Jamaica is situated in the northwest part of the Caribbean Sea, one of the four of the Greater Antilles. Fringing reef systems extend over much of the north seashore, really of import natural ecosystems of Jamaica ( Goreau, 1992 ) , ( Moses, 2008 ) . To derive a greater a greater understanding these reef environments of the geology, hydrogeology and anthropogenetic land usage alterations regulating their formation and wellness must be evaluated. Through this study I will look to dissect these procedures from past and present happening within these coastal environments.
2. Major Geological characteristics of Jamaica
The island itself is split into two chief subdivisions. The E is dominated by the Blue Mountains, lifting to a tallness of 2,256 kilometer. This is separated from the West by a tableland of cretaceous crystalline and limestone outcrops, the Central Inlier ( Donovan, 2002 ) . The West is much flatter, lifting to a maximal tallness of approximately 900m and is largely composed of limestone, frequently referred to as the Cockpit Country ( Moses, 2008 ) .
Figure 1. Simplified geoligcal map of Jamaica, with perpendicular cross subdivision. Shows the laterality of the white limetone formations and the crystalline outcrops in the E ( Brown et al, 1973 ) .
The whole island was formed through four stages. First the cretaceous volcanic island discharge stage, followed by rifting of the discharge system in the Palaeocene to early Eocene. Following carbonates were immensely deposited in the in-between Eocene to Miocene. Finally distortion in the Cenozoic led to major upheaval making the Blue Mountain part in the West ( Mitchell, 2002 ) .
The Central Inlier is divided into four distinguishable subdivisions. The Arthurs Seat Formation is the oldest, composed of volcanic deposit and ill sorted pudding stones with sequences of irrupting butchs and little batholiths. This is overlain by the Crift Synthem composed of limestone. The Slippery Rock Formation is composed of pebble pudding stones, this is portion of the younger sedimentary sequence of the Kellites Synthem and third white and xanthous limestone groups. The concluding formations are the Guinea Corn Formation which is succeeded by the Summerfield Group. These consist of shoaling upwards Marine and volcaniclastic sedimentary stone ( Mitchell, 2002 ) , ( Mitchell 2005 ) .
Early on rifting continued throughout the Early Palaeogene, organizing extended block and trough topographies. Yellow and white limestone groups were deposited during the deep H2O and shallow H2O sequences within these blocks ( Mitchell, 2002 ) , ( Mitchell, 2005 ) .
Carbonates were deposited immensely over the border of the Clarendon Basin, within protected lagoonal environments ( Mitchell, 2005 ) . The major growing of coral environments ab initio started into the late Oligocene, shelf border environments supplying the place for extended reefs. The early Pleistocene was characterised by high clastic input in to the shallow coastal parts making unfavorable conditions. Regeneration occurred in the late Pliocene and early Pleistocene off from parts of high turbidness and deposit input ( Donovan, 2002 ) .
3. Hydrology of Jamaica
3.1 Karstic landscape
The hydrology of Jamaica is controlled by two chief factors ; the geology of the part, largely karstic formations, secondly the degree of precipitation throughout the twelvemonth ( Nkemdirim 1979 ) .
Karst parts have really characteristic hydrological characteristics, due to the ability of H2O to fade out the Ca carbonate of the limestone. This disintegration leads to the formation of extended belowground webs, leting surface rivers and watercourses to vanish into an belowground maze of caves and disintegration channels ( Fleurant, 2008 ) . These karstic formations dominate in the Cockpit Country of Jamaica, composed Eocene White Limestone formations ( Fleurant, 2008 ) . Cave, swallow hole and gorge formations occur throughout the part, another merchandise of huge disintegration of these limestone ‘s ( Donovan, 2002 ) . A big proportion of this H2O does n’t re-surface until these drainage webs reach the seashore. Submarine blowholes and surface crevices allow the fresh groundwater to resurface, frequently within embayment parts such as Discovery Bay ( Greenway, 2006 ) , ( Brown et al, 1973 ) .
