Subdivisions. The Ordovician is the second period of the Paleozoic era. The Ordovician began after the end of a series of extinction events known as the Ordovician-Silurian extinction events which ended around 488 mya.
As a state highpointer, Humphrey's Peak in Arizona was on my bucket list. The trailhead was easy to find. The trail itself was not well maintained and rather rocky, which wasn't too bad going up, but required a lot of caution descending to protect your knees.
The San Francisco Mountains were once a stratovolcano more than 16,000 feet high. They blew their top much like Mt St Helens leaving behind the top six highest points in Arizona. The mountains are well known to geologists because of their rich history and diverse amounts of volcanic rocks such as pumice.