Geology of Virgin Islands National Park

The Virgin Islands National Park is pretty much how you would expect a Caribbean island to be . . . vibrant coral reefs, clear blue tropical seas, endless beaches of the whitest sand and the remnants of days gone by – sugar plantations from centuries ago. This is pretty much what you’ll find on all of the Virgin Islands, but the park is on St John, the smallest of the Virgin Islands which has pretty much got the best of everything.

The plentiful bays and islands have rocky outcrops which are fringed by coral reefs with their complex communities of marine animals and plants. The reefs are primarily made of hard corals including plenty of;

elkhorn
brain
finger
star
staghorn
plus soft corals like sea whips and sea fans

Of course, living amongst the corals is a whole community of fishes ranging from angel fish, parrot fish, snappers, grunts and surgeon. The renowned beaches of the area are completely dependent upon these reefs, for without that rich environment of living corals the beaches would simply not exist. The beautiful white sand of the beaches is actually made up of the tiniest fragments of the coral, as well as being protected by the coral from being washed away by the winter storms. In order for the corals to survive there is a delicate balance which must be maintained, the sea must remain;

pollution free
clear
constant salinity limits within around 30 to 36 parts per thousand
a steady temperature ranging from 21 degrees and 27 degrees C (or 70 – 80 degrees F)

Virgin Islands National Park Geology

Okay, enough about the sea, what about the geology of the actual islands? Unfortunately (or fortunately, whichever way you look at it) this has been drastically altered by us – well, not me personally, but men in general. The original plant and animal life is recovering slowly over some parts of the island.

In the protected valleys and northern slopes of the higher elevations you will find the subtropical moist forest. Unfortunately much of the forest was cleared years ago to make way for the sugar plantations, but slowly and surely it is returning.
Subtropical dry forests are found on the lower elevations, in particular the eastern and southern slopes, as well as the coastal sites which have less exposure.
The continual trade winds and exposure to the sun on the eastern and southern shores have made this landscape definitely more desert like, where you’ll find dildo, turks head cactus and opuntia.