Rain is besides improbably of import, imperative for the recharge of these karstic webs. Precipitation controls the recharge of the groundwater, regulating how much fresh water is discharged at the seashore. This fresh water provides the chief alimentary supply to the coastal embayment ‘s, hence is extremely influential on the biological productiveness of the reefs ( Greenway, 2006 ) .
There are two distinguishable moistures and dry periods throughout the twelvemonth in Jamaica. The first wet period occurs in May, with 167mm of precipitation on mean falling over the month, the 2nd in October, with 166mm of rainfall falling. The dry seasons fall between the months of February to April, and the 2nd from June to August, with between 57-91mm over each month severally ( Creary, 2012 ) . The Blue Mountain parts tend to have significantly more rainfall than the remainder of Jamaica, around 7.5mm of precipitation falls over the class of the twelvemonth ( Berglund & A ; Johanson, 2004 ) .
It ‘s of import to indicate out that the rainfall over the twelvemonth is improbably variable, rainfall forms may non needfully conform to these moistures and dry seasons ( Greenway, 2006 ) .
Figure 3. Relationship between rainfall and overflow within Jamaica, shows the high importance of rainfall ( Nkedirim, 1979
Figure 2. Mean monthly upper limit and minimal air temperature and rainfall within Discovery Bay, over ( ? ) ( Creary, 2012 )
4.Bauxite excavation and deforestation
Aluminum is one of the universe ‘s most of import metals. In the signifier of its ore, bauxite, it is found in important measures within Jamaica. The bauxite industry is improbably of import for the Jamaican economic system, doing up about 20 % of the state ‘s entire income ( Moses, 2008 ) . As of 2004 merely Australia and Guinea produced more bauxite than Jamaica ( Berglund & A ; Johanson, 2004 ) .
Throughout the island there ‘s thought to be over 1.8 billion metric tons of bauxite, of which 1 billion metric tons is able to be accessed with comparative easiness ( Berglund & A ; Johanson, 2004 ) . Most of these sedimentations reside in the White Limestone Groups in the cardinal tableland part ( Grant et Al, 2005 ) , where crisp basal contacts occur ( Donovan, 2002 ) .
There are three chief theories to why these bauxite sedimentations have formed within Jamaica. The ‘Residual Theory ‘ , secondly the ‘Alluvial Theory, but it ‘s the 3rd theory, ‘the Volcanic Ash Theory ‘ that ‘s now by and large accepted. Here bauxite is thought to hold formed through the weathering of pyrogenic stones formed during the eruptions in the Cenozoic which was deposited on the top of the karstic limestone ( Donovan, 2002 ) .
Although economically of import, the bauxite excavation has some serious deductions on the Jamaican environment. The excavation processes involve the extended remotion of dirt to make unfastened dramatis personae mines so the bauxite can be easy accessed. The dirt that ‘s removed is replaced after the completion of the excavation. However the belongingss of this dirt are frequently extremely affected, with local flora agony as H2O keeping is hapless ( Berglund & A ; Johanson, 2004 ) .
Deforestation is besides a major job. It ‘s necessary to take important measures of local wood to do manner for new entree roads to the excavation country. This does n’t merely take to the devastation of local home grounds, but the big extent of this deforestation may be changing the hydrosphere of the part. Consequently it ‘s proposed an addition in unnatural rainfall forms and more terrible checkerss could be happening ( Berglund & A ; Johanson, 2004 ) .
Figure 4. Major land usage alterations between 1989 to 1998, showining major forest alteration, and big addition in bauxite excavation ( Berglund & A ; Johanson, 2004 )
5. Hydrography of the northern Jamaican Waters
Jamaica is dominated by North East Trade Winds, chiefly due to both the alleviation of the island and its latitude. In general these air currents will stay unagitated throughout the dark ( Gayle & A ; Woodley, 1998 ) . At around 09.30am the air currents begin to pick up as the solar warming additions. This steady sea zephyr remains changeless throughout the twenty-four hours, lessening at around 6p.m. as the temperatures cool ( Moses, 2008 ) .
