Hol Chan Marine Reserve

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Chapter 3. SITE DESCRIPTION

a - General features of the site

Terrestrial surface under sovereignty, excluding wetlands:

0 sq. km

Wetland surface:

900 ha

Marine surface:

42 sq. km

b - Physical features

Brief description of the main physical characteristics in the area:

See items below

Geology:

Geological Aspects: The Belize Shelf is divided into distinct northern and southern halves. Its edge is characterized by a series of five discontinuous rides that trend northeast and which are thought to be fault controlled. The least defined ridge lies along the northern edge of the barrier reef and Ambergris Caye, encompassing the Hol Chan area. (James and Ginsburg 1979). The Belize Shelf is the drowned expression of a low-relief karst surface, on which sinkholes have locally developed (Mazullo and Reid 1985). Examples of these can be seen in the channels of the Boca Chica area, which probably represent drowned river channels or solution beds, and the Boca Ciega ‘Blue hole” which is a collapsed sink hole. This sinkhole opens into a large cavern, the extent of which has not been fully explored.

Soil:

Processes of sedimentation and erosion: Average depth at the reef lagoon is three meters and is not greater than 5.5 meters. The reef edge occupies a narrow strip on the seaward edge of the shelf. On the leeward side of the reef crest, debris accumulates in the reef lagoon as slightly muddy skeletal sand which is stabilized by beds of sea grass. (Miller and Macintyre 1997).

Topography:

Coastal Geomorphology: Coastal geomorphology is dominated by the Boca Chica and the Cangrejo shoals mudbanks and is located in the southern tip of Ambergris Caye. The shoals cover and area of 12 square kilometers and is composed of 6.7 meters thick of unconsolidated carbonate sediments deposited in a large depression of karsted Pleistocene limestone (Teal 1998). The shoal is dominated by Red Mangrove ( Rizophora mangle ) thickets but they have not trapped enough sediments to form land for Cayo Rombo and Cayo Cangrejo where supratidal flats are present.

Hydrodynamics:

Main water courses (permanent and seasonal): Freshwater drains from the mainland into northern Chetumal Bay and drains southwards along the leeward side of Ambergris Caye.

Underwater formations:

The Barrier reef is the main feature of interest in the marine Reserve. There are approximately 5 kilometers square of coral reef including the main barrier reef and deep fore reef area. The Boca Ciega ‘Blue Hole’ is a collapsed sinkhole that lead into a large underwater cavern which has not been fully explored.