The Monument is divided by the rock formations into East and West Divisions, connected by trails. The east side has shade and water, the west has high walls. The rock formations provide for spectacular 'pinnacles' that attract rock climbers. It is popular with advanced rock climbers because of the many difficult and challenging climbs. The Monument is most often visited in spring or fall because of the intense heat during the summer months.
Pinnacles NM lies about 40 miles (64 km) inland from the Pacific Ocean and about 80 miles (128 km) south of the San Francisco Bay Area. The monument is in the southern portion of the Gabilan Mountains, part of California's Central Coast Range.
Elevation within the boundaries range from 824 ft (251 m) to 3,304 ft (1007 m) at the peak of North Chalone Peak.
The climate is Mediterranean, typical on the Southern and Central California coast. The Santa Lucia Mountains lie between the Monument and Pacific Ocean, blocking much of the moderating influence of the Ocean. In comparison to the nearby coast, temperatures have a daily larger range that can be 50 to 100 °F (10 to 38 °C). The average rainfall is 16 in (400 mm) per year. Snow can fall in small amounts at higher elevations between mid-December and January.
The vegetation is predominantly chaparral (about 80% of the Monument) with woodlands, riparian and grasslands merged into the chaparral. The diversity of intersecting ecosystems and altitude has led to great number of animal species that call the Monument home.
The Monument is located near the San Andreas Fault which had a hand in creating the unique formations the Monument protects. The Pinnacles are part of the Neenach Volcano which erupted 23 million years ago near what is Lancaster, California today. The movement of the Pacific Plate along the San Andreas Fault split a section of rock off from the main body of the volcano and moved it 195 miles (314 km) to the northwest. It is believed that the pinnacles came from this particular volcano due to the unique breccias that are only found elsewhere in the Neenach Volcano formations. Differential erosion and weathering of the exposed rock created the Pinnacles that are seen today.
Large scale earth movement also created the talus caves that can be found in the Monument. Deep, narrow gorges and shear fractures were transformed into caves by large chunks of rock falling from above and wedging into the cracks leaving an open area below.
Since the Pinnacles were moved to this area, the San Andreas Fault has moved 4 miles (6 km) to the East of the Monument. The original location of the San Andreas can be seen in the location of a current fault, the Chalone Creek Fault. Two other large faults are known to run through the Monument, the Miner's Gulch and Pinnacles Faults. These faults parallel the San Andreas and were most likely caused major movements of the master fault.
Seismic activity is frequent in the Monument and United States Geological Survey maintains two seismometers within the boundaries. Evidence of past and ongoing seismic activity can be seen in offset streams where they cross faults. Valley bottoms and terraces show signs of uplift.
There are several trails for day hikers, some of which are strenuous. The trails provide views of the surrounding hills and valleys on clear days. The San Andreas Fault is visible from some vantages along the trails.