Times of the Islands Summer 2016

green pages newsletter of the department of environment & maritime affairs
The origins of the Turks & Caicos Islands
The Turks & Caicos Islands exist today because the rocks as ice. The drop in sea level has been as much as 125 m
that form the Islands have been made by living organisms, (410 ft) during a glaciation; during an interglacial slightly
both plant and animal, that precipitate calcium carbonate
(CaCO 3 ), the compound that becomes limestone. (20 ft) above today’s level as more ice had melted.
warmer than today, sea level has been as much as 6 m
The chemistry that allows the precipitation of calcium When a glaciation is occurring, and sea level is down
carbonate also allows it to be dissolved later by moving by 100 meters or more, all the shallow banks of the TCI
water. As a result, the bedrock surface becomes jagged are exposed as dry land, with steep cliffs down to the sea.
and irregular, forming pits that carry water downward to All the current islands on the Caicos Bank: West Caicos,
create caves within the freshwater lenses that underlie Providenciales, North Caicos, Middle Caicos, East Caicos,
the Islands. Each island has its own separate lens. South Caicos, the Ambergris Cays, and all the smaller
The deposition of the limestone that is the TCI’s islands and cays, become one large island. Grand Turk,
foundation and the subsequent dissolution of those rocks Salt Cay, Sand Cay and associated islands and cays are on
has been controlled over the last several million years a separate bank and also become a single large island.
by a series of natural climatic events known (in layman’s Glaciations last about 100,000 years, the interglacials
terms), as the Ice Ages (called
glaciations by geologists). The
time between glaciations, as
currently exists in the world
today, are called interglacials.
During a glaciation, snowfall
in the high latitudes of
Europe and North America
fails to melt completely each
summer, and that snow accumulates
into thick piles of
ice, which expand and move
southward as ice sheets. The
natural trigger for this process
is a subtle change in the
This graph shows the variance in sea level over the last 1/2 million years.
earth’s orbit about the sun that
leads to slightly cooler temperatures that promote snow last only about 10,000 years, but during that short time
survival, but also changing weather patterns that increase window (in the geologic sense), the geology of the TCI
the amount of snow at high latitudes. These orbital becomes established.
changes, called the Milankovitch cycle, are the result of When sea level rises as ice sheets melt back, the tops
slight cyclical changes in how circular the earth’s orbit of the banks become flooded with sea water. The lagoons
is, how much axial tilt exists, and how the precession of form, and the corals, conchs, starfish, algae and other
the earth’s axis changes the equinoxes. The end result organisms begin to flourish and create calcium carbonate,
primarily as reef structures and skeletons. Over time
of ice accumulation as glaciers is a fall in sea level as
the evaporated ocean water is stored on the continents these skeletal features degrade as the organisms die, and
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