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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.
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.
Diagram of accretion and erosion of sediments in a coastal system. Black arrows indicate accretion, and white arrows indicate erosion. Sedimentary budgets are a coastal management tool used to analyze and describe the different sediment inputs (sources) and outputs (sinks) on the coasts, which is used to predict morphological change in any particular coastline over time.
The first is by frontal accretion, in which sediments are scraped off the downgoing plate and emplaced at the front of the accretionary prism. [2] As the accretionary wedge grows, older sediments further from the trench become increasingly lithified , and faults and other structural features are steepened by rotation towards the trench. [ 27 ]
For example, in the central Mariana Trough, current spreading rates are 2–3 times greater on the western flank, [8] whereas at the southern end of the Mariana Trough the position of the spreading center adjacent to the volcanic front suggests that overall crustal accretion has been nearly entirely asymmetric there. [9]
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
Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System. Initially, Earth was molten due to extreme volcanism and frequent collisions with other bodies.