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In geology, accretion is a process by which material is added to a tectonic plate at a subduction zone, frequently on the edge of existing continental landmasses. The added material may be sediment, volcanic arcs , seamounts , oceanic crust or other igneous features.
The jets are byproducts of accretion: they carry away excessive angular momentum. The classical T Tauri stage lasts about 10 million years [8] (there are only a few examples of so-called Peter Pan disks, where the accretion continues to persist for much longer periods, sometimes lasting for more than 40 million years [17]).
A classic example is the Coast Range ophiolite of California, which is one of the most extensive ophiolite terranes in North America. This oceanic crust likely formed during the middle Jurassic Period, roughly 170 million years ago, in an extensional regime within either a back-arc or a forearc basin.
Accretion is the process of coastal sediment returning to the visible portion of a beach or foreshore after a submersion event. [1] A sustainable beach or foreshore often goes through a cycle of submersion during rough weather and later accretion during calmer periods.
Accretion (coastal management), the process where coastal sediments return to the visible portion of the beach following storm erosion; Accretion (geology), the increase in size of a tectonic plate by addition of material along a convergent boundary; Accretionary wedge
In Barcelona, for example, the accretion of the coast was a natural process until the late Middle Ages, when harbor-building increased the rate of accretion. The port of Ephesus , one of the great cities of the Ionian Greeks in Asia Minor , was filled with sediment due to accretion from a nearby river; it is now 5 kilometers (3.1 mi) from the sea.
Accretion disk jets: Why do the disks surrounding certain objects, such as the nuclei of active galaxies, emit jets along their polar axes? These jets are invoked by astronomers to do everything from getting rid of angular momentum in a forming star to reionizing the universe (in active galactic nuclei), but their origin is still not well understood.
The captured material forms a gaseous accretion disc and spirals inwards to ultimately fall onto the neutron star as in the binary system Cen X-3. For still other types of X-ray pulsars, the companion star is a Be star that rotates very rapidly and apparently sheds a disk of gas around its equator. The orbits of the neutron star with these ...