What is a Barrier Island - Essay Example

? 8 Apr. What is a barrier island? The concept: Conventionally, barriers are understood as objects that play the role of blocking something or hindering the passage or flow of something. On the other hand, an island is a land area that is surrounded on all sides with water. Therefore, combining both words, “barrier island” is essentially a piece of land which provides the coastline with protection against the damages of storms and cyclones, and also offers a habitat to the wildlife along with the protection. Any place that is equipped by animals and plants of different sorts and can provide them with all necessities of survival classifies as a habitat. It is normally a thin and elongated area of land that is largely made up of sand. Habitat: Barrier islands are located on the North American eastern coast in such places as North Carolina, New Jersey and Florida. Some barrier islands are also situated along the gulf coast, i.e. Louisiana. Different components of a typical barrier island include but are not limited to dunes, salt marshes, oceans, mainlands, backdunes and bays. A dune is a hilly area made up of sand brought with the passage of wind. Backdune, as the name implies, forms that rear part of a dune. When salt water overflows somewhere, flat pieces of land emerge that are known as salt marshes. Small bodies of water that are distant from the main water body with a large volume are known as bays. All of these places provide different types of organisms with habitat. Organisms like spiders, fish and egg laying animals usually occupy the regions in vicinity of the dunes or oceans. Some of the most common animals that live on the beaches of the barrier islands are seagulls, burrowing worms, pelicans and scavenging crabs. Different kinds of terns and crabs live in the dunes. The number of organisms living in a barrier island depends upon its size. In large barrier islands, there are more habitats to accommodate more organisms. Likewise, smaller islands offer fewer habitats for lesser animals. Weather conditions in the barrier islands: Barrier islands have harsh conditions. There are frequent speedy wind blows and sand blows that result into extreme dryness. The coastal storms are so powerful and full of energy that they can totally ruin the barrier islands. They are empowered by such features of the natural environment on the barrier islands as high tides and waves. The constant change in the weather conditions causes an equivalent change in the habitat. The animals that live there have adapted themselves to survive in extreme conditions accordingly. Likewise, the human population that lives on the barrier islands is also equipped with the required necessities to combat the extremity of weather. Most people who live in the barrier islands at a certain point in time do not occupy them permanently. People construct homes on them to use them temporarily as they spend their time on the barrier islands during summer vacations. Effects of storms on the barrier islands: Along with affecting the animals and humans, the coastal storms also have a severe impact on the form and shape of the barrier islands. A lot of erosion occurs on the dunes when coastal storms occur. Severe forms of coastal storms can fully damage the dune system. The power of the coastal storms can be estimated from the fact that just one storm can disintegrate all components of a barrier island and completely wash it away. Barrier islands may disappear as a result, though it only takes one to two years for a lost barrier island to resurface. Originally, the deterioration of an island is not physically noticeable. But the currents of wave increase in their size and energy level when the island is actually gone. Summary of the concept: A barrier island is a region that is largely made up of sand and its function is to serve as a barrier between the coastal storms and the mainland. In an attempt to save the mainland, barrier islands frequently encounter storms as a result of which, animals and people living on them have to face severe repercussions. Therefore, it is not quite advisable for people to construct homes on the barrier islands, though home on a barrier island is a dream of many people because of the extreme natural beauty of the environment. Barrier islands make very good tourist attractions. Examples of barrier islands: Cape Cod: Cape Cod situated in Massachusetts can not typically be referred to as a barrier island, though it has many features in common with a barrier island. Like a typical barrier island, it is a peninsula which provides Massachusetts with protection against the aggressive coastal storms. Cape Cod is also similar to a barrier island in terms of sections and the types and population of organisms that live in it. Keewaydin Island: Situated on the Gulf of Mexico, the Keewaydin Island in Florida makes it way through the midline between Marco Island and the Naples Island. It is a barrier island which goes across the western coast of Florida up to 300 km (Yale). Other examples: Example of a barrier island that first washed away and then resurfaced after one to two years is the Raccoon Island situated in Louisiana. Example of weather conditions that caused severe damage to a barrier island is the “hurricane Andrew in Louisiana” that caused the Isles Dernieres to loose up to three of the ten portions of the island (Paris). Example of damage of a barrier island caused by