1 On a gently sloping coastline, a submarine accumulation of marine sediment, which may be exposed at low tide. Most bars form where steep, destructive waves break; such bars can be called break-point bars, with crests generally running parallel to the coast. Bay bars extend across an estuary or a bay: ‘it seems likely that [Chesil Beach, UK] began as a bay bar…when the sea level was lower’ (I. West2007). Some bay bars entirely enclose the inlet, and a lagoon may then form on the landward side; see Roberts and Slater (2007) Holocene 17. Offshore bars, located further out to sea, are thought to result from the breaking of larger waves, which erode the sea bed and throw up material ahead of them to form ridges (Hoefel and Elgar (2003) Science 29).
2 In a glacial trough, such as the Nant Ffrancon of North Wales, a transverse rocky barrier (Embleton (1961) Transactions and Papers, IBG, 29).
3 Within a river, a deposit of alluvium, dropped where velocity and turbulence are low, and which may form temporary islands. Alternating bars develop as patches of alluvium, often regularly spaced, along opposite sides of a straight channel. Braid bars, roughly diamond shaped, are generally aligned along the channel course; Best et al. (2003) J. Sed. Res. 73, 4 provide ‘a unique [authors’ italics] insight into the process-product relationship of braid-bar'. Point bars form on the inner curves of a meandering river where discharge is low; see Pyrce and Ashmore (2005) Sedimentol. 52, 4.