Pinnacles National MonumentOffering rugged hiking trails, it protects a wilderness area containing the remains of half of a long-extinct volcano.
Chiricahua National MonumentAn enormous collection of weirdly-shaped rock pinnacles, remnants of a huge volcanic eruption about 25 million years ago, cover the higher regions of the park.
Devils Tower National MonumentThe tower is actually the core of an ancient volcano, rising over 500 feet into the air, with an aspect of columns given by hardened cooled magma.