Discuss the Contention that Landscape Development is Largely Driven by Periods of Tectonic Activity.
Discuss the Contention that Landscape Development is Largely Driven by Periods of Tectonic Activity.
Landscapes are constantly changing. Whether it is a local landscape, a country or the entire planet, landscapes are changing. The current position of the earths land masses have changed over millions upon millions of years from one super-continent 160 million years ago, to the almost fully dispersed positions they are in today (Burbank and Anderson 2001). This move from a super-continent to the fully dispersed state is thought to be a cycle, which once it is fully dispersed the continents will move back together to reform a super-continent once more (Burbank and Anderson 2001). The theory of continental drift has become more and more widely accepted for two reasons, firstly, the fit of continental shelves on both sides of the Atlantic and remarkable exact depths of 900m, and secondly, the symmetry of the mid-Atlantic Ridge (Pitty 1971).
This essay intends to recognise the importance of tectonic activity in the development of landscapes and discuss the theories put forward by geomorphologists to try to explain landform development. This essay will also attempt discuss to what extent these geomorphologists see tectonic activity as a primary role in landscape development. Tectonic activity also produces its own landforms. Not only is it responsible for continental positioning but also features such as volcanoes and fault lines. One major feature of tectonic activity is deep ocean trenches. When two oceanic plates collide, it results in the creation of a volcanic island arc and the formation of an ocean trench. The Philippine Island Arc zone and the Tongan Island Arc zone are examples of these. The Tongan ocean trench represents the subduction of the Pacific plate under the Fiji plate. The subducted plate will be slightly denser and so will more readily sink into the mantle. This plate will be forced under at, in the Fiji – Pacific case around 20 degrees. When it reaches a depth of around 600 kilometres where it is completely absorbed into the mantle. Rising plumes of magma erupt at the surface on the ocean floor, forming volcanoes and eventually volcanic island arcs. These island arcs are common around the west side of the Pacific Ocean. The non-subducted plate may become buckled to produce an outer arc ridge, of which Barbados is an example today (www.ucmp.berkeley.edu). Another major tectonic feature is a mountain range. When two continental plates collide, here no subduction occurs, but sheets of oceanic sediments are folded upward to form Fold Mountains. The continental plate becomes folded and buckled however volcanic activity is rare, even though large batholiths will be expected to form underneath the Fold Mountains. An example of this type of plate margin is Indian – Eurasian plate boundary. Here the continental crust of India has collided with Asia and formed the Himalayas fold mountain range. This is an example of how tectonics control the major relief features on the earth today, with the Himalayas being the tallest mountain range and uplift is still occurring today. (www.ucmp.berkeley.edu). This theory explains why marine fossils, millions of years old have been found in mountain ranges and also at extremely high altitudes.
