Breaking big rocks into little rocks

Not really, but some how over the years there migrated a few hundred pounds of cement and limestone into the yard. It was such a nice day today that I lit the rockets on the car and flew home to start a bit of yard work. Some PO planted Junipers and then ringed the area with the "stones".
The first pic is the area and the last is all the rocks I pulled out. The Honda is there for scale. Or is it the rocks are there for scale?