sea floor spreading
The oceanic ridge is the sea floor elevated which is situated along well developed divergent plate boundaries. The interconnected oceanic ridge system, is the longest feature on the earths surface, representing twenty percent. The sea floor spreading is a term applied to the mechanism long the oceanic ridge system to create sea floor. Mostly the spread is about five centimetres per year; similar to the rate our fingernails grow (Tarbuck and Lutgens, 1993).
As Alfred Wegener proposed, when divergent plate boundaries develop within a continent, the land mass may split into two or more segments. This continental splitting is considered to start with the formation of an elongated depression called a continental rift. A current example of this is the East African rift, which may develop into a fully fledged spreading centre and split the African continent into two. A different example is, Mount Kilimanjaro which has extensive volcanic activity that accompanies continental rifting. This could lead to the rift valley lengthening, deepening and extending to the plate margin to split the plate in two. This will lead to a narrow sea with an outlet to the ocean, similar to how the red sea was formed (Chernicoff and Venatakrishnan, 1995).
Although new land is being constantly formed through oceanic ridges, we are also loosing land consistently through destructive plate margins. This occurs along convergent boundaries, also called subduction zones. In this case, at the convergent plate margins, two plates move towards each other leading to one plate sliding beneath the other. This is what forms a deep ocean trench. The Andes mountains in South America, are partly formed by volcanos, in association with oceanic-continental convergence called continental volcanic arcs. Oceanic-oceanic convergence, called volcanic island arcs, lead to an arc shaped chain of small volcanic islands; the Tongan islands are an example of this. You can also have continental-continental convergence, this is where two continental plates run into each other. An example of this is the formation of the Himalayan Mountains, when the Indian subcontinent rammed into Asia. Finally, you can have two plates slide horizontally past each other without the destruction or formation of landforms, this is called a transform fault boundary and can lead to breaks in the earths crust known as fracture zones (Tarbuck and Lutgens, 1993).
As Alfred Wegener proposed, when divergent plate boundaries develop within a continent, the land mass may split into two or more segments. This continental splitting is considered to start with the formation of an elongated depression called a continental rift. A current example of this is the East African rift, which may develop into a fully fledged spreading centre and split the African continent into two. A different example is, Mount Kilimanjaro which has extensive volcanic activity that accompanies continental rifting. This could lead to the rift valley lengthening, deepening and extending to the plate margin to split the plate in two. This will lead to a narrow sea with an outlet to the ocean, similar to how the red sea was formed (Chernicoff and Venatakrishnan, 1995).
Although new land is being constantly formed through oceanic ridges, we are also loosing land consistently through destructive plate margins. This occurs along convergent boundaries, also called subduction zones. In this case, at the convergent plate margins, two plates move towards each other leading to one plate sliding beneath the other. This is what forms a deep ocean trench. The Andes mountains in South America, are partly formed by volcanos, in association with oceanic-continental convergence called continental volcanic arcs. Oceanic-oceanic convergence, called volcanic island arcs, lead to an arc shaped chain of small volcanic islands; the Tongan islands are an example of this. You can also have continental-continental convergence, this is where two continental plates run into each other. An example of this is the formation of the Himalayan Mountains, when the Indian subcontinent rammed into Asia. Finally, you can have two plates slide horizontally past each other without the destruction or formation of landforms, this is called a transform fault boundary and can lead to breaks in the earths crust known as fracture zones (Tarbuck and Lutgens, 1993).