Oh, Andy loved geology. I imagine it appealed to his meticulous nature. An ice age here, million years of mountain building there. Geology is the study of pressure and time. That's all it takes, really. Pressure, and time. That and a big damn poster. Like I said, in prison, a man will do almost anything to keep his mind occupied. Turns out Andy's favorite hobby was totin' his wall out into the exercise yard, a handful at a time. I guess after Tommy was killed, Andy decided he'd been here just about long enough.