Those look like they are covered in the writing of the Havasupais, the Native American tribe that lives in the Grand Canyon.
Yours looks like it comes from a Native American tribe from the San Francisco area called the hippais
Might be from a tribe of Railians. They cover the yard in their petroglyphs overnight. The Rapo-po tribe is in a constant battle with them for infringing on tribal lands and defacing their religious artifacts.