It seems like the easiest way would be if you hit immutable lava at some point.
Minecraft solves the issue by making the bottom layer of its maps a special kind of block ('bedrock') that cannot be broken with any tool in the game without use of admin-level commands or the 'creative' mode.
Just like in real life. Wait a sec...
Minecraft solves the issue by making the bottom layer of its maps a special kind of block ('bedrock') that cannot be broken with any tool in the game without use of admin-level commands or the 'creative' mode.