This Santa Cruz Island Sea Caves map is made with
National Park, NOAA, and USGS data. The source is from data
compiled from the only official survey of the sea caves in
1983.
Littoral caves(sea caves) may be found in a wide variety of
host rocks, ranging from sedimentary to metamorphic to
igneous, but caves in the latter tend to be larger due to
the greater strength of the host rock.
In order to form a sea cave, the host rock must first
contain a weak zone. In metamorphic or igneous rock, this
is typically either a fault as in the caves of the Channel
Islands of California, or a dike as in the large sea caves
of Kauai, Hawaii’s Na Pali Coast. In sedimentary rocks,
this may be a bedding-plane parting or a contact between
layers of different hardness. The latter may also occur in
igneous rocks, such as in the caves on Santa Cruz Island,
California, where waves have attacked the contact between
the andesitic basalt and the agglomerate.
The driving force in littoral cave development is wave
action. Erosion is ongoing anywhere that waves batter rocky
coasts, but where sea cliffs contain zones of weakness,
rock is removed at a greater rate along these zones. As the
sea reaches into the fissures thus formed, they begin to
widen and deepen due to the tremendous force exerted within
a confined space, not only by direct action of the surf and
any rock particles that it bears, but also by compression
of air within. Blowholes (partially submerged caves that
eject large sprays of sea water as waves retreat and allow
rapid re-expansion of air compressed within), attest to
this process. Adding to the hydraulic power of the waves is
the abrasive force of suspended sand and rock. Most
sea-cave walls are irregular and chunky, reflecting an
erosional process where the rock is fractured piece by
piece. However, some caves have portions where the walls
are rounded and smoothed, typically floored with cobbles,
and result from the swirling motion of these cobbles in the
surf zone.
True littoral caves should not be confused with inland
caves that have been intersected and revealed when a sea
cliff line is eroded back, or with dissolutional voids
formed in the littoral zone on tropical islands (see
Speleogenesis: Coastal and Oceanic Settings). In some
regions, such as Halong Bay, Vietnam, caves in carbonate
rocks are found in littoral zones but were formed by
dissolution.
Most sea caves are small in relation to other cave types. A
current compilation of sea-cave surveys Long sea caves of
the world shows three over 300 meters, 15 over 200 meters,
and 85 over 100 meters in length. In Norway, several
apparently relict sea caves exceed 300 meters in length.
There is no doubt that many other large sea caves exist but
have not been investigated due to their remote locations
and/or hostile sea conditions.
Several factors contribute to the development of relatively
large sea caves. The nature of the zone of weakness itself
is surely a factor, although difficult to quantify. A more
readily observed factor is the situation of the cave’s
entrance relative to prevailing sea conditions. At Santa
Cruz Island, the largest caves face into the prevailing
northwest swell conditions—a factor which also makes them
more difficult to survey. Caves in well-protected bays
sheltered from prevailing seas and winds tend to be
smaller, as are caves in areas where the seas tend to be
calmer.
The type of host rock is important as well. All of the
largest sea caves are in basalt,[citation needed] a strong
host rock compared to sedimentary rock. Basaltic caves can
penetrate far into cliffs where most of the surface erodes
relatively slowly. In weaker rock, erosion along a weaker
zone may not greatly outstrip that of the cliff face.
Time is another factor. The active littoral zone changes
throughout geological time by an interplay between
sea-level change and regional uplift. Recurrent ice ages
during the Pleistocene have changed sea levels within a
vertical range of some 200 meters. Significant sea caves
have formed in the California Channel Islands that are now
totally submerged by the rise in sea levels over the last
12 000 years. In regions of steady uplift, continual
littoral erosion may produce sea caves of great height —
Painted Cave is almost 40 m high at its entrance.
Finally, caves that are larger tend to be more complex. By
far the majority of sea caves consist of a single passage
or chamber. Those formed on faults tend to have canyon-like
or angled passages that are very straight. In Seal Canyon
Cave on Santa Cruz Island, entrance light is still visible
from the back of the cave 189 m from the entrance. By
contrast, caves formed along horizontal bedding planes tend
to be wider with lower ceiling heights. In some areas, sea
caves may have dry upper levels, lifted above the active
littoral zone by regional uplift.
Sea caves can prove surprisingly complex where numerous
zones of weakness—often faults—converge. In Catacombs Cave
on Anacapa Island (California), at least six faults
intersect. In several caves of the Californian Channel
Islands, long fissure passages open up into large chambers
beyond. This is invariably associated with intersection of
a second fault oriented almost perpendicularly to that
along the entrance passage.
Source Wikipedia
For more information on kayaking around the sea caves,
contact the National Park Service or one of the many kayak
tour companies that are licensed with the National Park.
Also, visit our Anacapa Sea Caves Map at -
http://www.cccarto.com/anacapa/index.html
Make sure you visit the National Park site for visitor
information and rules on visiting Channel Islands National
Park. http://www.nps.gov/archive/chis/kayaking.htm
map copyright 2007 CCCarto.com
