BBHomestead - This area - I call it my high meadow - I would like to think there is a fairly deep soil cover. My entire 80 acres, including the two lakes, sits on top of the hardest basaltic lava fields this side of the Mississippi. In fact, it sits on top of many, many lava flows. I have never dug a hole up there. My entire property is in an area called the Channeled Scablands. The Channeled Scablands form the northern cap on the great wheat area - the Palouse.
It's all a part of the story of the great outflows from ancient Lake Missoula.
Originally, we had considered building our home up on the high meadow. Wind power. But there were too many down sides. Power would have had to be run all the way across the property. The almost constant wind would get old. The mile long driveway would have to be extended an extra half mile. Getting water, via a well, would have been questionable. And the dust & volcanic ash. I get enough right where the house is now. And the current house location is in a very sheltered area - on the Far East side of the property. A couple time a year it will blow so very hard the air will turn grey and I can not see my little lake. It's just 75 feet off my front deck. Normally, you will not see the dust or ash - except on all the furniture, etc in the house and on all the vehicles. Ha, ha - my teeth are alway shiny and clean. Volcanic ash will do that.
I have found that it's best to cultivate, disk, rototill to a quite shallow depth. Go deep and up come the rocks.
The old homesteads in this area did the best they could with what they had - lots of rock. House foundations, barn & outbuilding foundations, rock gabions for the fences, rock terracing. And perhaps - the low stone wall was to divert runoff from that cleared field.