To give you an idea,,, when people put fence posts in they need to rent a jack hammer to make the holes.
There are two types of lava,, one is very hard and the other fairly soft, you never knowwhat kind you will deal with and it can be a mix ina small area.
When people buy a raw lot,, the hire a guy with a CAT D9 that has a giant rock breaking claw on it. They call it ripping a lot. The D9 just goes back and forth over the area and rips the lava into gravel. You end up with a flat lot that is black lava gravel...
here is a video of D9 ripping a lot,