Santa Cruz Island in the context of Ventura, California

Anacapa Island (Chumash: Anyapax, meaning "mirage, illusion") is a small volcanic island located about 11 miles (9.6 nmi; 18 km) off Port Hueneme in Ventura County, California. The island is composed of a series of narrow islets 6 mi (10 km) long, oriented generally east–west and 5 mi (8 km) east of Santa Cruz Island. The three main islets, East, Middle, and West Anacapa, have precipitous cliffs, dropping off steeply into the sea.

Anacapa is the smallest of the northern islands of the Channel Islands archipelago, and is within the Channel Islands National Park. It is 9 miles (7.8 nmi; 14 km) across the Santa Barbara Channel from the nearest point on the mainland. It lies southwest of the city of Ventura, California. The northern waters of Anacapa Island are protected by the Anacapa State Marine Reserve, which is one of the MPAs existing in the Channel Island National Park.

The Santa Barbara Channel is a portion of the Southern California Bight and separates the mainland of California from the northern Channel Islands. It is generally south of the city of Santa Barbara, and west of the Oxnard Plain in Ventura County.

It trends east–west, is approximately 130 kilometres (70 nmi) long and averages about 45 kilometres (24 nmi) across, becoming narrowest at its easternmost extremity where Anacapa Island is about 30 kilometres (16 nmi) from the mainland. During the last ice age, the four northern Channel Islands, including Santa Rosa Island, were conjoined into Santa Rosae, a single island that was only five miles (8 km) off the coast.

The Dos Cuadras Offshore Oil Field is a large oil and gas field underneath the Santa Barbara Channel about eight miles southeast of Santa Barbara, California. Discovered in 1968, and with a cumulative production of over 260 million barrels of oil, it is the 24th-largest oil field within California and the adjacent waters. As it is in the Pacific Ocean outside of the 3-mile tidelands limit, it is a federally leased field, regulated by the U.S. Department of the Interior rather than the California Department of Conservation. It is entirely produced from four drilling and production platforms in the channel, which as of 2009 were operated by Dos Cuadras Offshore Resources (DCOR), LLC, a private firm based in Ventura. A blowout near one of these platforms – Unocal's Platform A – was responsible for the 1969 Santa Barbara oil spill that was formative for the modern environmental movement, and spurred the passage of the National Environmental Policy Act.

A sea cave, is also known as a littoral cave, a type of cave formed primarily by the wave action of the sea. The primary process involved is erosion. Sea caves are found throughout the world, actively forming along present coastlines and as relict sea caves on former coastlines. Some of the largest wave-cut caves in the world are found on the coast of Norway, but are now 100 feet or more above present sea level. These would still be classified as littoral caves. By contrast, in places like Thailand's Phang Nga Bay, solutionally formed caves in limestone have been flooded by the rising sea and are now subject to littoral erosion, representing a new phase of their enlargement.

Some of the best-known sea caves are European. Fingal's Cave, on the island of Staffa in Scotland, is a spacious cave some 70 m long, formed in columnar basalt. The Blue Grotto of Capri, although smaller, is famous for the apparent luminescent quality of its water, imparted by light passing through underwater openings. The Romans built a stairway in its rear and a now-collapsed tunnel to the surface. The Greek islands are also noted for the variety and beauty of their sea caves. Numerous sea caves have been surveyed in England, Scotland, and in France, particularly on the Normandy coast. Until 2013, the largest known sea caves were found along the west coast of the United States, the Hawaiian islands, and the Shetland Islands. In 2013 the discovery and survey of the world's largest sea cave was announced. Matainaka Cave – located on the Otago coast of New Zealand's South Island – has proven to be the world's most extensive at 1.5 km in length. Also in 2013, Crossley reported a newly surveyed complex reaching just over a kilometer in survey at Bethells Beach on New Zealand's North Island.

Chumashan is an extinct and revitalizing family of languages that were spoken on the southern California coast by Native American Chumash people, from the Coastal plains and valleys of San Luis Obispo to Malibu, neighboring inland and Transverse Ranges valleys and canyons east to bordering the San Joaquin Valley, to three adjacent Channel Islands: San Miguel, Santa Rosa, and Santa Cruz.

The Chumashan languages may be, along with Yukian and perhaps languages of southern Baja California such as Waikuri, one of the oldest language families established in California, before the arrival of speakers of Penutian, Uto-Aztecan, and perhaps even Hokan languages. Chumashan, Yukian, and southern Baja languages are spoken in areas with long-established populations of a distinct physical type. The population in the core Chumashan area has been stable for the past 10,000 years. However, the attested range of Chumashan is recent (within a couple thousand years). There is internal evidence that Obispeño replaced a Hokan language and that Island Chumash mixed with a language very different from Chumashan; the islands were not in contact with the mainland until the introduction of plank canoes in the first millennium AD.

Channel Islands National Park is a national park of the United States, which consists of five of the eight Channel Islands off the coast of California. Although the islands are close to the shore of the densely populated state, they have been relatively undeveloped. The park covers 249,561 acres (100,994 ha), of which 79,019 acres (31,978 ha) are federal land.

Santa Cruz Island, the largest of the eight, is divided between The Nature Conservancy and the National Park Service. The Nature Conservancy owns and manages the western 76 percent of the island, while the eastern 24 percent is owned and managed by the National Park Service.

Santa Rosae (also spelled Santarosae) was, before the end of the last ice age, an ancient landmass off the coast of present-day southern California, near Santa Barbara County and Ventura County, of which the northern Channel Islands of California are remnants. At its largest, Santa Rosae was roughly 3-4 times bigger than the northern Channel Islands of today, nearly 125 kilometers (78 mi) from east to west. Between about 20,000 and 5,000 years ago, Santa Rosae lost about 70% of its land mass to post-glacial rising sea level, leaving behind a vast submerged landscape currently being explored by scientists. San Miguel, Santa Rosa, Santa Cruz, and Anacapa Island comprise the unsubmerged portions of Santa Rosae today. This island was about 5 miles (8.0 km) offshore. It broke up between about 11,000 and 9,000 years ago, and the present northern Channel Islands took their shape after the continental ice sheets melted and sea levels rose by about 100 meters.

There is evidence to suggest that a now-submerged island, Calafia, lay between Santa Rosae and the mainland.

The Chumash are a Native American people of the central and southern coastal regions of California, in portions of what is now Kern, San Luis Obispo, Santa Barbara, Ventura, and Los Angeles counties, extending from Morro Bay in the north to Malibu in the south to Mount Pinos in the east. Their territory includes three of the Channel Islands: Santa Cruz, Santa Rosa, and San Miguel; the smaller island of Anacapa was likely inhabited seasonally due to the lack of a consistent water source.

Modern place names with Chumash origins include Malibu, Nipomo, Lompoc, Ojai, Pismo Beach, Point Mugu, Port Hueneme, Piru, Lake Castaic, Saticoy, Simi Valley, and Somis. Archaeological research shows that the Chumash people have deep roots in the Santa Barbara Channel area and have lived along the southern California coast for millennia.