Technology

One of the main compositions of the ocean floor is the seafloor sediments. There are four types of seafloor sediments according to composition lithogenous, biogenous, hydrogenous and cosmogenous.

Lithogenous sediments are the type of sediments derived from rocks. These are generally carried off to the ocean by wind, rivers, rainwater run-offs and water currents. Its sizes vary widely. Larger lithogenous sediments are heavy, sink faster, and thus, settle closer to lands. On the other hand, some of the smaller ones get carried out in the middle of the ocean because of its lightness.

Sediments obtained from living organisms are called biogenous sediments or oozes. Calcareous, siliceous and phosphatic are the three general kinds of biogenous sediments. Calcareous oozes are primarily consist of calcium carbonate shells and may form chalk upon settlement. Examples of calcareous organisms are cocoliths and foraminifera and they tend to be found in warm and tropical regions. Its distribution is greatly affected by the temperature of the ocean, population of microorganisms and mixing with lithogenous materials on sea floor. On the other hand, siliceous oozes are made out of silica shells. They are mostly cam from organisms like diatoms and radiolarian that mostly seen in polar and equatorial regions. Lastly, phosphatic sediments came from the teeth, bones and scales of fishes.

Hydrogenous sediments are derived from ions dissolved in the ocean that precipitates. These types of sediments are the less common than biogenous and lithogenous sediments. Its abundance is affected by change in temperature, change in pressure and addition of chemically active fluids. Types of hydrogenous sediments include ooids, evaporative salts and metal sulfides.

Cosmogenous are sediments that formed from materials from outer space. This includes cosmic dusts and unburned parts of meteorites. This kind of sediments is the least common and comprise only small fraction of ocean sediments.

Generally, biogenous and lithogenous sediments tend to dominate the ocean floor. However, its distribution is greatly affected by temperature and water depth. Calcareous type of biogenous sediments tends to accumulate in shallow, temperate regions because they dissolve in warm water slower. In contrast, siliceous type, which resides around the equator and in Polar Regions, dissolves slowly in cold water or in upwelling zones. Lastly, lithogenous sediments are most likely found in areas that are both deep and distant from land. An example of it will be the abyssal clay.

In many parts of the world, coastal erosion is becoming a large problem. To address to this problem, several techniques for preventing coastal erosion were devised. One of which is the so called French drain. It is a narrow trench filled with sand and gravel. The effectiveness of this technique is based on the amount of water that it can intercept. This technique provides a permanent solution to erosion. Another permanent but very practical method is allowing the natural vegetation of the shore undisturbed. The roots of the vegetation hold the soil and therefore minimize transport of sediments. Shore can also be protected from erosion by lining it with rocks. This technique is generally called rip-rapping.

Even though man can help in decreasing the rate of coastal erosion, some of mans works fasten the process. This is the case for the development of coastal areas. This development, such as roads, can increase the run-off of water by minimizing the contact between water and soil. Since grater run-off results to greater erosion, this action by man also increases coastal erosion. In some cases, the method used to decrease coastal erosion becomes the accelerator of erosion. This can happen to coast provided with walls. When waves collide with the wall, it becomes turbulent. This turbulence hastens erosion.