Page 545 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 16 Oceans, Coastal Systems, and Wind Processes 509
Barrier spit
Tidal inlet
Bay barrier
(a) The Limantour barrier spit nearly blocks the entrance to Drakes Estero, along Point Reyes, California.
(b) A barrier spit forms Morro Bay, California, with the sound opening to the sea near 178-m Morrow Rock, a volcanic plug.
(d) A sand beach formed by wave action at Blooming Point spit on the north shore of Prince Edward Island.
(e) A shell beach deposited by the ocean.
Beach
Tombolo
Wave-cut platform Wave-built terrace
Barrier spit
Tidal inlet
Lagoon
Bay barrier
(c) A tombolo at Point Sur along the central California coast, where sediment deposits connect the shore with an island.
▲Figure 16.14 Depositional coastal landforms: barrier spits, lagoons, tombolos, and beaches. [(a)–(c) and (e) Bobbé Christopherson. (d) Mary-Louise Byrne.]
while in active transit along the shore. Beaches occur along seacoasts, lakeshores, and rivers (Figure 16.14d). Not all the beaches of the world are composed of sand, for they can be made up of shingles (beach gravel) and shells, among other materials (Figure 16.14e). Gravels re- flect the contribution of stream sediments into coastal areas; shells reflect the contribution of materials from oceanic sources. Beaches vary in type and permanence, especially along coastlines dominated by wave action.
On average, the beach zone spans the area from about 5 m above high tide to 10 m below low tide (see
Figure 16.5). However, the size and location of the beach zone varies greatly along individual shorelines. World- wide, quartz (SiO2) dominates beach sands because it resists weathering and therefore remains after other min- erals are removed. In volcanic areas, beaches are derived from wave-processed lava. Hawai‘i and Iceland, for ex- ample, feature some black-sand beaches.
Many beaches, such as those in southern France and western Italy, lack sand and are composed of peb- bles and cobbles—a type of shingle beach. Some shores have no beaches at all, but are lined with boulders and
Morro Rock
Morro Bay