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Rocky Peak Trail

By Mike Kuhn

THE TRAIL

The Rocky Peak Trail begins on the northern side of the 118 Freeway (Ronald Reagan Freeway) at the Rocky Peak Interchange. From the Simi Valley side, the Old Santa Susana Pass Road must be taken to the top of the pass.

We recommend a minimum of one quart of water, trail snacks, sunscreen, a hat, dark glasses and good hiking shoes. Dress for the weather.

The property is owned by the Santa Monica Mountains Conservancy. The trail is in the form of a fire road, which is broad and clear of vegetation. Rocky Peak is 2.5 miles from the trailhead and rises approximately 1,200 feet. The trail rises rapidly, with views of both the Simi and San Fernando Valleys. Some 6.8 miles from the trailhead, there is a "rock house" on the left for which stone and mortar were used to enclose a natural rock shelter. The rock house was built as part of a movie set. Across the road from the rock house is a natural cave above the road. The pictographs in the cave are modem. The Rocky Peak Road intersects the Hummingbird Trail a few hundred feet up the road. It is 2.3 miles from that point down the Hummingbird Trail to Kuehner Drive in Simi Valley. From the top of the trail, a side trail to the east extends approximately one quarter of a mile to a point overlooking both valleys. On the right side as one begins the trail to the east, is an old cistern that was used for fire fighting purposes before helicopters were used. The actual Rocky Peak is about 1,000 feet to the northeast. The top of the peak is the boundary between Los Angeles and Ventura counties. From the trail summit, it is 1.3 miles to the trail juncture with the Chumash Trail. The trail continues for approximately another 1.2 miles to another summit, which marks the end of the publicly-owned land. The hike from the trailhead is a 10-mile round trip.

This trail, along with the Hummingbird and Chumash trails, is very popular with mountain bikers. Hikers, bikers and equestrians should obey the rules of the trail and be courteous when in the presence of other users of the trail.

GEOLOGY

Most of the Rocky Peak Trail is located in the Chatsworth Formation, which is the name that geologists have given to the massive sandstone formations at the eastern end of Simi Valley. The formation is upper Cretaceous Period in age, dating from approximately 68 million years ago. At some point the Chatsworth Formation was lifted above sea level, and the upper portion of the formation was eroded away before new marine sediments were superimposed on the resulting landscape.

The Chatsworth Formation is composed primarily of light gray, fine-to-medium-grained sandstone strata, which are from a few feet to 20-30 feet in thickness. When exposed to air, the rock has weathered to a tan color. Occasional beds of siltstone and cobbles are present. The formation was deposited in the deep ocean, at a depth of 4,000 to 5,000 feet, by turbidity currents, i.e., massive submarine landslides, from the continental shelf into submarine canyons. Those turbidity currents were often a half-mile or more in width and ten or more miles long. As a result, few fossils survived the grinding action of the long journey into the ocean depths. In between those catastrophic events, there were quiet periods without turbidity currents when silt and clay particles mined down from the surface of the ocean as fines carried long distances into the ocean from heavy runoff from the land. Those fines became the siltstone strata.

The formation is part of the North Pacific Plate, which is moving northwest at a current rate of about 2.5 inches per year. Because of the collision with the North American Plate along the San Andreas Fault, the margin of the North Pacific Plate has been uplifted and tilted to the northwest from 2040 degrees.

There are many joints, vertical to the bedding plains, in the sandstone strata. Those joints, combined with the contacts between strata and cavernous weathering of the sandstone, have resulted in fascinating rock formations, including deep crevasses and cave formations.

