8.2 The characteristics and formation of coastal landforms Flashcards
Inter-tidal zone
The zone on the beach between the mean low tide and the mean high tide level.
Backshore zone
The upper part of the beach above the mean high tide level but affected by spring tides and storm waves/
Springtide
Once a fortnight, when the sun and moon are aligned, there is an unusually high tidal range.
Breakpoint bar
A long thin ridge of sediment on the seabed, running parallel to the coastline, at or below the level of the lowest spring tide. They form at the point where waves begin to break.
Barrier beach
Long, sandy beaches, detached from, but parallel to, the coastline.
Barrier island
Long islands running parallel to the coastline. Probably started as barrier beaches, but sand dunes formed on them and vegetation then built them up above high tide level.
Beach cusps
Semi-circular, scalloped depressions cut into the lower edge of the storm beach.
Foreshore
Sometimes called the inter-tidal or surf zone, the zone of the beach between the mean low tide and the mean high tide level.
Tidal range
The difference in height between the low and high tide levels.
Nearshore zone
Sometimes called the breaker zone. The lower part of the beach below the mean low tide level but uncovered by spring tides.
Offshore zone
The zone below the level of the lowest spring tides, never uncovered.
Swash aligned beach
Beaches that are aligned parallel to the crests of the prevailing waves.
Drift aligned beach
Beaches that are aligned at an angle to the crests of the prevailing waves. As a result, LSD takes place.
Cuspate forelands
Low features which extend outwards from the shoreline in a triangular shape. They are formed by the deposition of sand and shingle at the point where two streams of LSD sediment meet.
Simple spit
Spits occur when LSD extends the beach part of the way across an estuary, bay or inlet. Simple spits are sometimes straight but more usually have curved ends.
Compound spit
Compound spits form like a simple spit but they have a narrow base attaching them to the mainland and they widen into a broad, recurved end, consisting of a series of ridges which have grown successively over time.
Offshore bar
Long thin ridges on the seabed, running parallel to the coastline below the level of the lowest spring tide. They are produced when the circular movement of water in the waves starts to touch the seabed.
Bar
A ridge of sand or single that extends right across a bay or inlet.
Tombolo
Outwards beach extension that joins an offshore island. e.g. Chesil beach in Dorset.
Cuspate tombolo
When wave refraction causes LSD to operate in opposite directions either side of an offshore island, the beach extends out to the island, joining it to the mainland at low tide. When two beaches extend to the same island, a cuspate tombolo forms.
Sward zone
A zone of saltmarsh where grasses dominate the ecosystem. It may only be covered by the sea for an hour a day.
Creek
A small channel in a saltmarsh along which the receding seawater drains as the tide goes out.
Storm surge
A rush of water driven onto land by strong winds when the sea surface is raised, either because of expansion caused by heating or because a low-pressure system with its rising air takes a weight off the sea surface, allowing it to rise.
Eustatic
A global change in sea level.
Isostatic
A local change in sea level, usually produced by movements of the land relative to the sea.
Isostatic rebound
During a glacial period the land is pushed down by the weight of the ice sheets. At the end of the glacial period the ice sheets melt and the land slowly rises back to its former level.
Ria
A drowned river valley
Fjord
A drowned glaciated valley
Dalmatian coastline
A drowned coastline with long narrow islands running parallel to the coastline. The islands were the ridges of hills when sea level was lower in the past.
Raised beach
An old beach which is now above the current sea level. Produced by a fall in sea level relative to the land.
Emerged coastal plains
In a part of the world with a wide, shallow continental shelf, a fall in sea level can produce a wide coastal plain, backed by a relict line of cliffs which represent the old coastline.
