Coasts

Wave erosion coasts formed by the force of waves as they strike the land the waves strike the land and pieces of rock are broken off the wave action continues to grind the rock into sand

Wave erosion features Sea cliff – steep structure formed as waves strike the rock Headland – an area of resistant rock projecting out from shore

Sea cave – when waves cut deeply into weak rock Sea arch – when waves cut completely through a headland Sea stack – isolated column of rock once connected to a headland or sea cliff

Wave-cut terrace – a level platform beneath the water surface at the base of a cliff Wave-built terrace – material deposited out from the wave-cut terrace that extends it

Sea Cave

Sea stacks

Depositional coasts Waves erode and deposit sediments along a shoreline to form features

Beach A shoreline feature formed as sand or larger rock fragments are deposited.

Longshore current When waves break, the water continues to rush up the beach (at the same angle as the waves) as swash, but when it stops it runs back down the beach along the greatest slope as backwash. This swash/backwash motion will result in a zigzag movement of the water with a net direction that is the same as the approaching waves and which will produce a longshore current.

Features formed by longshore current Longshore drift – movement of sand by the longshore current Spit – long narrow deposit of sand connected at one end to the shore Tombolo – a ridge of sand that connects an offshore island to the shore Barrier island – formed when sediment is deposited parallel to the shore

Stabilizing the shore – protective structures Groins – a barrier built at a right angle to the beach to trap sand Breakwaters – its purpose is to protect boats from the force of waves Seawalls – a structure built parallel to shore to shield against breaking waves

Groin or jetty

Breakwater

Seawall

Beach Nourishment Addition of large quantities of sand to a beach