The southern branch of the Simi-Santa Rosa fault cuts the ridge about 50 yards beyond the trail junction with the Chumash Trail. Evidence of faulting is very clear in the road cut on the eastern side of the road. Just beyond that point you move into the Simi Conglomerate Member of the Santa Susana Formation, which has an unconforming contact with the Chatsworth Formation. Very quickly you move into a dark gray clayey shale of the Santa Susana Formation. As you progress into Los Angeles County, near the top of the hill, you move into the much younger and fossiliferous Pico Formation. This formation is mostly soft, friable, nearly white, medium-to-coarse-grained sandstone with many bivalve shells, especially in hard calcareous reefs, and shell coquina, which were deposited in shallow marine lagoonal conditions.

PLANT LIFE

Two plant communities are present along the Rock Peak Trail. On the warmer and sunnier south-, southeast-and southwest-facing slopes, the plant life is composed primarily of coastal sage scrub species. Common species include:

  • California sagebrush
  • yucca
  • coyote brush
  • California brickellbush
  • Santa Susana tarplant
  • California buckwheat
  • ashyleaf buckwheat
  • deer weed
  • California dodder
  • giant rye
  • slender sunflowers
  • dove weed
  • yerba santa
  • golden yarrow
  • narrow-leaved bedstraw
  • California everlasting
  • bladderpod
  • silver lotus
  • horehound
  • wishbone bush
  • laurel sumac
  • sugar bush
  • black sage
  • purple nightshade
  • hollyleaf cherry
Many exotic naturalized annual grasses and weeds are present along with annual plants.

The chaparral occupies most north-facing slopes. That community is made up of evergreen shrubs with small, hard leaves. This fire climax vegetation is made up of plants which successfully resprout from the root crowns following brush fires. Characteristic plants include:

  • chamise
  • hoary-leafed ceanothus
  • California mountain mahogany
  • toyon
  • laurel sumac
  • bush monkey flower
  • hollyleaf redberry
  • poison oak
  • coast live oak
  • Eastwood manzanita
  • lance-leafed liveforever
  • Santa Susana tarplant
  • fuchsia-flowered gooseberry
Many of the coast sage scrub and the chaparral species occur in both communities.

Of special interest along the trail is the Santa Susana tarplant, which is a state-designated "rare" plant. It grows primarily out of the cracks in sandstone, and has a very limited range that is focused on the eastern end of Simi Valley, and other sites with massive sandstone. Just south of the rock house are bay laurel trees. The pungent leaves of the bay laurel are used in Italian cooking.

The yucca is also of special interest in that it has given us the name "Tapo." The Ventureno Chumash Indian village in Tapo Canyon was named for this plant and was called ta'apu. To the Indians the area around the village became "the Tapo" and the trail to ta'apu was Tapo Canyon.

The only hazardous plant on the trail is poison oak. Poison oak is present along only one short stretch about a quarter of a mile above the Hummingbird Trail junction. Avoid touching the plant, keep it off of your clothing, and keep your dog out of it if at all possible. The leaves are shinny and dark green and have three leaflets.

ANIMAL LIFE

Animals that may be observed along the trail include mainly birds, such as:

  • turkey vultures
  • red-tailed hawks
  • great-horned owls (Mostly at night)
  • California quail
  • rufous-sided and California towhees
  • mourning doves
  • crows
  • ravens
  • road runners
  • mockingbirds
  • whitecrowned sparrows
reptiles, such as:
  • southern Pacific rattlesnakes
  • two-striped garter snakes
  • gopher snakes
  • California king snakes
  • San Diego alligator lizards
  • Western fence lizards
  • homed lizards
mammals, such as:
  • rabbits
  • California ground squirrels
  • agile kangaroo rats
  • deer mice
  • dusky woodrats
  • coyotes
  • striped skunks
  • raccoons
  • mule deer
  • bobcats
  • mountain lions
While mountain lions are present in the hills and are occasionally seen by hikers and bikers, cncounters are unlikely. Do not hike alone and keep small children close at hand. Rattlcsnakes may be encountered at any time. Stay on the trails and avoid them when they are encountered, be observant and never try to handle them. Do not handle any wild animal, including bats, even if they appear to be injured.