THE CREATION OF
BISCAYNE BAY
he fractious interplay of rock and water, acted out in the distant and recent past, has created the Biscayne we see today. The park is located on the southern Florida peninsula, which is very low and flat because it was once an ancient sea bottom. Not including the Calusa shell mounds, the highest point in the Everglades is just 10 feet above sea level. The bedrock of the area is limestone, which is made up of marine sedimentary rock. The contraction and expansion of continental glaciers have altered the landscape. The Florida peninsula has been inundated by and later emerged from the surrounding seas at least four times in recent geologic history. As glaciers expanded, they consumed bodies of water, including the shallow tropical seas covering Florida, causing the land to emerge. Then, as they melted, the seas returned, submerging the Florida peninsula.
Each time the glaciers melted and the seas returned, the water level was lowered because much of the land mass was slowly rising. The lower areas of Florida, however, still held water, creating inland lakes such as enormous Lake Okeechobee.
During the interglacial periods when the land was underwater, millions of plants and animals decomposed and deposited calcium carbonate onto the sea floor. This calcium carbonate accumulated around grains of sand and hardened into oolites, called "egg-stone" because when examined closely, the granules resemble a mass of tiny fish eggs. Limestone composed of oolites is very porous and spongelike. Today, this oolitic limestone forms the gently sloping bedrock of the Everglades.
The foundation for the Florida Keys was laid 100,000 years ago by billions of tiny coral animals. Eventually this multitude of workers created a 150-mile-long chain of underwater coral reefs. As the land mass of southern Florida began its slow rise from the sea, the reefs also began to emerge. What resulted were the many islands of the Florida Keys, constructed mainly of fossilized coral rock. You will see these keys in Biscayne Bay.
2006-09-07 13:57:25
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answer #1
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answered by odu83 7
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