Geologists have just discovered the oldest terrestrial rock yet: some badly battered bit of something called a faux-amphibolite from Northern Quebec, Canada that has been dated to 4.28 billion years ago. I’m afraid most of the paper is way above my head — lots of radioisotope measurements, discussions of the details of the local geology, etc. — but I can at least note that this means Ken Ham is wrong by a factor of over 713,000. I am impressed by both the age of the rocks and the magnitude of the error a creationist can sustain without exploding into a cloud of pink pixie dust that fades to the sound of waning calliope music.
O’Neil J, Carlson RW, Francis D, Stevenson RK (2008) Neodymium-142 Evidence for Hadean Mafic Crust. Science 321(5897):1828-1831.