the coastal storm: The hurricane in Ocean City: Ocean City in Maryland and Boston Harbor in Massachusetts are typical examples of barrier islands. Despite being attacked by coastal storms a lot of times in the past, Ocean City still qualifies as a wonderful beach resort and attracts thousands of tourists every year. Ash Wednesday northeaster was the biggest storm that attacked the Ocean City in March of 1962 (Paris). The storm completely flooded the Ocean City. Waves distorted the boardwalk. The excessive water flooded the basements and ground floors of hotels. Occupants of the buildings became completely helpless and hopeless as they had to spend full four days without electricity. A lot of homes that were constructed in the Ocean City were damaged as a result of the storm. The geological history and geological structure of barrier islands: Waves, tides and winds which erode, blow, transport and deposit the sand particles and sediments give rise to a dynamic system upon interaction with one another. Such a dynamic system is known as a barrier island (Leatherman). In a geological language, most of the barrier islands are quite young, and not many are older than 7000 years. In fact, the age of a vast majority of the barrier islands is even less than 3000 years (“NOAA Coastal Services Center”). Barrier islands are formed with the interaction of sediment, waves and changes in the sea level. Barrier islands require the depth of water to remain unchanged in order to develop. This allows the wave action sufficient time to pile the sand up to form the barrier islands. Time taken by a barrier island to form is determined by the rate of alteration of the sea level and the sand available. The following figure shows that there have been rapid changes in the sea level in the past up till 7000 years ago, when the sea level became relatively unchanged and the barrier islands started to develop. “Sea level curves over the past 35,000 years (upper). Three sea level curves for the late Holocene Age (past 8,000 years) (lower)” (“NOAA Coastal Services Center”). Barrier islands can be classified into three types depending upon the sediments and Holocene processes that determine their geological structure: Simple overwash barrier islands: Simple overwash barrier island is the type of barrier island that is poor in sediment content. These barrier islands are inlet dominated. These barrier islands are generally deep and elongated in form. They have transgressive shorefaces. “The minor amounts of sand generally overly compact estuarine peat and mud deposits or sand-filled channel deposits that extend from the modern estuary, under the barrier sand, and crop out within the surf zone and upper shoreface” (Mallinson et al.). Simple overwash-dominated barrier islands: These barrier islands are rich in sand. The overwash plains are extensively built from the large sediment volumes. The overwash plains are normally made up of different orders of swale and low ridge structures. As a result of that, a regressive shoreface is formed that comprises unconsolidated sand. Progradational geometries dominate in this type of barrier islands. Complex barrier islands: The union of a simple segment of barrier island into an older segment which was created under different conditions gives rise to the complex barrier islands. How did the barrier islands form and what evidence is used to support this interpretation? Theories for the formation of barrier islands: Three theories have been put forward to explain the process of formation of the barrier islands. The first theory explains the role of waves in the formation of a barrier island. Waves on the shallow water along the mainland shoreline deposit sand landwards with great energy. As the process happens repeatedly and frequently, more and more sand piles up and gradually develops a whole sand bar. Once the sand bar approaches the level of the sea in crest, the approaching sea waves are then broken by the top of the sand bar. Thus, the sand bar takes time to develop. First, it forms in the intertidal zone. With the passage of time, it supersedes the level of the high tide. If no storms occur for a significant period of time, the sand bar catches vegetation and becomes an island. It is this vegetation that entraps more sand which is required in the formation of sand dunes that grow larger as time passes. On various places alongside the Gulf Coast of Florida, many barrier islands have formed in few years. This serves as an evidence to support the first theory of formation of the barrier islands. According to the second theory of the formation of barrier islands, the barrier islands were once the part of mainland adjacent to them. Enormous storms that occurred from time to time separated the narrow sand accumulations from the mainland, thus forming the barrier islands. Evidence to support the second theory of formation of the barrier islands is the hurricanes that frequently keep breaching the mainland in the Gulf Coast. The third theory of the formation of barrier islands suggests that they are formed by the dunes that are on the low lying coastline as the sea level rises. Flooding of the coastal regions caused the dunes to rise up and create long and narrow islands. With the passage of time, the rising sea water separated the islands from the mainland, thus creating the barrier islands. This theory presents a reasonable way in which barrier islands may form, though there is little to no