Geology students and professors from Wichita State University and Oklahoma State University at Rocky (Reef) Point in August, 1998 in the first photo below. The Pleistocene limestone that is exposed here, in the foreground of the photo, is about 125,000 years old and is a fossil reef that contains the same kinds of corals as in the modern barrier reef. Notice the grassy area and heavy vegetation behind the students, at the edge of the jungle.
The next photo shows Rocky (Reef) Point after Mitch. The Pleistocene limestone is now exposed more because much of the grass was stripped off by Mitch; the remaining grass is dead, killed by salt water. Where there was vegetation along the edge of the jungle prior to Mitch, there is now about 2 feet of new beach sand.
This is "Turtle Beach" immediately north of Rocky (Reef) Point after Mitch. The storm caused about 1-2 feet of vertical erosion along the seaward side of the beach, exposing once-buried Pleistocene coral reef limestone. The sand from here was transported landward and redeposited on top of the older beach surface, making a new, higher and wider beach in a geologically constructive process of "vertical and lateral beach accretion". The geologists are, of course, studying the newly exposed limestones. |
From reports from the island, and what we saw on our survey, there was relatively little storm damage/change to the back-reef (immediately behind the reef crest, which is marked by the line of breakers along the reef) and outer-shelf lagoon. We noted that most of the sea fans (gorgonians), sponges, and stalked green algae (like Halimeda and Penicillus) had been uprooted from along the back-reef and transported inland. In fact, many of the beaches along the caye are littered with them. The green algae are mostly gone from large areas of the outer-shelf, but being fast-growing organisms they should recolonize the area quickly. Shark & Ray Alley received a new layer of white sand that mostly buried the former grass (Thalassia) beds there, but the grass will come back all too quickly. The following photos illustrate some of the damage/change that we saw in the back-reef.
The first photo shows one of our geology student groups at what we call the "Dredge Site", which is a little island along the reef between the Hol Chan Marine Reserve cut and Shark & Ray Alley. The island was about 100 feet long and a maximum of about 5 feet high prior to Mitch. It was a favorite stopping-off point for a refreshing dip in the sea after a long day in the swamps. The highest point on the little island was made of huge boulders of reef limestone.
The next photo shows what remains of the Dredge Site after Mitch, at dead low tide! None of the huge limestone boulders remain. The island would be barely visible at normal high tide. The sea giveth and the sea taketh.
The first photo is a view of the back-reef on the south side of the Dredge Site taken before Mitch. The brownish corals in the right-center of the photo are star corals (Montastrea annularis), and the smaller green corals in the center of the photo and elsewhere are the coral Porites astreoides.
In the next photo below, after Mitch, although the Montastrea patch is out of the field of view it had been seriously broken down by the storm. Note that the abundant Porites that were present here before Mitch are now gone (washed away and buried under the rubble). The entire bottom is carpeted by fleshy algae (light colored, bush-like plants), and large fragments of the elkhorn coral Acropora palmata (center foreground) that were broken from the reef crest and redeposited here. The good news is that new coral growths were readily obvious in our snorkeling survey here.
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