Santa Rosa Island

source: billdeweyphoto.com

At 84 square miles in size, Santa Rosa Island is the second largest of California's eight Channel Islands. It is approximately 15 miles long by 10 miles wide and is located in Santa Barbara County. Santa Rosa Island is 26.5 miles from the nearest mainland, three miles east of San Miguel Island, and six miles west of Santa Cruz Island. From Santa Barbara Harbor, it is 30 nautical miles to Bechers Bay. Vail Peak, at 1589 feet in elevation, is the highest point on the island.

Santa Rosa was the second of the three islands granted into private ownership under Mexico’s rule of Alta California. In 1843, brothers Jose Antonio and Carlos Carrillo received Santa Rosa Island as a gift from Gov. Manuel Micheltorena. The island was used for ranching from the mid-19th century until 1998.

Flora and Fauna

About 36 different species of plants on Santa Rosa Island are endemic to the California Channel Islands.

There are four plants restricted to Santa Rosa Island: live-for-ever (Dudleya blochmanae insularis), manzanita (Arctostaphylos Confertiflora, gilia (Gilia tenuiflora hoffmannii), and the variety of Torrey pine (Pinus torreyana insularis).

Santa Rosa Island has poison oak (Toxicodendron diversilobum), Chaparral zygadene (Zygadenus fremontii), and several species of nightshade (Solanum sp.) each of which has some toxic properties.

 Jimson weed (Datura sp.) is also found on Santa Rosa Island.

Physiography and Geology

Unlike any other northern Channel Island, Santa Rosa Island in blanketed predominantly with gently rolling hills and grasslands. High mountains with deeply cut canyons are limited. The northeastern shore consists of well-developed marine terraces where cliffs abut the ocean. The southern sector of the island is stepper and more rugged. The island’s coastline is quite variable, with broad sandy beaches on the northwest, northeast and southwest.

The structure of Santa Rosa Island is that of an uplifted block deformed by folding and faulting. This island has a larger area of Tertiary sedimentary non-volcanic rocks than any other Channel Island. Tertiary sandstones, siltstones, shales and volcanic on the northern half of the island are covered with a thick layer of Quaternary (Pleistocene era) deposits. The oldest Cretaceous rocks are on the south side, along with a complex series of Eocene, Oligocene, and early Miocene volcanics, consisting of basalts, breccias, and conglomerate rocks.

A well-defined fault runs in an east-west direction from north of Skunk Point to just south of Sandy Point. The rocks to the north of the fault are younger than those to its south.

The 1812 earthquake, which destroyed much of the Santa Barbara Mission, had its epicenter near Santa Rosa Island. A rift 1000 feet long, 100 feet wide and 50 feet deep, opened on the island in the vicinity of Loba Canyon. Indians living on the island at the time of this earthquake were sufficiently scared to want to leave Santa Rosa Island for a life on the mainland. Today this fault is still quite evident.

Pleistocene fossil beds are particularly well developed on Santa Rosa Island. The thick Quaternary deposits on the island’s northern sector have all yielded fossil evidence of mammoths, giant mice, whales, sea otters, and an extinct flightless goose.
Santa Rosa Island has had more exploration for oil than any other Channel Island. In 1932, Standard Oil drilled for oil, followed by Signal-Honolulu in 1949-50, and Mobile Oil in the early 1970s. A total of twelve wells were drilled, all of which were dry.