimentary rock in relation to an igneous outflow.