Slab (geology)
Encyclopedia
In geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

, a slab is the portion of a tectonic plate that is being subducted
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...

.

Slabs constitute an important part of the global plate tectonic system. They drive plate tectonics both by pulling along the lithosphere
Lithosphere
The lithosphere is the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.- Earth's lithosphere :...

 to which they are attached in a processes known as slab pull
Slab pull
The Slab pull force is a tectonic plate force due to subduction. Plate motion is partly driven by the weight of cold, dense plates sinking into the mantle at trenches. This force and the slab suction force account for most of the overall force acting on plate tectonics, and the ridge push force...

 and by inciting currents in the mantle (slab suction
Slab suction
Slab suction forces are one of the major plate tectonic driving forces. Slab suction occurs when a subducting slab drives flow in the nearby mantle. This flow then exerts shear tractions on nearby plates. This driving force is important when the slabs are not strongly attached to the rest of...

). They cause volcanism
Volcanism
Volcanism is the phenomenon connected with volcanoes and volcanic activity. It includes all phenomena resulting from and causing magma within the crust or mantle of a planet to rise through the crust and form volcanic rocks on the surface....

 due to flux melting
Flux melting
In igneous petrology flux melting occurs when water and other volatile components are added to a hot solid rock. The ultramafic rock of the upper mantle can be melted by the addition of volatiles from below. The source of the water and volatiles is the subducting slab of oceanic crust which...

 of the mantle wedge
Mantle wedge
A mantle wedge is a zone of mantle, triangular in cross–section, that lies between subducting and overriding tectonic plates. Flow inside the wedge is aligned with plate motions. Flux melting of material within wedge due to the release of volatiles from the underlying subducting slab results in...

, and they affect the flow and thermal evolution of the Earth's mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....

. Their motion can cause dynamic uplift and subsidence
Dynamic topography
The term dynamic topography is used in geodynamics and oceanography to refer to elevation differences caused by the flow within the Earth's mantle and the ocean water, respectively.-Geodynamics:...

 of the Earth's surface, forming shallow seaways and potentially rearranging drainage patterns.

Slabs have been imaged down to the seismic discontinuities between the upper and lower mantle and to the core–mantle boundary
Core–mantle boundary
The core–mantle boundary lies between the Earth's silicate mantle and its liquid iron-nickel outer core. This boundary is located at approximately 2900 km of depth beneath the Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth...

. Slab subduction is the mechanism by which lithospheric material is mixed back into the Earth's mantle.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK