Lead diffuses (or leaks) from zircon crystals at known rates that increase with temperature. Because these crystals are found at different depths in the Earth, those at greater depths and temperatures should have less lead. If the Earth’s crust is just a fraction of the age claimed by evolutionists, measurable differences in the lead content of zircons should exist in the top 4,000 meters. Instead, no measurable difference is found.a
Similar conclusions are reached based on the helium content in these same zircon crystals.b Because helium escapes so rapidly and so much helium is still in zircons, they (and Earth’s crust) must be less than 10,000 years old.c Furthermore, the radioactive decay that produced all that helium must have happened quite rapidly, because the helium is trapped in young zircons.