The Natural Landscapes - Essay Example

Physical Geology Physical Geology Wherever we go in the world, the one thing above all others that will be unique is the natural landscapes. Everymountain, forest, desert, river, valley and ocean has its different characteristics and make-up. In fact, if we travel across the globe, we will find that no two landscapes offer same view or construction. It is fascinating to understand how the natural environment has developed, and what forces of nature have shaped the environment that we live in and the landscapes we tend to take for granted. The earth has evolved over billions of years. From a global mass of matter has been created the beautiful, picturesque, but sometimes savage and rugged landscape that we now enjoy. If we were to look at a cross-sectional view of the earth, we would find that it comprises of four main component parts (Arthur Holmes 1965). The central part is known as the core, which has a solid iron center surrounded by a combined iron, nickel, and sulphur fluid outer core or, which controls the earth’s magnetic field. The next layer is known as the mantle. Most of the world’s heat is created from within this layer of ferro-magnesium silicates. The final layer is the crust, which is formed mainly by rocks. The composition of these rocks is a mixture of chemicals, metals, salt, silicates and oxygen. The crust is that part that forms the landscape and provides the habitat that supports human, animal and plant life. In other words, it is the area where we live and enjoy nature. When we look at all the different and separate continents today, it is difficult to visualize that, around two hundred million years ago, all of these were joined in one block, known as “Pangea.” (Alfred Wegener 1966). In his study, Wegener found that the earths crust was full of cracks, which made it resemble a combination of large jigsaw pieces, called plates. These plates can act in a number of ways. Some will move together, whilst others will separate from each other, leaving a chasm between them, of which the Grand Canyon provides a good example. In both cases, material on the edges of the plates will be affected in some way. Each of the present day continents was situated on one of these plates. Over time, the internal forces of heat from the mantle layer and natural movement, forced these plates to part and evolve into the present world geological structure. If you look at all of the continents, it can be seen how this happened. For example, North and South America fitted snugly against what is now the Asian and African continent (see appendix). The internal forces exert pressure on the earth in three main ways. These pressures can condense or enlarge rock formations. The third manifestation is where two masses will move in a certain direction, for example sideways, but where there is no change in the size or structure of the rocks themselves. This last movement can be most clearly seen in the oceans, where often there are differing depths that have been created in a shelf type of format. A classic example of this can be found with the continental shelf formation, where the change in depth is quite sudden and abrupt, rather than a gradual sloping process. Sun, Wind and Water The landscapes we see around us have many different and varying features, many of which have been fashioned by a number of external forces. Erosion is probably the major force in this respect and it can come from a number of sources, such as wind, water and ice. While these sources can be seen to be unique, in fact in the majority of cases they usually combine within the erosion process that shapes our landscapes. Wind is forceful creator of particular land features, especially in areas where deserts exist, normally close to the equator. In this instance as the warm air rises, forming clouds, the winds blow these away from the equator, both north and south, leaving a dryer condition. As a result, these areas receive significantly reduced rainfall, limiting the amount of vegetation, which would bind the earth’s surface together. The wind also carries particles of plants and rocks with it to create a build up of vegetation and chemical deposits in other areas. The power of the wind, for example in the form of hurricanes, can have a significant effect on the landscape, as well as destroying human habitats. Another major source of erosion is water. Water can change the shape of the landscape and is responsible for the creation of a number of the features we see around us. In many ways, rivers are responsible for much of the shaping of the landscapes. Starting as either as rains high up in the mountains, or from springs, they start as small streams. Then, as Harris and Diver (1999) explain, they “…grew to rivers that cut valleys and canyons. Because the streams flow away from a central high, they radiate like spokes on a wheel....” Over hundreds and thousands of years, the waters will find a route, which is most porous and offers least resistance to the pressure, and carve it’s path down the sides of mountains and hills to flow through the valley’s and eventually come to an end where it forms into lakes or joins with other rivers, with the combined source often joining with the oceans. At its source, high above sea level in the mountains, rivers run at high speeds, carving deep-sided channels as it erodes cuts a path through the rocks it passes over. It carries with it small particles of rocks and other materials. When it reaches the lower lands and valleys, the river slows, leaving