Researchers from the University of Colorado at Boulder think they've found evidence that the very early Earth had continents soon after the planet formed, overturning theories that the planet was Moon-like, or covered with oceans. The team analyzed a rare element called hafnium in ancient minerals from the Jack Hills in Western Australia. It showed that continental crusts had formed 4.4 - 4.5 billion years ago, and were then recycled into the Earth's mantle.