By Dave Bunnell of The Virtual Cave - Photos copyright Dave Bunnell unless noted otherwise.
Sea
Cave Formation
Sea caves are formed by the power of the ocean (or in some cases, lakes) attacking zones of weakness in coastal cliffs. The weak zone is usually a fault, or fractured zone formed during slippage.
Another type of weak zone is formed where dissimilar types of rocks are inter-bedded and one is weaker than the other. Typically this is a dike, or intrusive vein of more easily eroded rock found within a stronger host rock.
The cave may begin as a very narrow crack into which waves can penetrate and exert tremendous force, cracking the rock from within. Sand and rock carried by waves produce additional erosive power on the cave's walls.
Sea
caves rarely have formations like solution caves or lava tubes. Occasionally
some flowstone or small stalagmites are seen, formed much as in solution caves.
Typically these occur in caves formed in sandstone or basalt.
Left
is a long cave formed along a fault, visible along the sloping wall on the right.
Riko Riko Cave, largest sea cave by volume, on the Poor Knight Islands off
the east coast of New Zealand's North Island. The white material on the
walls is calcite deposits. On the right is a sea cave floored with just sand,
having emptied out at low tide. Colorful marine algae adorn the ceiling.
Sea caves are found all over the world, and may be one of the most numerous type of caves.
Areas known for large concentrations of sea caves include the Pacific coast states of the USA (Washington, Oregon, and California, and especially, California's Channel Islands); the Na Pali coast of Kauai; the Greek Isles; and many other places with good solid rock to host the caves.
The
Entrance Zone
Sea caves may be explored in several ways: with kayaks or other small boats; by swimming in; or in some caves, by wading or walking if the cave empties out at low tide. When entering a cave where the surf is active, it's best to wear a helmet and study conditions carefully before entering. Remember that the power of waves and swell will be amplified in the cave interior!
Life
in a Sea Cave
Inside, a sea cave may be dry or wet, depending on the tide, time or year, or the locale.
Sea caves may abound with life, both on their walls and floors. Besides the kind of critters seen in normal tide-pools, such as anemones, starfish, and sponges, sea caves with dark zones may harbor organisms not commonly seen.
In
California, the Giant Anemone is normally green because of an algae that lives
inside of it; but in sea caves with dark zones, like the one on the right, these
anemones may be white because the green algae doesn't get enough sunlight to
grow.
Gooseneck
barnacles (above right) are common on sea cave walls in the inter-tidal
zone. In sea caves with deep water, sharks may be found.
Famous Sea Caves
Famous sea caves include the Blue Grotto of Capri, and Fingal's Cave on the British island of Staffa (formed in columnar basalt). While spacious inside, they are only moderate in length, neither of them exceeding 250 feet from end to end.
World's Longest Sea Cave
The world's longest known sea cave is Painted Cave on California's Santa Cruz Island. It is 1227 feet long and large enough to take a 40-foot boat inside.
Right is a view of the mostly dark inner chamber, looking towards the back of the cave. Sea lions inhabit the ledges in the back of the chamber much of the year. (Below is a portion of a beautifully illustrated map of Painted Cave, courtesy of cartographer Bob Richards, and available for purchase through his site, Cave Graphics.)
Another huge sea cave and second on the list of the world's longest sea caves compiled by the author is Waiahuakua on Kauai's NA Pali coast, which tapes out at 1155 feet long.
Dave
Bunnell has explored and surveyed over 500 sea caves, and
written two books on them. Carved by the power of oceans, sea caves
may be gentle or treacherous to explore. The caver's motto is "Take
nothing but pictures, cave softly, and leave no trace of your visit."
As a caver and photographer for over 30 years, Dave Bunnell has collected
images from caves all over the world. We believe his site, Virtual
Cave to be the most comprehensive on caving. Kayak cavers as well
as the armchair enthusiast will find there an extensive list of cave
sites with beautiful photographs & links to complete information
for visiting the area.
RELATED ARTICLES, BOOKS & RESOURCES
*Index To Kayak Caving - Provides links to all our articles related to Kayak Caving.
*Exploring Caves By Kayak by Tom Holtey Tom discusses Sea Cave safety and prerequisites for enjoying this exciting aspect of sea kayaking.
*The Virtual Cave - David Bunnell's amazing website. Includes a comprehensive list of the 89 longest sea caves.
*Leave No Trace Pamphlets are free from the National Outdoor Leadership School and have important nature tips for you by area.
At Tom's TopKayaker Shop:
Kayaker
Caving-Whitewater-Surf Helmets
A helmet perfectly designed specifically for the kayaker.
One size with included foam liners for a proper fit.
SOFT PATHS, N.O.L.S. (National Outdoor Leadership School) This is the definitive guide to minimum impact camping and outdoors travel. If you love the wilds then this book will help you not to "love the wilds to death." The techniques in this book will teach people how to preserve outdoor destinations for wild life and fellow adventures alike. |
 Cave
Minerals of the World by Carol A. Hill For those who want to learn more about cave formations, check out Cave Minerals of the World, published and sold by the National Speleological Society. This is the most authoritative source on cave formations ever published. This Amazon.com link supports this site. |
Books by Dave Bunnell: Sea Caves of Anacapa Island Sea Caves of Santa Cruz Island |
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