the deposits, which over time are smoothed to form its bed and banks. Water in its frozen form, as ice and glaciers, has been responsible for significant changes to the global landscape. Over the past five million years or so, the earth has been subjected to a number of cold periods, which have resulted in the changing shape and paths of glaciers. In these periods, enormous sheets of ice (glaciers) would advance slowly, but relentlessly across the land. Such is the power and force of these glaciers that they were able to literally move mountains, acting like planes to remove all but the hardiest of rock structures. As the earth warmed up again the glaciers would begin to melt and evaporate. As these monsters of ice retreated, and water levels reduced, many of the world’s great lakes were formed with the basins formed by the stronger bedrocks that had not been destroyed by their advance. Over a period of many millenniums, during which many changes took place, the current lake landscapes developed. These can be seen in areas such as Cumbria in the north of England, and the Great lakes of Northern America and Canada. The ocean currents have also affected the formation of our landscapes, particularly at the edges of the continent, where they meet the landmasses. Currents are formed and influenced by the light and rays from the sun. The warmth of the sun is stronger at the equator, with its polar effect being much cooler. Heat will always move from its source towards cooler places, therefore the hot tropical air will move from the equator in the general direction of the poles, causing the winds. As these winds move across the ocean surface, they drag the water in the same direction. The friction that is cause in this event builds the waves that eventually hit the shorelines. The power of these forces erodes the edges of the rocks that form the lands, which has the effect over time of the creation of cliffs, coves and natural harbor. At times, during the millenniums that the currents have been active, huge tracts of former lands have been submerged because of the ocean attacks. Earth’s internal impact. However, perhaps the most dramatic events that change the shape and design of our landscapes are those that emanate from the more aggressive of the earth’s internal activities. Unlike the effects of the sun, wind and water, these events are more noticeable because of their immediate effect upon the face of the globe as we know it. Such events include earthquakes and volcanic activity. Earthquakes are caused by movements of the plates mentioned earlier. In the case of an earthquake however, these movements are immediate, driven by changes in the heated area of the mantle layer of the earth. This either produces a situation where two edges will clash together, forcing the earth’s crusts to either break up or one to rise and move over the top of another. With these events in the past, large mountain ranges would have been formed because of the earthquake. In other instances, the plates will separate dramatically, forming large canyons. Earthquakes can change the shapes of large portions of the earth’s landscapes in a matter of hours or days. Volcano’s can have a similar effect to that of earthquakes. The difference is that their effect tends to be geographically more limited in its effect. However, the change can be just as dramatic. There are thousands of volcanic sites scattered throughout the surface of the earth. Volcanoes are fissures in the earth’s crusts. They can be likened to small holes in the surface, which are lightly covered with a very thin coating of the crust. The earth’s heat source that is contained within the mantle layer of the earth is a volatile and fiery substance, which is constantly seeking a release mechanism. These small fissures provide this release. As the heat source moves it will hit against these fissures and, when the pressures are sufficient, will break through. Such is the power behind the release that it causes the huge eruptions that we see occur. The molten matter, known as lava, then shoots up into the air and, as it cools, will drop back to earth. A volcano can have three effects on the landscape. In the first, the molten lava can cool and solidify to create new land structures, like islands. Secondly, because it has immense power, it can have the effect of destroying an existing island, blasting and scattering the island structure across the ocean floor. Thirdly, it will in any event, change the shape and structure of the landscape immediately surrounding it. The world and landscape within which we live is an ever-changing environment. As has been described here, some of these changes are so gradual that, because of our short life span, we would never notice. Others, such as earthquakes and volcanoes go unnoticed because of their immediate impact. Such are the scale of all these landscape developments though, that we could not fail to notice the difference were we able to transport ourselves a millennium into the future. References Schullery, Paul (2001). America’s National Parks: The Spectacular Forces That Shaped our Treasured Lands. DK Publishing. Harris, D.V and Kiver, E.P, ed. (1999) Geology of U.S. Parklands. John Wiley & Sons Inc. Holmes, Arthur (1965), Principles of Physical Geology, 2nd ed. Nelson. New York. Chapters IV and V. Wegener, Alfred (1966). The Origin of Continents and Oceans. John Biram, translator. Mineola, New York: Dover Publications. APPENDIX Figure 1 Evolution from pangaea Source: http://geology.com/pangea.htm Read More