Soil Horizon - Assignment Example

Definitions Full Definitions Soil Horizon A Soil Horizon is a layer of soil which is parallel to the current soil surface. They represent different surfaces of soil over a period of time. They are visible and characterized by different texture or physical features as a result of soil deposited over an extended period of time. Different layers can be distinguished by their colors. In simple they are layers of soil deposited that present historical account of surface conditions in the past. These layers become different and represent the older soil materials over time and give an idea of how the soil of a particular area was as compared to different periods. Mechanical Weathering Mechanical Weathering is the cutting or reshaping of the surface done by the Earth’s atmospheric elements (Monroe & Wicander, 2012, p.137). This breaking down process is caused by physical contact with the atmospheric elements which include heat, water and pressure. For example rocks can be disintegrated by simply expansion and contraction by change in atmospheric temperature. Similarly the surface can be damaged with the change in pressure. In any surface the layers below are under pressure by the weight of the surface above. In case of erosion when the higher surfaces change, pressure is decreased and different surfaces tend to expand under the conditions of changed pressure. Therefore, expanding and exerting pressure on parallel surfaces under new pressure conditions. Chemical Weathering Changes done to the surface when atmospheric elements carrying chemical agents come in contact with the surface. Acid rain is one example of these elements and contains sulfuric acid. When it comes in contact with rocks the chemical reaction changes composition in some cases and causes weathering. Spheroidal Weathering Spheroidal Weathering is a form of Chemical Weathering in which the larger rocks form rounded shape. In simple the weathering in this case takes away the joints and edges of large blocks as they are more exposed to atmospheric elements. Water creeps into cracks and edges and they are taken off the surface gradually. Round surface is formed which presents an equal area exposed to atmospheric elements. Leaching Leaching is the process in which minerals in top layer of the soil are mixed with water and are carried to lower layers as the water seeps into the surface. Many valuable nutrients are absorbed by water and are deposited in lower layers, whereas, the non-soluble materials remain on the top surface. Creep Creep is the deformation or disintegration of materials after being exposed to external stresses for a long period of time. This effect increases with increase in magnitude of stresses. Heat and pressure are the main stresses and their magnitude is proportional to the effect. Landslide Movement of the large portion of ground that becomes unstable. The ground slides down with gravity. Earthquakes are one factor to initiate the movement, however, other factors include amount of groundwater and erosion in the particular area. Deforestation is also a contributing factor as the trees provide stability against slides and supports the slide surfaces against weakening. Permafrost It is the permanent freezing of soil or sediment. This happens when the surface is in sub zero temperature for more than two years (Harris & Murton, 2005, p.11). The phenomenon may even take place in layers below the active surface. The active layers in extreme cases are on top of a permanently frozen surface or in simple permafrost layers. These layers are found typically in the poles or areas with extreme cold weather, where temperature remains subzero throughout the year. Solifluction The downward movement of highly saturated soil above waterlogged surface. The movement typically takes place in areas with temperature range near zero degrees Centigrade. Ice forms and melts in this temperature range, therefore, absorbing soil content. Furthermore, waterlogged areas favor this effect as the water content is high and the soil saturates. Talus The deposits of defragmented rocks at the base of mountains are known as Talus. These may be formed by mechanical or chemical weathering. Erosion also plays an important part to break up rocks or mountains. Stream Divide A Stream Divide is the division of a stream in two separate streams. This typically happens on a high point or a ridge. The height of the point determines whether the water will flow in one way or another. Stream Piracy The process when a stream changes its original flow bed with a neighboring bed. This change can be due to the movement of Tectonic Plates, changing the slope of the surface or erosion of the original stream into another bed. In simple it is the change in direction of a stream or a river. Dendritic Drainage Different streams collect and contribute their share in the river or the main stream. Water is collected by these streams and forms an intricate web of streams across the area. The pattern they form is like a tree (Jain, 2007, p.14). The river is the main trunk, whereas, the streams can be represented by the branches of a tree. They are distributed at various angles and patterns and depend on the undulating surface level of the area. Parallel Drainage The streams run parallel to the main river in this case of drainage system. This is caused by steep slopes where the streams are supported by gravity to form straight beds along the river. This pattern is different than Dendritic Drainage as the pattern is usually parallel along the main stream instead of horizontal or haphazard. Trellis Drainage The drainage pattern in this case is formed in a trellis or in simple parallel and perpendicular streams contribute towards the main river (Jain, 2007, p.14). This pattern is usually formed in deep valleys or high mountains with straight passages and gaps. Dissolved Load It is the amount of ions which are the byproduct of chemical weathering dissolved or included in the stream. The amount of these materials changes the chemistry and composition of the stream, since ions are involved in breaking and forming new compositions within the main flow. They are also responsible for chemical changes in materials in contact with the stream. Natural Levee Natural Levees are naturally formed embankments along the stream or river (Evans, 2005, p.10). They regulate the water level and run along the stream. They are formed and reinforced during floods as the river expands and slows down; it deposits sediments which form embankments or levees. This process when repeated over time raises the level of these levees. Suspended Load It is the amount of sediments carried by a stream or a river. These sediments are the byproduct of weathering and include fine particles like sand, silt and clay. Because of their fine size they are suspended in the stream and settle slowly as sediments when the flow is slow enough for these particles to be deposited on the river bed. The Suspended Load is different than Dissolved Load in a way that these particles or sediments do not change the chemical composition of the stream and their properties remain the same. They are also the major sediments carried by the river. Meander Cutoff Meanders form when the river flows in a wide area of the valley and form curves or bends. When the flow is strong in a stream the closest gap in the meanders are cutoff and water takes the shortest route. This causes the water to abandon the meander. This cutoff can be the result of flooding. Once the flow is regularized the stream may completely abandon the meander and take the newly formed path permanently. Ultimate Base Level A Base Level is the lowest point to which the river can flow. It terminates at this level. However, the major rivers end up at the sea and the sea level is the lowest possible point to which any river can flow. The sea level is therefore, known as the Ultimate Base Level. References Evans, G. (2005). Flood Risk Assessment. Exeter: Short Run Press. Harris, C., & Murton, J. (Eds.). (2005). Cryospheric Systems: Glaciers and Permafrost. Massachusetts, MA: The Geological Society. Jain, R. (2007). Geography 10. New Delhi: Ratna Sagar. Monroe, J., & Wicander, R. (2012). The Changing Earth: Exploring Geology and Evolution. (6th ed.). California, CA: Brooks/Cole. Read More