Mid+Ocean+Ridges

=Mid Ocean Ridges !=

The driving force behind the process of plate tectonics is heat generated deep inside the earth’s core by radioactive decay. This heat reaches the surface primarily along the Mid-Ocean Ridge. One of the earth’s most dramatic topographical features, the Mid-Ocean Ridge is a continuous range of undersea mountains more than 12,000 feet high and 1,200 miles wide winding through 40,000 miles of the world’s oceans. It is here, at Mid-Ocean Ridges, that new sea-floor crust is produced and much of the earth’s internal heat is released. At Mid-Ocean Ridges, two plates are pulling apart from each other as hot magma (liquid rock) emerges from the mantle and oozes forth as lava to fill the crack continuously created by plate separation. The lava cools and attaches itself to the trailing edge of each plate, forming new ocean floor crust in a process commonly known as sea-floor spreading. All plates have a so-called ‘leading edge’ and ‘trailing edge’. The leading edge is simply the front of the plate, that edge which ‘leads’ the plate in the direction that it is moving. The trailing edge is the back end of the plate. At Mid-Ocean Ridges new crust is added to the trailing edge of each of the two separating, or diverging, plates. Hence, the further sea-floor crust is from the mid-ocean ridge, the older it is. All plates have a so-called ‘leading edge’ and ‘trailing edge’. The leading edge is simply the front of the plate, that edge which ‘leads’ the plate in the direction that it is moving. The trailing edge is the back end of the plate. At Mid-Ocean Ridges new crust is added to the trailing edge of each of the two separating, or diverging, plates. Hence, the further sea-floor crust is from the mid-ocean ridge, the older it is. http://www.platetectonics.com/book/page_8.aspThis uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.  The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean, making the mid-oceanic ridge system the longest mountain range in the world, with a total length of about 60,000 km. There are two processes, ridge-push and slab-pull, thought to be responsible for the spreading seen at mid-ocean ridges, and there is some uncertainty as to which is dominant. Ridge-push occurs when the weight of the ridge pushes the rest of the tectonic plate away from the ridge, often towards a subduction zone. At the subduction zone, "slab-pull" comes into effect. This is simply the weight of the tectonic plate being subducted (pulled) below the overlying plate dragging the rest of the plate along behind it. The other process proposed to contribute to the formation of new oceanic crust at mid-ocean ridges is the "mantle conveyor" (see image). However, there have been some studies which have shown that the upper mantle (asthenosphere) is too plastic (flexible) to generate enough friction to pull the tectonic plate along.