|
A sea cave, also known as a littoral cave, is a type of cave formed primarily by the wave action of the sea. The primary process involved is erosion. Sea caves are found throughout the world, actively forming along present coastlines and as relict sea caves on former coastlines. In places like Thailand's Phang Nga Bay, solutional caves have been flooded by the rising sea and are now subject to littoral erosion. Lechuguilla Cave, New Mexico A cave is a natural underground void large enough for a human to enter. ...
It has been suggested that this article be split into articles entitled wave, accessible from a disambiguation page. ...
Sea as seen from jetty in Frankston, Australia Look up maritime in Wiktionary, the free dictionary. ...
Phang Nga Bay is a 400 km² bay in the Andaman Sea between the island of Phuket and mainland of the Malay peninsula of southern Thailand. ...
Some of the best-known sea caves are European. Fingal’s Cave, on the Scottish island of Staffa, is a spacious cave some 70 m long, formed in columnar basalt. The Blue Grotto of Capri, although smaller, is famous for the apparent luminescent quality of its water, imparted by light passing through openings underwater. The Romans built a stairway in its rear and a now-collapsed tunnel to the surface. The Greek islands are also noted for the variety and beauty of their sea caves. Numerous sea caves have been surveyed in England, Scotland, and in France, particularly on the Normandy coast. The largest sea caves are found along the west coast of the United States and in the Hawaiian islands. Fingals Cave around 1900 View from West to East Staffa (Norse for staff, column, or pillar island), an island of the Inner Hebrides in Argyll and Bute, Scotland. ...
The outside of the Blue Grotto The inside of the Blue Grotto The Blue Grotto (Grotta Azzurra) is a noted sea cave on the coast of the Italian island of Capri. ...
Capri (Italian pronunciation Cápri, usual English pronunciation CaprÃ) is an Italian island off the Sorrentine Peninsula. ...
Grotte des Faux-Monnayeurs, Switzerland Speleology is the scientific study of caves and other karst features, their make-up, structure, physical properties, history, life forms, and the processes by which they form (speleogenesis) and change over time (speleomorphology). ...
Formation
 Sea cave formation along a fault  Sea cave formation along a dike Littoral 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. Two types of sedimentary rock: limey shale overlaid by limestone. ...
The term Metamorphic can be associated with a number of meanings:- Metamorphic rock The term for rocks that have been transformed by extreme heat and pressure. ...
Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ...
In order to form a sea cave, the host rock must first contain a zone of relative weakness. In metamorphic or igneous rock, this is typically either a fault as in the caves of the Channel Islands of California, or a dyke 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 Channel Islands of California, also called the Santa Barbara Islands, are a chain of eight islands located in the Pacific Ocean off the coast of Southern California along the Santa Barbara Channel in the United States of America. ...
A dike in geology refers to a tabular intrusive igneous body. ...
Kaua‘i (usually called Kauai outside the Hawaiian Islands, pronounced kawa-ee) is the oldest and fourth largest of the main Hawaiian Islands, having an area of 1,430. ...
This article or section does not cite its references or sources. ...
The Kalalau Trail along the Na Pali Coast The Na Pali Coast State Park encompasses 6,175 acres (25 km²) of land and stretches sixteen miles (26 kilometers) along the northwest side of Kaua‘i, the oldest Hawaiian Island. ...
NASA satellite image of Santa Cruz Island. ...
Official language(s) English Capital Sacramento Largest city Los Angeles Area Ranked 3rd - Total 158,302 sq mi (410,000 km²) - Width 250 miles (400 km) - Length 770 miles (1,240 km) - % water 4. ...
Andesite is an igneous, volcanic (extrusive) rock, of intermediate composition, with aphanitic to porphyritic texture. ...
Basalt Columnar basalt at Sheepeater Cliff in Yellowstone Basalt (IPA: ) is a common gray to black volcanic rock. ...
Agglomerate - Wikipedia /**/ @import /skins-1. ...
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. Halong Bay is a body of water of approximately 1,500 square kilometres in north Vietnam with a 120 kilometre coastline, in the Gulf of Tonkin near the border with China, and 170 kilometres east of Hanoi. ...
Rainwater may also influence sea-cave formation. Carbonic and organic acids leached from the soil may assist in weakening rock within fissures. As in solutional caves, small speleothems may develop in sea caves. A speleothem (from the Greek for cave deposit) is a formal term for what is also known as a cave formation, or amongst cavers, collectively known as pretties. ...
Sea cave chambers sometimes collapse leaving a “littoral sinkhole”. These may be quite large, such as Oregon’s Devil’s Punchbowl or the Queen’s Bath on the Na Pali coast. Small peninsulas or headlands often have caves that cut completely through them, since they are subject to attack from both sides, and the collapse of a sea cave tunnel can leave a free-standing “sea stack” along the coast. The Californian island of Anacapa is thought to have been split into three islets by such a process. Official language(s) None Capital Salem Largest city Portland Area Ranked 9th - Total 98,466 sq mi (255,026 km²) - Width 260 miles (420 km) - Length 360 miles (580 km) - % water 2. ...
Stack, near Old Harry Rocks Old Harry Rocks A stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast. ...
NASA satellite image of Anacapa Island Anacapa Island is a small volcanic island located about 14 miles (23 km) off the coast of Ventura, California, in Ventura County. ...
Life within sea caves may assist in their enlargement as well. For example, sea urchins drill their way into the rock, and over successive generations may remove considerable bedrock from the floors and lower walls. Slate pencil urchin (cidaroid) Group of black, long-spined Caribbean sea urchins, Diadema antillarum (Philippi) Sea urchin roe. ...
Factors influencing size  Some sea caves empty out at low tide 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. NASA satellite image of Santa Cruz Island. ...
The type of host rock is important as well. All of the largest sea caves are in basalt (citation needed), a relatively 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 relative zone of weakness may not greatly outstrip that of the cliff face. Basalt Columnar basalt at Sheepeater Cliff in Yellowstone Basalt (IPA: ) is a common gray to black volcanic rock. ...
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. Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ...
The Pleistocene epoch (IPA: ) is part of the geologic timescale. ...
The eight Channel Islands of California, off the west coast of the United States. ...
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 celing 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. NASA satellite image of Anacapa Island Anacapa Island is a small volcanic island located about 14 miles (23 km) off the coast of Ventura, California, in Ventura County. ...
References Bunnell, D. 1988. Sea Caves of Santa Cruz Island, Santa Barbara, California: McNally and Loftin Bunnell, D. 1988b.
Bunnell, D. 1993. Sea Caves of Anacapa Island, Santa Barbara, California: McNally and Loftin
Bunnell, D. 2004. Littoral Caves. Chapter in Gunn, J. (Ed.)Encyclopedia of Caves and Karst, Fitzroy Dearborn, New York, NY.
Moore, D.G. 1954. Origin and development of sea caves. National Speleological Society Bulletin, 16: 71–76
External Links - [1] Photos and information on sea caves in the Virtual Cave
|
Feeds |
Contact