9) Petrified Forest, Calistoga, Napa Valley
Home to the largest petrified trees in the world, it’s the only one of its kind in California. The main trail runs just under a half mile. You can take a self-guided tour or go with a guide. The Meadow Walk trail will lead you to view the site of the volcano which petrified the trees when the volcanic explosion occurred 3.4 million years ago. So, walking on the felled trees can be quite an experience, albeit even a little bit creepy. The extinct volcano is what we now know as Mt. Helena. Its powerful blast knocked down all the Redwood trees and buried them in volcanic ash. The lack of oxygen caused them to petrify, since nothing could decompose. Thousands of years following saw the formation of mineral rich water in the area. As the water traveled through the felled trees, the mineral deposits preserved every detail.