Started a world. Everything looks good on the surface.

Dug into a hill. after a few blocks, nothing but stone. Dug diagonally down all the way to bedrock. nothing but stone until bedrock. no caves encountered. All solid. Dug horizontally from layer ~12 ~100 blocks. nothing but stone and no caves. staired back up, just stone until almost the surface. Looked around. found a cave that started from the surface. went down a little way. Dug in a little bit. lots more stone.

Very strange.