Where does accretion collide?

In Roman law, Justinian's Institutes (533) treated alluvio, the soil that a river adds little by little to a bank, as land that passes to the owner of the adjoining field. Blackstone's Commentaries on the Laws of England (1766) carried the doctrine into English common law, where accretion is the gradual and imperceptible addition of land where water meets shore, and it gives that new ground to the abutting owner. The referent is a change in the legal ownership of real property, traced along a shifting boundary, and it has nothing to do with gas drawn onto a star, crust joined to a continent, or value added to a bond.[1][2]

Unit

A parcel of newly added land, by area along a shifting water boundary

Recovery means

Not applicable

Measured by

Established by survey of the boundary and by legal tests of gradual, imperceptible deposit

Hoyle and Lyttleton's 1939 The evolution of the stars introduced the idea that a star moving through interstellar gas draws in surrounding matter by its gravity, a process later set out for the simplest case by Bondi's 1952 On spherically symmetrical accretion. Shakura and Sunyaev's 1973 work on black holes in binary systems described how gas with spin settles into a flat, rotating accretion disk and spirals inward while radiating. The referent is matter accumulating onto a star, black hole, or forming body under gravity, scaled as a rate of mass gain, and it is unrelated to soil added to a riverbank, crust added to a continent, or value added to a bond.[3][4][5]

Unit

Matter gained by a body, scaled as an accretion rate in mass per unit time

Recovery means

Not applicable

Measured by

Inferred from the luminosity of the infalling gas and modelled from the disk structure and mass-flow rate

Coney, Jones, and Monger's 1980 Cordilleran suspect terranes framed how a continent grows by adding terranes, fault-bounded blocks of crust with their own distinct histories that are carried in and welded onto a margin. In this tectonic meaning accretion is the lasting attachment of such crustal blocks to a continent, often at a subduction zone where oceanic material is scraped off and stacked against the edge. The referent is the growth of continental crust, described by the age and boundaries of the added blocks, and it differs from soil that a river adds to a bank, matter pulled onto a star, or value added to a bond.[6]

Unit

A crustal block added to a continent, by its age, area, and bounding faults

Recovery means

Not applicable

Measured by

Mapped by structural geology and dated by the rocks and fossils of the added terrane