Blowing up rocks

You make an explosion on the top of the ground.  Shockwaves goes down into the ground and it bounces off one of the rocks in the ground and bounces back up to the top.  Then they can tell what the rocks look like underneath.  This is a seismograph.

Minecraft

I made a land of lava and it's name was called Lavaland.

Minecraft

I built a big house that was made out of bedrock.