Figure 5. Change in air current velocity throughout the twenty-four hours within Discovery Bay Jamaica, shows clear tendency of increasing air current velocities throughout daylight hours, get downing around 9pm and decreasing about 6pm ( Genovese & A ; Witman, 2004 )
5.2.1 Caribbean currents
There are several strong currents and ocean coil systems environing Jamaica and the Caribbean.
There are three chief currents, these include ; the Yucatan Current, the Loop Current and the Florida Current. The chief coil is found in the Columbian Basin, which is cyclonal in nature. This cyclonal coil creates ‘drifter ‘ currents, which move North West over the Jamaican Ridge. This transition of H2O consequences in the formation of two strong jokes which leads to the formation of the Yucatan Current ( Centurioni & A ; Niiler, 2003 ) .
In Northern Jamaica, wave action is largely low due to the protection of the fringing reefs, with currents fluxing in a western way ( Wade, 1991 ) , ( Brucks, 1971 ) .
5.2.2 Discovery Bay currents
Embayment ‘s seem to hold their ain current circulation system, chiefly controlled by air current forms, therefore are outstanding during the daylight. This becomes evident as flow rates in the back reef during the twenty-four hours are larger than those during the dark. Two cardinal forces act upon the currents, the Waterss move from E to west within the bay through the force of the Caribbean western currents, whilst the trade winds create moving ridges which travel into the bay from the nor’-east. These two coercing create round currents that rotate clockwise within the bay itself ( Genovese & A ; Witman, 2004 ) .
Figure 6. Major ocean currents environing the Jamaican coastline, shows the laterality of western surface currents ( Goreau, 1992 )
Sediment conveyance within Northern Jamaican coastal parts is chiefly controlled by the currents plus the influx within the coastal embayments. The trade air currents and western currents making the clockwise currents within the bay can frequently re-suspend the deposit within the bay when they are strong ( Gayle & A ; Woodley, 1998 ) . However Discovery Bay has no fluvial input, hence no terrigenous deposit supply other than from wind-blown beginnings from off of land and the bauxite burden works in the West of the bay. This leads to press, manganese and aluminium rich stuff in the West corner of the bay, peculiarly through wind-blown deposit. Hotspots of bauxite accumulate in the North East and North West of the loading terminus ( Perry et al, 2006 ) .
Jamaica dominated by White Limestone formations formed in the Tertiary, doing up the big karstic formations of the cockpit state in the West, whilst higher, older crystalline stones dominate the E with the Blue Mountains ( Donovan, 2002 ) .
Hydrology of Jamaica shows characteristic karst groundwater flow ( Fleurant, 2008 ) , with over 80 % ( ECLA ) of human supply coming from these beginnings. Degree of groundwater escape is controlled by the degree of precipitation, which tends to re-submerge at the coastal embayment webs ( Greenway, 2006 ) .
Bauxite excavation is the chief industrial procedures within Jamaica, lending to over 20 % of the state ‘s entire income ( Moses, 2008 ) . This has led to deforestation within the state, overall there has been over a 50 % decrease in forested countries ( Berglund & A ; Johanson, 2004 ) .
The Trade winds rule throughout the island, winds pick up along the seashore in the late forenoon and last until 6pm ( Moses, 2008 ) .
Main currents ruling Caribbean Waterss are the Yucatan Current, the Loop Current and the Florida Current, including a cyclonal coil found in the Columbian Basin ( Centurioni & A ; Niiler, 2003 ) . The north seashore is dominated by western currents, where the fringing reefs protect the seashore from buffeting moving ridges ( Genovese & A ; Witman, 2004 ) .
Sediment conveyance follows the chief current flows, with industrial bauxite activity act uponing the deposit lading within Discovery Bay itself ( Perry et al, 2006 ) .