

There’s an area in the cascade range (western US, specifically oregon) that is a giant field of knapped obsidian, that was used as a training ground for young knappers, as well as a trading ground to trade knapped obsidian that has been found all over the western US. Not just miles, but many many miles. I’ll see if I can go find a link.
Most likely for performing maintainence on a vehicle without having to lift it with a jack. For simpler stuff like changing oil it can be easier to just use a couple of ramps instead of a jack and jackstands.