We spent the night in Twentynine Palms, just north of Joshua Tree Nat. Park and planned a desert backroad route up toward Death Valley. About 50mi. north of Twentynine Palms I had noticed a big black smudge on Google Earth: a lava flow with a hiking destination called Amboy Crater. http://www.blm.gov/ca/st/en/fo/needles/amboy.html
This turned out to be a pleasant walk, reminiscent of SP Crater above Flagstaff though less high and steep. There is a nice facility and trail maintained by BLM and its well worth a stop. The sound of explosions and machine gun fire from "nearby" Marine training adds to the excitement.
A campfire must be extinguished by drowning it with water, stirring with a shovel, and repeating that process until the campfire is cold to the touch. A campfire is still a danger if it has any trace of heat, and must not be left or abandoned. Wildfires can begin by abandoned campfires that rebuild heat on windy days and then blowing embers ignite surrounding grasses and brush.