By Jonah Fisher
Learn about where rocks come from, how fossils form and what is in soil.
The deepest hole humankind ever dug only got one thousandth of the way through the earth. But what would happen if you kept digging?
By Chloe Blissett
BBC Wales young reporter
By Dan Johnson
La Palma, Spain
The 112m-deep pit has long been shunned by many local people, who believe it harbours genies.