evidence to support the third theory of formation of barrier islands. What role do barrier islands play in the shoreline ecosystem? Their role of absorbers of the shocks generated by the high-energy marine systems allows them to minimize the erosion in the mainland coast. Barrier islands provide shelter to the coastal habitat, and are hence, necessary for the sustainability of a lot of ecosystems that include but are not limited to lagoons and estuaries. Such ecosystems are the fundamental source of food and energy for both the flora and fauna. The following text discusses one such barrier island that plays a role in the protection of shoreline ecosystem: Protection of the Mangrove Estuaries in North America: Keewaydin Island in Florida is “the outermost barrier of the Rookery Bay National Estuarine Research Reserve (RBNERR), located northwest of the Ten Thousand Islands and the Everglades National Park” (Novakowski). The RBNERR serves as a barrier between the coastal storms and one of the biggest and lengthiest mangrove estuaries which can be found in the North America. How do barrier islands change over time? Sea level is constantly rising because of the global warming. The glaciers are melting away and adding to the water in the sea. The rise in sea level causes the transgressive barrier islands to move towards the nearby mainland. The migration of barrier islands can be attributed to the constant erosion of the front portion of the islands caused by the action of the sea waves. The sand on the front side easily erodes away because these islands lack in thick and dense vegetation that would anchor the soil with the roots of the plants. The lack of reinforcement saps the sand’s capacity to survive through the wave action, and the side exposed to sea waves erodes away. The waves thus take the sediments from sand dunes and beaches and deposit them on the rear side of the barrier island. Also, during aggressive storms, ocean waves flood the island, thus depositing the sand in the form of washover fans on the backside of the dunes. The enormous pileup of the washover sand grows the backside of the barrier islands and they ultimately migrate towards the adjacent mainland. The following figure explains the process: Wave action on the barrier islands causing them to move towards the mainland (“Barrier Island Processes”). What sorts of environmental concerns do shoreline development and human use create for barrier island systems? Humans greatly impact the barrier island systems in a number of ways. Evolution of a barrier island is just as influenced by such factors as cultural diversity, world politics and economics as it is affected by the diversity of weather that prevails in its location (Stutz and Pilkey). The roads, jetties and bridges constructed by humans alter the direction of water flow which, in turn, affects the method of deposition of sand on the beach of the barrier island. The natural beauty of the barrier islands appeals people to construct homes on them for spending vacations. “Permanent changes are made to the barrier flats and salt marshes to accommodate the building of homes, businesses, and infrastructure” (“Science and Environment”). Three inherent characteristics of the barrier islands are affected by humans. First, the “local” activity of humans affects the unique ecological and physical properties of every barrier island. Secondly, the “regional” activity of humans impacts the link between islands that are chained with the long shore transport and thirdly, the stabilization along shoreline together with the regional activity affects the barrier island’s ability to react to change of the environment through the cross shore transport. The term used for the resistibility of the barrier islands to the environmental impacts of the activities of humans is the “geomorphic carrying capacity”. “Geomorphic risk factors serve as a basis for predicting resiliency, providing both a measure of dynamic change (erosion rate and storm frequency) and available buffer space (island width and elevation)” (Stutz and Pilkey). Increase in the frequency and severity of the risk factors causes the barrier islands to alter as both the dynamic and spatial properties of a barrier island become inconsistent with the elements of the human landscape. Works Cited: “Barrier Island Processes.” n.d. Web. 7 Apr. 2011. . “Beach Nourishment: A Guide for Local Government Officials.” NOAA Coastal Service Center. n.d. Web. 8 Apr. 2011. . Leatherman, Stephen P. Barrier island handbook. Maryland: University of Maryland, 1982. Print. Mallinson, David J., Riggs, Stanley R., Culver, Stephen J., and Ames, Dorothea. “The North Carolina Outer Banks Barrier Islands: A Field Trip Guide To The Geology, Geomorphology, And Processes.” East Carolina University. n.d. Web. 8 Apr. 2011. Novakowski, Karyn I. “Barrier Island Accretion and Geomorphological Evolution of Keewaydin Island, Collier County, Florida.” Franklin and Marshall College. n.d. Web. 7 Apr. 2011. . Paris, Natasha. “Barrier Islands What?” n.d. Web. 7 Apr. 2011. . “Science and Environment: How Barrier Islands Work.” 2010. Web. 8 Apr. 2011. . Stutz, Matthew L., and Pilkey, Orrin H. “The relative influence of humans on barrier islands: Humans versus geomorphology.” Geological Society of America. 2005. Yale, Kristin E. “Regional stratigraphy and geologic history of barrier islands, west central coast of Florida.” Master’s Thesis. University of South Florida. 1997. Read More