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Safety Tips

The Chumash Trail

By Mike Kuhn


The Chumash Trail is approximately 2.5 miles in length, extending from the northern end of Flanagan Drive to the top of the ridge 1.3 miles north of Rocky Peak. To get to the trailhead, take Yosemite Avenue north from the 118 (Ronald Reagan) Freeway in Simi Valley. Flanagan Drive is the first right turn north of Alamo Street. Flanagan Drive forms the western boundary of the Chumash Natural Park, which includes beautiful sandstone rock formations, complete with caves. To access the trail, park along the eastern side of Flanagan Drive as close to the northern end as possible.

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


The Chumash Trail begins in a clayey shale and siltstone, with some interbedding of sandstone strata of the Santa Susana Formation. This formation is marine and of the Paleocene Epoch and was deposited roughly 60-64 million years ago. The formation is made up largely of turbidites, which were deposited at depths by turbidity currents, in the form of submarine slides from the continental shelf into the depths of the ocean. After the first quarter of a mile up the mountain at the first level area, a wide stratum of large cobbles is encountered, which is the Simi Conglomerate of the Santa Susana Formation. The Simi Conglomerate at this location is marine and was deposited as submarine fanglomerates at the mouths of a deep sea canyon. Still further up the trail are some large sandstone outcroppings at the headwaters of the White Oak drainage. The sandstone includes caves and is also part of the Santa Susana Formation. After crossing the sandstone stratum, you will again cross a wide zone of the Simi Conglomerates. Watch your step there, especially on the way down. The rounded cobbles are a bit like walking on marbles.

Within the next half mile the Chatsworth Formation is entered. That formation continues to the top of the ridges. The Chatsworth Formation is composed primarily of light gray, fine-to medium-grained sandstone. The sandstone, when exposed to air for many years, weathers to a tan color as a result of the oxidation of iron-rich minerals. The sandstone strata range from a few feet to 20-30 feet thick. Occasional beds of siltstone and cobbles are present on the western margins. The formation was deposited in the deep ocean, at a depth of 4,000-5,000 feet, by turbidity currents. Those turbidity currents were often a half mile or more in width and tens of miles in length. As a result, few fossils survived the grinding action of the long journey into the ocean depths. Some fossils, in the form of organic debris, are present along the trail beyond Hamilton Saddle (See map). In between these 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 out to sea from heavy runoff from the land. Those fines became the siltstone strata.

The formation is part of the North Pacific Plate, which is moving to the 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 locally tilted to the west by 25-45 degrees.

Once one tops the ridge at the trail's intersection with the Rocky Peak trail, you may wish to head north on the Rocky Peak trail a few hundred feet to the beginning of the next road cut. The southern branch of the Simi-Santa Rosa fault crosses the ridge at that point. Offset beds and shattered bedrock mark the fault.


The Chumash Trail begins in grasslands, moves quickly into coastal sage scrub and finally into chaparral plant community. The grasslands are made up primarily of introduced grasses from the Mediterranean Basin. Those annual grasses, which die each late spring and dry up, have displaced the perennial grasses that dominated our grasslands before the coming of the Spanish. These grasslands include coast live oaks and valley oaks. The grasses include:

  • ripgut and red bromes
  • foxtail
  • wild oats
  • soft chess
among others. Other plants include:
  • Mediterranean and black mustards
  • yellow star thistle
  • sweet fennel
  • laurel sumac
  • prickly lettuce
The coastal sage scrub includes:
  • black and white sages
  • California sagebrush
  • California buckwheat
  • purple nightshade
  • giant rye (California's largest native grass)
  • purple needle grass
  • laurel sumac
  • sugar bush
  • cudweed aster
  • California everlasting
  • yucca
  • yerba santa
  • Mediterranean and other mustards
  • deerweed
  • golden yarrow
  • soap plant
  • star lily
  • California peony
  • bush mallow
and many perennial species. Of special note is the catalina mariposa lily, which blooms in the spring and is present in the grasslands, coastal sage scrub and the chaparral plant communities. The yellow mariposa and Plummer's mariposa lilies are also present.

The yucca was called ta’apu by the Ventureno Chumash, who named the premier village in the area after the plant. That village was located up Tapo Canyon and is the source of the name "Tapo." Tapo canyons, on both sides of the Santa Susana Mountains, were the trails to Ta’apu.

The chaparral grows at a higher elevation than the coastal sage scrub with the same exposure to the sun, on north-facing slopes. Characterized by evergreen shrubs with small hard leaves, chaparral is a fire climax vegetation, successfully resprouting from root crowns after fires. From mid-summer through late fall, mature chaparral is extremely dry and loaded with volatile hydrocarbon compounds. When ignited, especially during Santa Ana winds, devastating wildfires can result.

Some chaparral species found along the trail include:

  • chamise
  • hoary-leaved ceanothus
  • California mountain mahogany
  • yerba santa
  • toyon
  • hollyleaf cherry
  • redberry
  • laurel sumac
  • sugar bush
  • scrub oak
  • yellow bush monkey flower
  • Eastwood manzanita (near the top)
  • silk-tassel bush (also near the top)
  • Santa Susana tarplant
  • rose snapdragon
  • blue and scarlet larkspurs
  • golden yarrow
  • chia
  • large-flowered phacelia
  • caterpillar phacelia
  • woolly bluecurls
No poison oak is present along the trail.

The Santa Susana tarplant is the only plant with a local name. It is listed as "rare" by the state and is found in the rocky cave area above the White Oak drainage and in places along the last one-third of a mile from the top.


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

  • turkey vultures
  • red-tailed hawks
  • great-horned owls
  • poor-wills
  • California quail
  • mourning doves
  • Anna's hummingbirds
  • common flickers
  • scrub jays
  • mockingbirds
  • common crows
  • common ravens
  • towhees
  • white-crowned and English sparrows
reptiles, such as:
  • southern Pacific rattlesnakes
  • San Diego gopher snakes
  • California king snakes
  • San Diego/California homed lizards
  • San Diego alligator lizards
  • the western fence and California side-blotched lizards
mammals, such as:
  • rabbits
  • California ground squirrels
  • Botta's pocket gophers
  • agile kangaroo rats
  • deer mice
  • dusky woodrats
  • coyotes
  • ringtail cats
  • southern California weasels
  • striped skunks
  • mountain lions
  • bobcats
  • mule deer
While mountain lions are present in the hills around the valley, encounters are unlikely. Do not hike alone, and keep small children close at hand. Rattlesnakes may be encountered. Stay on the trail and avoid them. Be observant, and never try to handle them. Do not handle any wild animal, including bats, even if they appear to be injured.

The trail is on property owned by the Santa Monica Conservancy. The Chumash Trail was constructed between November 1989 and January 1990. The trail is maintained by the Rancho Simi Trail Blazers and patrolled by the Volunteer Trail Safety Service, which is a volunteer organization associated with the Rancho Simi Recreation and Park District. If you have any questions about either of these organizations, you can call the Volunteer Coordinator with the Rancho Simi Recreation and Park District at (805) 584-4453.