Geology Of The Alps
The Alps, a term derived from the French word Alpes, refers to a mountain range system of Europe stretching from Slovenia and Austria in the eastern side to France in the West. Some of the mountains in the Alps include Mont Rosa, Dom, Grand Combin, Weisshorn, and Mont Blanc. The Alps stretch through France, Germany, Liechtenstein, Switzerland, Italy, Austria, and Slovenia. The great mountain system forms a twelve hundred kilometer long arc from Danube River at Vienna to the Gulf of Genoa and occupies an area of about 200,000 sq km. It is also the most densely populated mountain belt in Europe with an estimated twenty million inhabitants.
Economic activities at the great mountain system include hydroelectric power production, tourism, farming, iron ore extraction, and forestry. (Moores & Fairbridge) Geology of the great mountain system Structurally, the great mountain system is divided into the Eastern Alps and the Western Alps. The division is made along the Rhine Valley and Lake Constance and Lake Como. Though their central chain is shorter, the Western Alps are generally higher than the Eastern Alps. The main chain of the Alps, a central line that forms the water divide, follows the watershed starting from the Mediterranean to the Wienerwald.
The great mountain system in Europe is a part of the Alpide belt, a Tertiary Orogenic belt of mountain chains. (Schmid, Fugenshuh & kissling 04) The belt stretches through Europe and Asia up to the Himalayas and was formed during the Alpine orogeny. The Alps are said to have formed as a result of a collision of the European and African tectonic plates leading to the disappearance of the Tethys Ocean. A lot of pressure was put on sediments of the vanished ocean basin and its Mesozoic. The early Cenozoic strata were pushed alongside the static Eurasian landmass.
This enormous stress gave rise to great recumbent folds and pushed northwards and in the process breaking and sliding over one another forming huge thrust faults. The great mountain system forms a northward convex arc around the Po River basin, its southern foreland basin. The Neogene and Quarternary sediments lie dissonant over the south thrust units. There are deposits found at the northeast southward dipping. The thrust front of the Alpine nappes thrusts over the foreland basin deposits from the southward direction. The Jura Mountains, seen as a part of the Alps, rims the Molasse Basin to the northwest.
(Frisch & Kuhlemann 2002) The great mountains system has a complex geology but their structure is relatively similar to other mountain ranges created through continental collision. The Periadriatic Seam, the main suture in the Alps, runs through the Alps from east to west and is the boundary between matter from the Apulian and the former European plates. South of the Periadriatic Seam are the thrust units of the Southern Alps whereas in the north are the Helvetic, Austroalpine and Penninic nappes. The Austroalpine nappes contain material from the Apulian plate and Helvetic from the European plate.
The Penninic nappes contain material from what existed between the European and the Apulian plates. (Moores & Fairbridge) These are the main tectonic subdivisions of the great mount system. Since the thrusts in the three nappes indicated above are directed to the north, their dominant direction of fold asymmetry is to the same direction. The direction of fold asymmetry of the Southern Alps thrusts is dominantly southward. Most of the Eastern Alps outcrops are formed by the Austroalpine nappes rocks but some places such as the Dent Blanche unit eroded away. The Helvetic nappes are found to the north and west of the Western Alps.
Large antiforms referred to as anticlinoria can be found in the central region north of the main suture of the Alps. They are at times displayed in the outcrops as windows. At the level of the Hohe Tauern window, the seam curves north suggesting that the Apulian is extra rigid at this spot. It therefore functions as an indentor. The Lepontin dome formed as a result of an uplift that happened along the fault zone Rhone-Simplon line. (Moores & Fairbridge) The lower crust intrusions are seen to have nothing to do the formation of the Alps since their formation is thought to have taken place during the Hercynian orogeny or shortly after.
During the Tertiary Orogeny, the rocks of the Austroalpine, Helvetic and the Southern Alps did not experience missed out on high grade metamorphism. (Stampfli, Borel & Mosar 2002) It is thought that high grade metamorphic rocks could not have formed at this time due the formation of the Alps. The high grade metamorphic rocks present are therefore thought to have either originated from the lower regions or got to the surface through uplift or formed during the Cretaceous period. (Rudwick 1976)
The great mountain system was formed through folding and thrusting as a result of convergent movements of the Apulian and European plates. This process however started earlier and can be traced back to: 1. Break up of Pangea. 2. The Jurassic period. approximately 180 Ma ago. 3. Eo-Alpine phase. During the Cretaceous period, the first continental collision was experienced. This is regarded by many as the first stage in the formation of the Alps as the Apulian collided with the European plate. 4. The Eocene and the Paleocene.
The Brianconnais microcontinent arrived at the subduction zone beneath the Apulian plate. They were later intruded by migmatites and formed the Penninic nappes. The Austroalpine nappes were thrust over the surface of the European crust. (Schmid, Fugenshuh & kissling 04) The subducting slab fell off resulting to the uplift of the continental crust. An extension of the Alps took place in a west-east direction. Over time, a huge thrust zone evolved and would later become the main suture in the Alps. Due to the erosion of the central zones of the Alps, the tectonic windows and domes were formed.
The Austroalpine and Penninic nappes continued their movement pushing debris and material northward giving rise to the Helvetic nappes. Conclusion The two plates responsible for the formation of the Alps are still converging and the process of mountain formation is still on to date. Measurements conducted in road tunnels suggest that the Alps rise by up to a centimeter each year. Stresses are still found along deep fault lines making the core of the Alps move upwards. The formation of the Bavarian and Po basin still continue with the crust subsiding in these places.
The Alpine landscape is estimated to have formed two million years ago with the ice ages since then remodeling the region a great deal. The flowing glaciers are responsible for moving the top soil into the low hills and scooping out the lakes. Human activity especially in the last one hundred and fifty years has resulted to the change of the flow and levels of all rivers found in the Alps. (Moores & Fairbridge) References Frisch, W. ; Dunkl, I. & Kuhlemann, J. ; (2000): Post-collisional large-scale extension in the Eastern Alps in Tectonophysics pp 301- 353 Moores, Eldridge M.
, Fairbridge, Rhodes W. “Alpine Orogeny. ” Encyclopedia of European and Asian Regional Geology. Chapman &Hall. Rudwick, M. J. S. (1976). The Meaning of Fossils: Episodes in the History of Palaentology. University of Chicago Press. (p. 76-78). Schmid, S. M. ; Fugenshuh, B. ; Kissling, E. & Schuster, R. ; 2004: Tectonic map and overall architecture of the Alpine orogen in Eclogae Geologicae Helvetiae v 97, p 93 Stampfli, G. M. ; Borel, G. D. ; Marchant, R. & Mosar, J. ; 2002: Western Alps geological constraints on western Tethyan reconstructions in: Rosenbaum, G. & Lister, G. S.Sample Essay of EduBirdie.com