Some 20,000 years ago, during the last Ice Age, when the sea level was 300-400 feet lower than today, the four islands off our coast, Anacapa, Santa Cruz, Santa Rosa, and San Miguel, were part of a larger, single island called Santarosae.
Santarosae featured a broad coastal plain, as well as rich offshore kelp forests. During the last ice age the climate was wetter and cooler, more akin to Northern California today; and conifers such as Douglas fir, Gowan cypress and Bishop pine grew on the island.
This super island was four times the size of the islands today, covering roughly 829 square miles. It was about 79 miles long and at its closest point was just 4-5 miles from the mainland.
An imagined traverse of the island might have started at the eastern end of Santarosae, and either followed the coastal plain or made its way over the relatively narrow ridge of what is now Anacapa Island, before reaching what is now Santa Cruz Island.
Santarosae’s highest peak would’ve likely been Mount Diablo, now part of Santa Cruz Island. From there, a traverse westward would have continued across the lowlands separating Santa Cruz and Santa Rosa islands, and then across Santa Rosa Island to reach the comparatively flat San MiguelIsland.
Around 11,000 years ago the islands began to “break apart” as the sea level rose. Anacapa was the first to go, becoming a separate island roughly 10,300 to 10,900 years ago. Around 9,400 to 9,700 years ago, Santa Cruz Island separated from the still connected Santa Rosa and San MiguelIslands, which became separate roughly 300 years later.
The oldest human remains found on the islands at Arlington Springs on Santa Rosa Island date back 13,000 years ago. The early Chumash would’ve potentially been able to make a traverse of Santarosae, and visited and lived on the island as it slowly separated into the four islands we know today.
San Miguel Island is the westernmost of the Channel Islands, and in some ways the most remote. San Miguel, along with Anacapa, Santa Cruz,Santa Rosa, and Santa Barbara Islands, are now part of Channel Islands National Park.
The easiest way to reach the island today is through Islands Packers out of Ventura, www.islandpackers.com, which offers boat rides to all five of the islands within the national park. The boat ride is roughly 3-4 hours long.
Arriving at Cuyler Harbor just as the fog starts to clear, it’s hard to place exactly where I am. It’s a strange juxtaposition, imagining a traverse of Santarosae while traveling by car and boat in order to reach a remnant of this now submerged super island. Here, with its crystal clear waters and nearly white-looking beach, the pristine beauty of the island combined with the timelessness of nature, makes it easy to forget the modern world, and yet at the same time so much has happened since the last ice age.
With no pier at San Miguel Island, we are ferried ashore in rubber skiffs in groups of six. On the beach we are greeted by Susie, one of the volunteer docents, who provides an orientation for visitors to the island.
Gathering my gear, plus the 3½ gallons of water I’m carrying for the duration of my stay, I make my way to the campground, essentially backpacking there. The half-mile trail from the beach climbs up a large dune and then makes its way up the eastern side of Nidever Canyon, passing through a large stand of giant coreopsis before arriving at the campground. From the campground, the trail continues a short way to the ranger station.
The campground features nine sites, each with a picnic table; a food storage box to keep items safe from foxes, ravens, and mice; and a low wooden wind break, which provides some shelter from the steady wind that blows across the island. No campfires are allowed, only cook stoves. There is an outhouse, but no potable water anywhere on the island and so visitors must bring what they’ll need. There is little shade on the island, which is only partially offset by the frequent fog.
Visitors are allowed to hike the trail from beach to the ranger station, as well as the roughly two-mile long beach at Cuyler Harbor unescorted, but the rest of the hikes require a docent or ranger present.
There are three docent-led hikes on San Miguel Island. Cardwell Point to the southeast and Harris Point to the north are both about six miles each round-trip. And the big hike west to Point Bennett, which is about 14 miles round-trip. All hikes start from the ranger station.
The hike to Point Bennett follows an old Navy road that has become overgrown, appearing now as mostly a single track trail. The trail passes through grassland dotted with lupine, coyote bush, dudleya, and loco weed.
At about the one-mile mark, the trail summits San Miguel Hill, the highest point on the island, rising just 831 feet above sea level. The site once served as a World War II lookout station and now features instruments for gathering weather data. From here, the trail descends to what’s referred to as Sand Blast Pass, before arriving at the turnoff to the Caliche Forest.
A short side trail leads to the viewing area that looks out across a sandy field dotted with 2 to 3-foot-tall casts of conifer trees that grew on the island during the last ice age. The casts are related to the white sandy beach and dunes at Cuyler Harbor.
While most of the beaches in California are composed of silicates such as quartz and feldspar and have that distinctive tan or light brown color, the beaches on the north shore of San Miguel Island are made from mostly carbonate material. Carbonate sands are formed from the broken-up skeletal remains of marine invertebrates deposited offshore on the insular shelves of the islands. Carbonate, white sandy beaches are more common in tropical and subtropical waters.
In fact, the Channel Islands represent the northernmost place in North America where carbonate dunes occur. One contributing factor is there are no large rivers on the islands carrying enough silicate material to dilute the carbonate material being deposited, allowing it to build up over the millennia. During the last ice age, when the sea level was lower, the exposed material was carried inland by the wind, where it formed dunes.
As trees on the island decomposed their trunks and root systems became filled with sand, creating molds of the trees. When mixed with rain, the carbonate material dissolves, percolating down through the soil, cementing the particles and creating casts over the trunk and root molds that we see today.
Continuing past the Caliche Forest, the trail makes its way toward Green Hill, the second highest point on the island at 817 feet of elevation. The trail crests the side of the hill, before continuing out towards Point Bennett.
At about the five-mile mark, the trail arrives at an airstrip, located in a dry lake bed, which is used to bring in supplies and personnel for the marine mammal research station. From here, the trail follows the road from the airstrip to the station.
At the research station we pause, while Susie gathers binoculars and a field scope to more easily view the pinnipeds at Point Bennett, which we can already hear in the distance.
From the research station, we continue another mile as the trail threads its way down to an overlook that offers views out across the beach at Point Bennett. The point is essentially a large rock outcropping connected by a sandy spit. The adjoining and nearby beaches regularly see large numbers of elephant seals, northern fur seals, California sea lions, and harbor seals sunning themselves, as well as cavorting, mating, and in some cases sparring amongst themselves.
Steller sea lions and Guadalupe fur seals also occasionally visit the island, making Point Bennett one of the largest and most diverse pinniped rookeries in the world.
From here, Santarosae at its largest extended northwest roughly another 12 miles. During the last ice age, all eight of the Channel Islands were larger and covered more area, but only the four northern islands off our coast were connected together.
In addition to the islands and islets off Southern California that we know today, the lower sea level during the last ice age created additional islands that remain now as shallow seamounts or banks. These submerged islands include Osborn, Tanner, and Cortes Banks that are part of the southernChannel Islands.
In 1999, while looking at newly created topographic maps of the sea floor of the channel, local geologist and UCSB professor Ed Keller observed the features of what may have been an island located halfway between what is now Santa Cruz Island and Santa Barbara. Named Calafia, the island was roughly 1.25 miles long, comparable in size to eastern Anacapa Island today, but at most rose only 30 feet above the sea. The island became submerged roughly 16,000 years ago, but may have served as a stopover for animals such as the Columbian mammoth on their way out to Santarosae.
James Wapotich is a volunteer wilderness ranger with the Los Padres National Forest and is working on a book about the Santa Barbarabackcountry. If you have a favorite hike, a trail you’re curious about or questions about hiking, send them to firstname.lastname@example.org.