A sea cave is formed by the forces of the sea, waves seething at
the rock face of a coast line, produce sometimes huge caverns,
which are typically not very long. They are as long as the water
reaches. The existence of this type of caves is not dependent on
the kind of rock. Of course, it helps if the rock is weaker, less
resistant against erosion.
Typically sea caves are formed along a weakness in the rock,
like faults, different sediments or weaker layers. Faults in the
rock sometimes produce chains of caves, everywhere the fault
reaches the sea shore.
Already existing caves are opend by the coastal erosion and the
water starts to widen the cave. Typically those caves are karst
caves. Many karst areas at the coast have caves opening to the sea,
where the entrance is widenend by the waves. They are often called
sea caves, which is only partly true.
Sometimes faults, existing caves or weaknesses in the rock
produce a small hole to the surface. The water swashing into the
sea cave builts up a high pressure inside the cave, which emerges
in form of water and air out of the small hole. This is called a
blow hole. They are found all over the world along the coasts.
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 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.
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 celing heights. In some
areas, sea caves may have dry upper levels, lifted above the active
littoral zone by regional uplift.
To claim
this EarthCache please answer the following
questions:
1. What is the estimated height of the cliffs?
2.What type of rock is the cliff made of?
3.What are the two factors (possible 4) that has led to the
developement of the cave?
Please take
a picture of you or gps with cave in the background to prove you
where there.