Change in the Relief of South Florida

Over the course of time, the earth’s landforms have gradually changed to the form they are today, both the continent and local regions. South Florida is no exception and its landform has changed over geological time. According to the publication Florida’s Geological History of Ginger M. Allen and Martin B. Main (2005:2), the main geological factors that contributed to shaping Florida’s current landform are alterations in sea level that therefore changed Florida’s bedrock. This affected other environmental features, such as soil and surface topography.

The Florida plateau, as Allen and Main call it, was formed 530 million years ago (to earth’s 4.5 billion years) by volcanic activity and marine sedimentation. As Pangea, Florida was stuck between what would be North America, South America, and Africa (Allen and Main 2005:1). According to the theory of plate tectonics, the lithosphere contains 12 plates that move over the asthenosphere. A plate can contain land and oceanic crust; the North American plate, which is where Florida is situated, contains North America and some, if not the majority, of the Atlantic Ocean.

Hence, when Pangea began separating, the Florida plateau moved with the rest of North America into Laurasia, rather than southern Gondwana (Allen and Main 2005:1). Since then, tectonic forces, such as diastrophism or volcanism, has not really affected Florida. It is not near fault lines.

Allen and Main (2005:1) indicate that a massive migration of plants and animals commenced 2 million years ago, citing that sea levels were low enough that there was a land bridge between North and South America, therefore allowing this passage.

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According to lower sea levels, there was more exposed land mass, three times the size there is today. Furthermore, Allen and Main (2005:1) state that conditions were drier through the previous ice age, demonstrating conditions similar to a savanna climate. This signifies that Florida was a tropical grassland with widely dispersed trees, and experienced significant wet and dry seasons. This foliage supported animals that were able to eat the sort of flora available at the time.

Nearing the end of the latter ice age, 10,000-12,000, Paleoindians reached Florida (Allen and Main 2005:1). Therefore, the extinction of several species there could have been caused by Paleoindians; that, and changing weather conditions resulting from the conclusion of that ice age. Sea levels rose again due to rising temperatures (Allen and Main 2005:1), which then resulted in continental ice glaciers melting, therefore cutting off the previous land bridge and covering most of the existing land mass, rendering it into a smaller peninsula. The landscape grew wetter, hence resembling more of the humid subtropical climate, it is today, with hot summers and mild winters (both moist). The Everglades were also formed by rising sea levels around 4,000-6,000 years ago (Allen and Main, 2005:1).

Allen and Main then describe how the rising sea levels affected Florida’s soil. Now submerged, the landforms that were once above water eroded away by the incoming waves. Additionally, the currents deposited sediment, hence contributing to Florida’s modern landform (Allen and Main 2005:2). Slow-moving original agents were most likely responsible for dropping sediment on the submerged landform. The submerged land, hence acted as a location for the calcium carbonate remnants of sea creatures and algae (Allen and Main 2005:2). The existing material was compressed by the incoming weight of new materials, and with the chemical action of water and certain minerals, layers were created and formed sedimentary rock, specifically limestone. The erosion of that limestone bedrock formed coast landscape in many regions of Florida, therefore leading to sinkholes, underground caverns and/or streams, etc.

Running water, another major original agent, and ocean currents deposited large amount of sediment, such as quartz and other minerals, originates from the Appalachians (Allen and Main 2005:2). The amount of deposit would also have aided in creating the sedimentary limestone bedrock.

The process of erosion and depositing created Florida’s lowlands and highlands. Northern and central Florida is mainly highlands, while southern and coastal Florida is mainly lowlands. South Florida is characterized by low-lying lowlands (Allen and Main 2005:2).

Therefore, South Florida has, indeed, mainly been shaped by rising sea levels which enabled erosional forces to create the predominant sedimentary limestone bedrock. Its position on the North American plate, relatively far from fault lines, allows South Florida to remain as flat lowlands.