It is not for blasting the rock .
The Hole represents a Cave , perhaps sealed entrance , the signs left by the ancients , are all easy to decipher , if we do not try to over think them .
Real simple , the Ancients used the elements of Nature to convey messages . a Hole done in that style is a Cave .
The intent of the Two Hand set Boulders ?
Go up and peek around , obvious Man set , they're saying something for a fact .
watch for carved in stone figures ( Petroglyphs ) faint lines of petroglyphs .