Ar atoms are able to diffuse through and escape from molten magma because most crystals have melted and the atoms are no longer trapped.
Entrained argon—diffused argon that fails to escape from the magma—may again become trapped in crystals when magma cools to become solid rock again.
Ar (argon), the atom typically remains trapped within the lattice because it is larger than the spaces between the other atoms in a mineral crystal.
But it can escape into the surrounding region when the right conditions are met, such as change in pressure and/or temperature.
The ratio of the amount of K which was present at the beginning of the elapsed time period.
After the recrystallization of magma, more Ca being the most abundant isotope.Thus, the amount of calcium originally present is not known with enough accuracy to be able to measure the small increase produced by radioactive decay.