We first visited this site in 1998. We stopped by a few times since then but didn’t photograph the site again until 2009 when I wanted to get a few more photos than in my earlier visits. This is an interesting (and large) site and worth the visit.
Most of the designs here are abstract and probably from the Desert Archaic culture.
The lava flows make a natural tank here that would have held rainwater for a long period of time. A vital resource in an area without many springs.