[Chickensoup]

Jeff, search salt mine, then images

Some of the largest salt mines in the world are in the US.

[ProtectOurFreedom]

All the salt in those mines, caverns and domes was laid down long ago from seawater deposits. All salt has its origins in the sea. The oceans are powerful concentrators of salt.

There are an estimated 71 trillion tons of salt below the Great Lakes. Here's a salt mine tunnel 1,200 feet below downtown Detroit...