accretion
1. Process by which an inorganic body grows in size by the addition of new particles to its exterior. It is the mechanism by which primitive planetary bodies are believed to form as a result of the accumulation of minute, cold, homogeneous particles (homogeneous accretion). An alternative hypothesis is that iron-rich cores accumulated first and were later surrounded by silicate material (heterogeneous accretion). Homogeneous accretion yields a planet that initially has the same composition from centre to surface; heterogeneous accretion yields a planet that has a layered structure from the start.

2. The accumulation of sediments from any cause, representing an excess of deposition over erosion.

3. The addition of continental material to a pre-existing continent, usually at its edge. The use of ‘accretion’ in this sense has evolved from theories of nucleation to newer theories of the horizontal addition of allochthonous terranes of initially coherent bodies of continental rock, usually more than 100 km² in area, which can collide, rotate, and fragment as they become sutured to a continent.

ac·cre·tion / əˈkrēshən/ • n. the process of growth or increase, typically by the gradual accumulation of additional layers or matter. ∎  a thing formed or added by such growth or increase.DERIVATIVES: ac·cre·tive / əˈkrētiv/ adj.

ACCRETION

The act of adding portions of soil to the soil already in possession of the owner by gradual deposition through the operation of natural causes.

The growth of the value of a particular item given to a person as a specific bequest under the provisions of a will between the time the will was written and the time of death of the testator—the person who wrote the will.

Accretion of land is of two types: (1) by alluvion, the washing up of sand or soil so as to form firm ground; and (2) by dereliction, as when the sea shrinks below the usual watermark. The terms alluvion and accretion are often used interchangeably, but alluvion refers to the deposit itself while accretion denotes the act. Land uncovered by a gradual subsidence of water is not an accretion; it is a reliction.

accretion XVII. — L. accrētiō, -ōn-, f. accrēt-, pp. stem of accrēscere, f. AC- + crēscere grow. See CRESCENT, -TION.

accretion
1. The process by which an inorganic body grows in size by the addition of new particles to its exterior.

2. The accumulation of sediments from any cause, representing an excess of deposition over erosion.

3. The addition of material to the edge of a continent, thus enlarging it.