Pinnacles National Monument

Moses Spring Trail

EFFORT Minimal
LENGTH2.0 miles
GEOLOGICAL FEATURE(S)Fault Activity, Erosional Features, Caves
LOCATIONPinnacles National Monument
TRAILHEAD COORDINATES 36.28.737N, 121.10.977W

Description: Pinnacles National Monument is a little different from most parks. The park road does not go through from one side to the other, so you have to choose which entrance you want for the day. If you have the inclination, you can walk about four miles between the Bear Gulch Visitor Center on the east side and the Chaparral Entrance on the west side.

The two sides are like twin parks or parallel universes. They both have lots of amusing boulders and a set of caves. They both have a peaks trail, a wilderness trail, and a canyon trail. They both have visitor centers and approximately the same flora, fauna, and geology. But they also have differences. There is more surface water on the east side where our trail will turn up a natural spring and a reservoir. On the west side, there are more dramatic cliffs.

The "pinnacles" are the weathered remnants of an ancient volcano that used to be located in the Mojave Desert about 200 miles away. Over the last 23 million years, the pinnacles have been traveling north from Southern California to their current position, as the Pacific Plate moved along the San Andreas Fault. A similar phenomenon has been described at Bodega Bay, where the granite rocks of Bodega Head are in no way related to the Franciscan Complex on the east side of the San Andreas Fault. These granites are similar in composition to rocks found far to the south in the Tehachapi Mountains or even Baja California. Anomalies like the Pinnacles and Bodega Head are some of the most observable evidence we have for the speed and direction of plate movement along this dynamic boundary. Today, the monument is moving an average of one inch per year northward.

(Photo courtesy of the National Park Service)

The result of this extraordinary activity is an area of intriguing rock formations for all levels of hikers to marvel at. Geologists theorize that this mountain once stood nearly a mile higher than 3,304-foot high North Chalone Peak, the highest point in the park today. Long-term erosion has broken it down to the craggy surface features which remain. Some day, even less of the old volcano will have moved on up north. The original bedrock here was granite. Look closely and you may see pieces of the granite caught up in the overlying rhyolite, as xenoliths. Also look for a light green pumice tuff, formed from volcanic ash separating the granite from the rhyolite and occurring sporadically elsewhere. In the park are examples of several volcanic rock types, including perlite (a rhyolitic volcanic glass), rhyolite, dacite, and andesite. About 60 percent of the rocks in the monument are breccia, a conglomerate of chunks of rhyolite which can be clearly seen embedded in the mass.

Even on this easy hike, make sure you bring water, especially in summer, and be prepared for cave temperatures between 50 to 60 degrees, regardless of the outside temperature. Bring flashlights to explore the water-sculpted caves, the most visited attraction at Pinnacles. This area floods during heavy rains, so the trail is not always open.

From the parking area, find the trailhead for Moses Spring Trail to the south. At a fork at 0.2 miles, the High Peaks Trail heads off to the right. We will be going left and looping back around to this junction.

You will walk along a creek and on some moss-covered stones, which can be slippery. The most likely wildlife you will see will be lizards scampering over the rocks, but there are rattlesnakes, bobcats, and even mountain lions in the park. We saw none of these predators. Trees near the water sources include live oak, buckeye, and sycamore. Blue oaks grow on hillsides, and in the drier areas, you will find chaparral plants like chamise, buckbrush, and manzanita.

After passing into the Little Pinnacles area, you will go through the caves on Bear Gulch Cave Trail, leaving Moses Spring Trail, which runs alongside the caves. The Bear Gulch Cave is 0.4 miles long, and not technically a cave, but rather a pocket created in a canyon where rocks have fallen and enclosed spaces beneath them. There is a bit of rock climbing required, but it is easily accomplished by most folks. If itís early spring, water will be dripping down the walls along this trail. Look for frogs and bats in the caves. The bats will begin to stir at dusk.

After exploring the cave, emerge on a path to Bear Gulch Reservoir, which is the far point of the trail and a spot to consider having lunch. You can choose to return the same way you came out for a 1.8-mile hike, or catch the Chalone Peak Trail on its way north from here to make a 2-mile loop. You can also stay on Moses Spring Trail on the return, avoiding the caves, and passing beside Moses Spring. If you take Chalone Peak Trail back, head north on it to a junction with High Peaks Trail and turn right. Make your way 0.3 miles further to the previously encountered junction, and turn left to reach the trailhead.

Driving Directions:For this hike, you will want to enter the park at the east entrance. There is no road linking the east and west entrances of the park. From King City on U.S. 101, take the First Street exit, heading east. Turn onto Highway G13/Bitterwater Road, and go 15 miles to Highway 25. Go 14 miles to Highway 146 West, and proceed 5 miles to the Bear Gulch Visitor Center, and then to the end of the road to the trailhead. There is an entrance fee.

Return to Trails Index