Download The Channel Islands

INTER-ISLAND DISTANCE LEARNING
EXCHANGE PROJECT
THE CHANNEL ISLANDS
Written By
R. B. Trombley, Ph.D.
Southwest Volcano Research Centre
Apache Junction, Arizona USA
The Channel Islands
The Channel Islands, off the coast of California, consist of the following islands (starting from
the northern most island): San Miguel, Santa Rosa, Santa Cruz, Anacapa, Santa Barbara, San
Nicolus, Santa Catalina, and San Clemente.
Map showing the location of the islands of the Channel
Island.
Formation of the Channel Islands
During the last Ice Age the northern Channel Islands were part of one vast island geologists call
Santarosae. Sea level was then much lower, and large areas of today’s seabed were dry. The
northern islands were then linked together, though probably not connected to the mainland.
Later, when the great continental ice sheets melted, the islands were separated.
Scientists estimate that around 15 million years ago the Channel was a hotbed of volcanic
activity - much like Hawaii is today. Over the years, the Channel Islands have been formed
through a combination of volcanic activity (pushing molten magma to the earth’s surface - in this
case at times underwater), erosion from the sea as ocean water levels have risen and lowered as
much as 300 feet during different ice and warming ages (wearing away the islands as a result of
surf and tide conditions), and seismic activity (the lifting and folding associated with earthquakes
and other long term movements of the earth’s crust).
During the Pleistocene era, a dwarf species of mammoth roamed Santarosae, and pine and
Cypress forests stood on several islands. Today, the fossilized remains of dwarf mammoths on
San Miguel and Santa Rosa, and the forests of brittle sand castings known as caliche
(pronounced kah-lee-chee), that are found on San Miguel remind us that the Islands were very
different long ago. Some plants and animals have developed special adaptations over time to
cope with the isolated environment—others remain unchanged. The giant coreopsis is found on
all five-park islands and on the coastal mainland. Its more common name, "tree sunflower",
suggests its size and trunk-like stem. Its bright yellow blossoms are sometimes visible from the
mainland during the winter and spring.
Individual Island Geology
San Miguel
San Miguel Island (9,325 acres). Fifty-five miles off the coast from Ventura, San Miguel Island
is the farthest west of the Channel Islands. Because of its location in the open ocean, it is subject
to high winds and lots of fog. The island is a tableland of lush grasses and wildflowers, with 27
miles of jagged, rocky coastline dotted with sandy white beaches. The westernmost of these
beaches, Point Bennett, is the only place in the world where up to six different species of
pinnipeds (seals and sea lions) can be found.
Santa Rosa
Santa Rosa Island (52,794 acres), the second largest of the Channel Islands, is 40 miles
west of Ventura. It is a diverse island of grass-covered rolling hills, steep canyons,
creeks, rocky inter-tidal areas and sandy beaches. It is a treasure of archeological sites,
some dating back nearly 11,000 years. The former owners of the island continue to lease
Santa Rosa until the year 2011 for game hunts.
Santa Cruz
Santa Cruz is the largest island off the coast of California. Located between Anacapa and
Santa Rosa Islands, it lies from 19-25 miles off the adjacent mainland coast between
Ventura and Santa Barbara.
The scenic beauty of Santa Cruz is reflected in its many landforms-two rugged mountain
ranges, the highest peaks on the Channel Islands, deep canyons, a central valley, yearround springs and streams, plus 77 miles of craggy coastline cliffs, giant sea caves,
pristine tide-pools and expansive beaches. Lying directly on the boundary between cold
northern and warm southern waters, this island hosts unique plant, animal, and marine
communities representing nearly 1000 miles of coastline.
According to legend, Santa Cruz Island was named for a priest's staff accidentally left on
the island during the Portola expedition of 1769. A Chumash Indian found the crosstipped stave and returned it to the priest. The Spaniards were so impressed that they
called this island of friendly people "La Isla de Santa Cruz", the Island of the Sacred
Cross.
Today, Santa Cruz Island is divided between The Nature Conservancy and the National
Park Service. The Nature Conservancy owns and manages the western 76% of the island;
the eastern 24% is owned and managed by the National Park Service.
Anacapa
Anacapa Island is located 14 miles off the coast from Ventura. It is the only Channel
Island to retain its American Indian name, derived from the Chumash word, "Eneepah",
meaning island of deception or mirage. Ocean waves have eroded the perimeter of the
island, creating steep sea cliffs towering hundreds of feet in height and exposing the
volcanic origins of air pockets, lava tubes, and sea caves. At the east end of Anacapa a
natural bridge has formed in the ocean. Forty-foot high Arch Rock is a trademark of
Anacapa and Channel Islands National Park.
Santa Barbara
Santa Barbara Island (639 acres), 38 miles west of San Pedro, is the smallest of the
California Channel Islands. Formed by underwater volcanic activity, Santa Barbara is
roughly triangular in outline and emerges from the ocean as a giant twin-peaked mesa
with steep cliffs. Even though small in size, Santa Barbara Island boasts diversity in its
habitats, with a few narrow rocky beaches, six canyons, and badlands area. It is much like
Anacapa Island in its being a haven for sea birds. The steep cliffs and isolation from
mainland predators provide safe breeding sites for thousands of sea birds.
San Nicolus
San Nicolas is the outermost island in the California Channel archipelago, and is a total
of 22 square miles. It is most well known as the home of the Lone Woman of San
Nicolas, the last Native American to reside on the island, and who was inadvertently left
stranded there alone for eighteen years. Her life is the basis for Scott Odell’s book and
movie, Island of the Blue Dolphin.
