So, let's assume that the world flooded during the Great Flood. What does that  mean? Well, among other things, it means that all the glaciers floated away, including Antarctica. Thus, if you want to find the age of the world, all you need to do is count layers in the ice sheets, and you should know exactly when God flooded the world.

Simple, right?

So, if we go to Antarctica and drill down 800,000 layers, we get a problem. Noah clearly did not live 800,000 years ago.

So maybe it snowed more back then or different? Maybe, but is it "different" enough for the layers to be off by two orders of magnitude? Not likely. I'll gullibly accept whatever bad explanation you give me for extra layers, but I'm just not gullible enough to accept 100 layers per year. So, by beginning with the idea of believing in the flood, I come to the conclusion that the world is AT LEAST 800,000 years old.