Geology of Channel Islands National Park

Channel Islands National Park, or more specifically, the islands of the Channel Islands National Park have changed quite a bit over the years. During the Ice Age, (not the movie), for example, the northern islands were all part of one giant island known as Santarosae (that’s what the Geologists call it). In those time the sea level was very much lower meaning that large areas of what is now sea bed was actually dry land. Thus the northern islands were all linked together, although it is unlikely that they were connected with the mainland. The islands separated later when the continental ice sheets began to melt.

One of the great beauties of the Channel Islands National Park (and hence it’s reason for being) is the uniqueness and fragility of the ocean environment, protecting and preserving an abundance of natural resources. Any non-native species which are introduced to such islands can totally devastate the natural balance of things, the entire ecosystem. This is a topic which is taken very seriously these days, but over the years many non-native plants and animals have been introduced with irreversible consequences. Increasing numbers of hogs, rabbits, feral sheep  and cats have even eliminated some of the native plants, the park now strives to protect and restore native populations as much as possible.

Anacapa Island – is the closest of the Channel Islands National Park to the mainland, lying only 11 miles from the coast at Oxnard and 14 miles from Ventura. The island covers around 1 square mile, is 5 miles long and is composed of three separate inlets which are only accessible to each other by boat.  The shores around Anacapa Island are a haven for sea mammals and other marine creatures, migrating whales can be seen January through March and black oyster-catchers, cormorants, western gulls – even the endangered brown pelicans can be seen around the island all year round.


Santa Cruz Island – is the largest island within the Channel Islands National Park, as well as the most diverse. Covering around 96 square miles (it’s 24 miles long) the island has more than it’s fair share of rugged ridges, slopes, coves and canyons. It can also boast the highest point in all of the Channel Islands at 2,400 feet. The abundant beaches (there’s around 77 miles of coastline on Santa Cruz Island), sea caves and steep cliffs offer the perfect habitat for nesting sea birds plus many more animals and plants. There are over 600 different plant species and 140 different land bird species at Santa Cruz Island, plus a small but rather distinctive bunch of land animals. There are a total of 85 endemic plant species to the Channel Islands and incredibly 9 of them are only found on Santa Cruz Island. No wonder this place is top of the list for any adventurers who fancy a spot of camping, kayaking, hiking, swimming, exploring – just basically getting away from it all really.

Isn’t it great?

Santa Rosa Island – is the second largest island in the park, at around 15 miles long and 10 miles wide. This is an island of high mountains, deep canyons and gentle rolling hills with flat marine terraces, and cliffs to easily rival those at Santa Cruz. Around 85 per cent of the island is covered by grassland although there are also some very interesting and extensive fossil beds and volcanic formations. The sandy beaches of Santa Rosa Island are a favorite breeding ground of the harbor seal, and a unique coastal marsh towards the east of the island offers an extensive freshwater habitat rare for these islands. Kelp beds actually surround the whole of Santa Rosa Island.

During the 1800’s there was lots of cattle ranching activity on Santa Rosa Island, but once that collapsed the cattle were removed and the island as sheep were introduced. Around 1900, however, the cattle were removed and the sheep brought back again (not the same ones obviously, maybe their descendants). The island is home to many more animals, birds and plants, don’t be surprised if you spot an island fox but if you see the rare and elusive spotted skunk you are really honored – they’re only found on the islands of Santa Rosa and Santa Cruz.

San Miguel Island – is the furthest west of the northern islands and regularly takes a battering from the wind and weather sweeping in from the North Pacific. This place is harsh, but boy is it beautiful. It’s pretty small, only 8 miles long and 4 miles wide, it’s mostly flat with two rounded hills rising from the plateau. Seals and seal lions live here in gay abandon, breeding on the isolated shores of San Miguel Island,you might also spot the island fox, the largest land mammal of the Channel Islands.

Santa Barbara Island – is small, only about 640 acres in all, and lies much further south than the rest of the Channel Islands within the National Park. There are, however, 5.5 miles of great hiking trails which are well worth exploring, watch out for California sea lions, elephant seals, barn owls, horned larks, American kestrels . . . you must might be lucky enough to catch a glimpse. Santa Barbara Island is also a haven for the island deer mouse and island night lizard, these threatened species enjoy the relative peace and tranquility of beautiful Santa Barbara Island.