Formation of the Himalayans and the Tibetan Plateau due to Continent-Continent Convergence Thus, the fragments of oceanic crust are plastered against the plates causing welding of two plates known as suture zone. Suture zone: The subduction of the continental crust is not possible beyond 40 km because of the normal buoyancy of the continental crust. Examples: The Himalayas, Alps, Urals, Appalachians and the Atlas Mountains.As two massive continents weld, a single large continental mass joined by a mountain range is produced.The mountain belt erodes, and this is followed by isostatic adjustment. With the building up of resistance, convergence comes to an end.Huge slivers of rock, many kilometres wide are thrust on top of one another, forming a towering mountain range.As the continental plates converge, the ocean basic or a sedimentary basin (geoclinal or geosynclinal sediments found along the continental margins) is squeezed between the two converging plates.The two plates converge, buckle up ( suture zone), fold, and fault. In most cases, neither plate subducts or even if one of the plates subducts, the subduction zone will not go deeper than 40 – 50 km.In Continent-Continent Convergence, at continent-continent convergent margins, due to lower density, both of the continental crustal plates are too light (buoyant) to be carried downward (subduct) into a trench.In ocean-ocean convergence and continent-ocean convergence, at least one of the plates is denser and hence the subduction zone is quite deep (few hundred kilometres).Understanding Continent-Continent Convergence is important to understand the Formation of the Himalayas, the Alps, the Urals and the Atlas Mountains. Collision of continent and arc, or continent-arc convergence.Ĭontinent-Continent Convergence or The Himalayan Convergence.Collision of continental plates or continent-continent convergence (formation of fold mountains).Collision of continental and oceanic plates or ocean-continent convergence (formation of continental arc s and fold mountains).Collision of oceanic plates or ocean-ocean convergence (formation of volcanic island arc s).In convergence there are subtypes namely: When one of the plates is an oceanic plate, it gets embedded in the softer asthenosphere of the continental plate, and as a result, trenches are formed at the zone of subduction.Along a convergent boundary two lithospheric plates collide against each other.the Himalayas formed in this manner beginning about 50 million years ago.Continent-Arc Convergence or New Guinea Convergence The lighter continental crust piles, folds and buckles. Continental-Continental convergence zones usually arise from an oceanic-continental convergence that has consumed all the oceanic crust.Examples include, the Aleutians, the Philippines and the Marianas. Subducting oceanic crust again forms a volcanic arc of islands. The magma rises and as pressure on it decreases, becomes more liquid. ![]() Below 50 km, the descending plate melts partially and release volatiles such as water. In an oceanic-oceanic plate boundary, the sediments of the subducting ocean crust are scraped off and accumulate on the end of the overriding plate. The Andes and cascade ranges are examples of these volcanic mountain ranges. ![]() Magma melts some of the continental crust as it rises to form a volcanic arc on the continent. This collection of rocks is recognizably different from the rocks created by the descending and melting oceanic crust. As the denser oceanic crust is trust under the lighter continental crust, sediments and seamounts are scraped off. Very complex assemblages of rock can be created at oceanic-continental convergence zones. Given the two type of Earth crust (ocean and continental), there are three possibilities for convergent boundaries. The San Andreas fault is a transform fault. They connect divergent and convergent boundaries to form a continuous boundary around a plate. Plates can also move past each other without creation or destruction of crust. ![]() Rifts areas active today include the Afar valley of East Africa and the Atlantic mid-ocean ridge. A new ocean basin is created with the mid-ocean ridges marking the active plate boundary. On land a rift valley will form, but eventually the rift will connect to the ocean and be flooded. Magma from the mantle is injected in thin sheets as the plates separate. Here the Earth's crust is being torn asunder by convection currents in the mantle. Plate Boundary Diagrams This diagram from the USGS shows a complete system of plate boundaries: There are three types of tectonic plate boundaries:
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |