Unlike the Moon our dead, rocky companion the Earth is alive, pulsing with creative and destructive forces that power its geological metabolism. Lunar rocks brought back by the Apollo astronauts all date back to about the age of the Solar System. Moon rocks are forever. Earth rocks, on the other hand, face the perils of a living lithosphere. All will suffer ruination, through some combination of mutilation, compression, folding, tearing, scorching and baking. Thus, the volumes of Earth history are incomplete and disheveled. The library is vast and magnificent but decrepit. And it was this tattered complexity in the rock record that obscured its meaning until relatively recently. Nature provided no card catalog for geologists this would have to be invented. Five thousand years after the Sumerians learned to record their thoughts on clay tablets, the Earth's volumes remained inscrutable to humans. We were geologically illiterate, unaware of the antiquity of our own planet and ignorant of our connection to deep time. It wasn't until the turn of the 19th century that our blinders were removed