Yosemite activity and adventure holidays from the adventure travel experts at Exodus. Straddling the Sierra Nevada Mountain Range, Yosemite National Park consists of the most unusual formations. Being of volcanic origin, the Sierra’s geology consists almost entirely of granite. The last ice age’s massive glaciers sawed some of the huge granite domes in half, cutting deep valleys which are now mostly cloaked in forest. The park is a hiker’s paradise with numerous trails weaving their way through the dramatic scenery. There is a variety of interesting flora and fauna in the park, including black bears.