Failed carbon dating
Figure 19.5, curve C, shows the dipole field strength calculated from measurements of magnetism of lava flows and of artifacts such as pottery and bricks, whose age can be determined.The curve is roughly fitted to mean values determined about every 500 to 1,000 years...Sometimes it slows down to a trickle so that much more water is leaking out the barrel than is coming in; sometimes it goes full blast so that a lot more water is coming into the barrel than is leaking out. Lingenfelter's paper was written in 1963, before the cycles of C-14 variation we described had been fully documented.
Thus, he concluded, if our Earth were older than 30,000 years the incoming water should just equal the water leaking out.
Creationists don't want their readers to be distracted with problems like that -- unless the cat is already out of the bag and something has to be said.