Features

Mile-long island went under during the last ice age 

SANTA BARBARA – A scientist has discovered a tiny island submerged off the California coast, more than 16,000 years after it slipped from view during the waning years of the last ice age. 

The low-slung island, little more than a mile in length, lies under 400 feet of water about a dozen miles from shore. 

At most, it poked just 30 feet above the waves during the late Pleistocene, when the continental-sized ice sheets that capped much of the Earth began to melt, raising global sea levels. 

At that time, the four Channel Islands off Santa Barbara – San Miguel, Santa Rosa, Santa Cruz and Anacapa – formed a single, larger island, called Santarosae. 

University of California, Santa Barbara scientist Ed Keller discovered Santarosae’s smaller neighbor while poring over recently created topographic maps of the Santa Barbara Channel, a seismically active region crisscrossed with faults. 

More than a mere curiosity, the discovery is a reminder of how advances in science – in this case, sonar technology – can restore to view land masses thought lost millennia ago. 

“It’s magnificent. We’re just seeing some fantastic, very interesting things we thought we couldn’t see or couldn’t conceive of,” said H. Gary Greene, a research scientist at the Monterey Bay Aquarium Research Institute, which mapped the region in 1998 with a shipboard sonar. 

In examining a 31-mile-long ridge in the middle of the channel formed by the squeeze of the two nearly parallel faults that bookend it, Keller spotted an unusual uprising. 

Unlike the comparatively smooth ocean bottom around it, the protrusion appeared rough and was marked by features that suggested it had been eroded by the pounding of waves, rain and the wind – something that could have occurred only if it had stuck up above sea level. 

“It had enough of the features that we suspect it was an island,” said Keller, a professor of geological sciences and environmental studies at the oceanside university. He first presented his findings, made in 1999, last fall at the Geological Society of America’s meeting in Boston. 

He dubbed his discovery “Calafia,” after a mythical queen who ruled over the race of Amazons who inhabited the island of California in a popular 16th century Spanish romance novel. 

If Calafia did stick up above sea level, it was one of about 26 islands and islets thought to exist off the California coast at the peak of the last ice age. Today, there are about 16 separate land masses. 

The new maps reveal the ocean bottom in far more detail than traditional bathymetric data had, and show Calafia at near-photographic resolution. The view is unique, because the island likely vanished thousands of years before the first humans arrived in Southern California. 

At that time, buffalo, saber-tooth cats, camels and mammoths still roamed the region. Skeletal remains of the latter, including dwarf examples, have been found on the Channel Islands. 

The tusked beasts likely swam out to the islands – a distance then of just two miles or so – to feast on vegetation there. 

Paul Collins, curator of vertebrate zoology at the Santa Barbara Museum of Natural History, said while mammoths may well have stopped off on Calafia while en route to Santarosae, the halfway point was likely too small to support a permanent population. 

The island has supported other creatures since then, namely schools of fish. Fishermen have long called the rich fishing grounds around Calafia, or at least the ridge upon which it sits, ”12-mile reef” in reference to its distance from shore. 

The 1998 mapping images also revealed enormous submarine landslides, as well as series of large pits and mounds that reflect the large amounts of oil and natural gas found beneath the channel, dotted today with offshore drilling rigs. 

The mounds are likely spots where gas has welled up under the ocean bottom but remains capped by the pressure of the sediments and water atop it. Images of the mounds snapped by submersible robots show methane bubbling from them. 

In the past, Keller said, the mounds must have occasionally burst, belching large amounts of gas.