San Nicolas appears to be the one Channel Island that is not directly of volcanic origin as
it does not have igneous rock. Its foundation is a sandstone bedrock that is layered by
marine terraces. The highest point on the island is Jackson Hill at 907 feet, and the
majority of the mountainless island is shifting sand dunes, with an estimated 75% of the
island in motion as the dunes respond to wind and weather.
Santa Catalina
On of the most unique geologic features of Catalina is the deposits of steatite, or
soapstone, that was such an important trade item in prehistory. It is the only in the
Channel where steatite is found, and gave the islanders a very valuable trade item as it
was the primary materials for the native bowls, pipes, effigies and other carved
implements.
Like most of the other islands, Catalina has areas of volcanic igneous rock formation, and
well as sedimentary formation of ocean floor lifted by seismic forces, and metamorphic
rock that has undergone geologic pressures to transform its sandstone base into more
durable stone deposits. The metamorphic rock is the oldest, dating back to over 150
million years old. Next oldest is the igneous rock that was brought to the surface during
volcanic activities. And the sandstone is the youngest geologic formation.
The highest mountains on Catalina are Mt. Orizaba at 2069 feet, and Mt. Black Jack - site
of a silver mine in the 1920s - at 2006 feet. The overall land mass of Catalina is 75 square
miles, the third largest of the California Channel Islands.
San Clemente
San Clemente is the fourth largest of the Channel Islands at 56 square miles in size. Its
highest peak is Mount Thirst at 1,956 feet, and the island is primarily marine terraces cut
with canyons running down to the shoreline. Like many of the other Channel Islands, San
Clemente is composed of volcanic rock formed in the Miocene era, and has sedimentary
rock moved up by seismic forces from the ocean floor, which is imbedded with fossils of
prehistoric animal and plant life.
Current Eruptions
There are currently no eruptions and the probability of future eruptions on any of the islands of
the Channel Islands, is extremely remote. At the moment there is no volcanic seismicity detected
on any of the islands all of which, except San Nicolus, are of known volcanic origin. Normal
tectonic earthquake activity is sometimes detected. Further, there is no deformation or any other
indication that any of the islands in the Channel Island group will ever resurrect their volcanic
origins, which had their roots approximately 15 million years ago when the area, at that time,
was a hotbed of volcanic activity.
Current Issues
Most of the Channel Island issues of today revolve around both marine and land environmental
issues. For many plants and animals of the Channel Islands, life is not possible without both the
land and the sea. Pelicans fish for anchovies from the ocean but nest on the dry bluffs of West
Anacapa. Low growing sand verbena needs the sandy soil of San Miguel Island to grow, but it
also needs salt from the ocean air. Giant kelp fastens its root like hold on the shallow rocks of
islands near-shore reefs, yet this seaweed also needs nutrients from the deep ocean.
Isolated from the mainland and the mingling of warm and cold water currents in the Santa
Barbara Channel help form the Channel Islands special character. The plants and animals are
similar to those on the mainland but thousands of years of isolation in unique island
environments have resulted in size, shape or colour variations. The Channel Islands are home to
65 plant species that do not exist anywhere else in the world. All of the larger islands are home
for the island fox, a close relative to the mainland's gray fox. Because it evolved in isolation, the
islands fox is no larger than a house cat. These foxes prey upon deer mice that are slightly larger
than their mainland relatives. Both creatures are well adapted to the harsh island environment.
Remoteness from the mainland has buffered the island from the rapid changes wrought by
modern humans. While most mainland tide-pools are practically devoid of life because of heavy
human use, sea stars, sea urchins, sea anemones and limpets thrive in the islands inter-tidal areas.
White plumed sea anemones still cover underwater rocks at San Miguel and vivid purple
hydrocorals filter water for food near Santa Cruz Island. Though used by fishermen and sport
divers, and subject to mainland water pollutants, the kelp forests of the Channel Islands harbor
great numbers of plants and animals. Today the islands support some of the last remnants of
coastal southern California plant communities rapidly disappearing from the mainland.
The introduction on non-native plants and animals to an island ecosystem can devastate native
species. One exotic is a tenacious South African species of iceplant that found its way to Santa
Barbara Island before 1900. Highly salt tolerant, it thrives in arid soil by capturing moisture from
sea breezes. It subsequently leaches salt into the soil, producing concentrations of salt that few
native plants can tolerate. Today, the iceplant spreads its thick mats over much of the island.
Introduced livestock, food animals, and pets have similar impacts on island environments.
Escalating feral sheep, hog, cat, and rabbit populations led to damage to, and sometimes
elimination of, native plants and animals. The National Park Service seeks to restore native
populations where possible.
The Marine Region of the Channel Islands is responsible for protecting and managing
California’s marine resources under the authority of laws and regulations created by the State
Legislature, the Fish and Game Commission, and the Pacific Fishery Management Council. The
Channel Islands Marine Region was established in November 1997, as an outgrowth of planning
actions taken by the Department of Fish and Game in the mid-1990s to increase its effectiveness.
A task force, which convened in 1997, developed recommendations for the establishment of a
new Marine Region.
The Channel Island Marine Region is unique in the Department because of its dual responsibility
for both policy and operational issues within the State’s marine jurisdiction. It was created to
improve marine resources management by incorporating critical law enforcement functions,
fisheries and habitat programs, environmental review, and water quality monitoring into a single
organizational unit. It is designed to allow us to be more effective, inclusive, comprehensive and
collaborative in marine management activities.