THE WORK OF THE OCEAX. 363 



from straightness. Winds which simply reverse the direction of the 

 littoral cmTent retard its construction, but may not otherwise affect it; 

 but if a strong cuiTent be made to flow past the end of a spit, it may 

 cut away its extremity and rebuild the materials into a smaller spit, 

 joining the main one at an angle. This gives rise to a Jwok (Fig. 315). 

 Successive storms may develop successive hooks along the side of a 

 growing spit. The end of a hook may be so extended as to join the 

 mainland, when it becomes a loop. 



Wave-built terraces. — Under the influence of off-shore ciu'rents, 

 littoral currents may be drawn from the coast-line. If such a current 

 contmues as a well-defined surface-cm-rent, it builds a spit, but if it 

 spreads, it tends to build a terrace. The accumulation then is not at 

 the end of a beach, as in the case of a spit, but on its side, and the 

 result of the deposition is to carry the beach seaward. The undertow 

 abets the process. The widened beach is a wave-built terrace. The 

 wave-built terrace often borders the wave-cut terrace along its seaward 

 margin ^Figs. 303 and 31S\ "\Mth the help of waves, the surface of the 

 terrace may be built up into land by the expansion of the crest of the 

 beach. Terrace-cuttmg and terrace-building are both involved in the 

 development of the continental shelves. 



Beach ridges, spits, bars, etc., like sea-cliffs and wave-cut terraces, 

 are often preserved after the relative level of sea and land has changed. 

 If the shore has risen, relatively or absolutely, these featm'es are relied 

 on as evidences of the change. If shore features be submerged instead 

 of elevated, they fm'nish less accessible, though not less real, evidence 

 of the change of level. vSimilar features about lakes have a like signifi- 

 cance, but in this case it is often demonstrable that it is the water rather 

 than the land which has changed its level. 



Effect of Slw re-deposition on Coastal Configuration. 



The tendency of shore-deposition is to cut oft' bays and to straighten 

 and simplify the shore-lines. This is abmidantly illustrated along the 

 Atlantic and Guff coasts of the United States (see Fig. 319 and PI. XXII). 

 It is to be noted, however, that in the simplification of the shore-line 

 tln^ough deposition, the initial stages often result in great irregularity 

 (Fig. 320 and PI. XXIII). In some cases, the irregularities are not tern- 



