Blue holes in the Bahamas are usually classified
as one of several types:
These are the large round blue holes usually seen
from the air and are the type of formation where
the Blue Holes get their name.
Fault line or fracture
These very deep caves are usually associated
with localized faulting. The systems generally
run parallel to a deep-water, offshore canyons
such as the Tongue of the Ocean east of
Andros Island, or the Exuma Sound, east of
the Exuma Cays.
Lens based blue holes
These caves are usually the longest of the blue
holes and are often highly decorated with
SPELEOTHEMS. They are the result of a
well-defined fresh water lens and the processes
discussed above, actively dissolving a vast
system of passages into the limestone.
These are also known as flooded flank margin
Inland blue holes
These can be of any geological type as
described above, with the entrance being
accessed from land.
Marine or ocean blue holes
These can also be of any geological type,
with entrances being access from below
sea level. Generally, tides and currents
heavily influence this type of cave.
It should be noted that due to the unique
geology of the Bahamas, each of these
different types of caves could be
associated with or connected to each other.
For example, Angelfish Blue Hole in the
Exuma Cays is predominantly a lens-based
cave that connects through several passages
to a major local fault line cave system.
After their initial creation, fault line caves
continue to enlarge by the same chemical
processes as lens-based caves.
Because of its subsurface entrance this
cave is also considered a marine or ocean
Another example is Bottomly's Blue Hole
and Mystery Cave on Stocking Island, Exuma.
Bottomly's is an inland (Anchialine) blue hole,
that is connected by a labyrinth of passages
to Mystery cave, which is a very tidally effected
marine blue hole.
For more information on Anchialine caves,
check out Dr. Tom Iliffe's website:
This unique combination of cave types is not
found anywhere else in the world, making
underwater cave exploration and research in
the Bahamas both exciting and challenging.