What type of plate boundary destroys old crust

This melting leads to heat being transferred upwards and uplifting the crust, eventually developing into a volcano. Subduction zones are the reason why oceanic crust older than million years old cannot be found. Old, dense crust tends to be subducted back into the earth.

An example of a subduction zone formed from a convergent boundary is the Chile-Peru trench. The last type of plate boundary is the transform boundary, which is where two plates slide past one another. Unlike the other two types of plate boundaries in which new seafloor is created at divergent boundaries and where old seafloor is subducted at convergent boundaries, transform plate boundaries neither create nor destroy the seafloor.

The rubbing caused by the sliding is what causes earthquakes along the transform faults; one example would be the San Andreas fault. Two main tectonic structures are spreading centers and subduction zones. Spreading centers occur at the boundary between two plates that are moving apart, called divergent plate boundaries.

Here the plate motion opens a gap between the plates and magma from the mantle rises up through it. When the magma reaches water at the ocean floor most spreading centers are in the ocean , it cools and hardens, and becomes new oceanic crust. As the plates continue to move apart, more and more new basaltic crust is created.

The most famous spreading center is the Mid-Atlantic Ridge , but there are many others. California has a small spreading center located in the Brawley Seismic Zone of Imperial County, the northern-most spreading center of the East Pacific Rise. If new crust is created, then it must be destroyed some where, otherwise the Earth would grow, which it cannot. Crust is consumed in subduction zones. When two plate move together, one of them must slide under the other one.

This is called subduction. When an oceanic plate and a continental plate meet, the denser oceanic plate subducts under the less dense continental plate. The subducting plate slips down into the mantle where it is heated, melts and is recycled.

Thus spreading centers and subduction zones act like a conveyor belt, manufacturing crust at one end and consuming it at the other. When two plates come together, it is known as a convergent boundary.

The impact of the colliding plates can cause the edges of one or both plates to buckle up into a mountain ranges or one of the plates may bend down into a deep seafloor trench. A chain of volcanoes often forms parallel to convergent plate boundaries and powerful earthquakes are common along these boundaries.

The Pacific Ring of Fire is an example of a convergent plate boundary. At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents.

Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed.