Coasts Flashcards
(100 cards)
Low-energy vs high-energy coast
Low:
•constructive waves
•longshore drift, deposition
•spit, tombolo, beach bar, salt marsh, beach
•east coast
•Anglian coast
High:
•destructive
•erosion - hydraulic action, abrasion, attrition, solution
•headland, bay, cave, arch, stack, stump, wave cut platform + notch
•west coast
•Atlantic coast
The coastal system
Inputs -> processes -> outputs
Define dynamic equilibrium
Moving balance
If we alter the coast it will shift back to maintain its system
Processes that affect contrasting coastlines
•geology (rock type):
-Igneous - hardest
-Metamorphic - changed - heat - pressure - mostly very hard
-Sedimentary - young are very weak, old are quite hard
•level of energy:
-wave caused by wind
-open ocean, long fetch - lots of energy
-enclosed seas, short fetch - lower energy
•balance between erosion + deposition
•changes in sea level - emergence & submergence:
-emergence = growing/getting bigger
-submergence = sinking
-10000 years ago - ice age, covered half UK, crustal loading - ice pushed Scotland down but dynamic equilibrium means south England rose (emergent) so Scotland is now emerging + England is now submerging = isostatic rebound
Littoral zone
Coast -> backshore -> foreshore -> nearshore -> offshore
Explain spring tide
An extra high tide due to the alignment of the earth, moon and sun creating an extra gravitational pull on the tidal bulge
Define sediment cell
Length of coastline + nearshore area within which the movement of coarse sediment is largely self-contained
Explain the three different coastlines
•cliffed coast: short littoral zone -> cliff to sea -> lack of beach
•sandy coastline: full range of littoral zone - coast, backshore, foreshore, nearshore, offshore
•estuarine coastline: mouth of rivers, mud flats, salt marsh -> long transition from land to sea -> lots of deposition
Field sketch
•outline drawing highlighting the important geographical points
•annotated
•key terms
•not coloured
•label features + processes
•doesn’t include items of general interest
Discordant vs concordant coastlines
Discordant: hydraulic action, abrasion, attrition, solution erode coast. Soft rock e.g. young sedimentary erode quickest = bay. Harder rock e.g. old sedimentary erode slower = headland. Coastline perpendicular to sea
Concordant: hard rock -> igneous, metamorphic or old sedimentary. Erode at same rate so fairly straight coast. Parts may erode with soft rock behind + form bays. Coastline parallel to sea. If water gets behind hard rock could lead to strips of land with ocean behind.
Explain wave refraction
Waves reorientated as they approach coast. Frictional drag exerted by sea floor turns wave to break parallel to shore
Explain tidal currents
Incoming + outgoing tides produce currents in opposite directions but one direction is stronger so causes one-way transport of sediment
Explain weathering
Breakdown of rock by chemical, mechanical or biological agents - doesn’t involve movement
•chemical - carbonation, hydrolysis, oxidation
•mechanical - freeze-thaw, salt crystallisation
•biological - plant roots, rock boring
Mandala grid
Geological factors affecting the shape of the coastline
•horizontal dip - vertical profile with notches reflecting strata that are more easily eroded
•Seaward dip, high angle - Sloping, low angle profile with one rock layer facing the sea; vulnerable to rock slides down the dip slope
•Seaward dip, low angle - Profile may exceed 90° producing areas of overhanging rock; very vulnerable to rock falls
•Landward dip - Steep profiles of 70-80° producing a very stable cliff with reduced rock falls
Define strata
Layers of rock
Define bedding planes (horizontal cracks)
These are natural breaks in the strata, caused by gaps in time during periods of rock formation
Define joints (vertical cracks)
These are fractures, caused either by contraction as sediments dry out, or by earth movements during uplift
Define folds
Formed by pressure during tectonic activity, which makes rocks buckle and crumble (e.g. the Lulworth Crumple)
Define faults
Formed when the stress or pressure to which a rock is subjected, exceeds its internal strength (causing it to fracture). The faults then slip or move along fault planes
Define dip
This refers to the angle at which rock strata lie (horizontally, vertically, dipping towards the sea, or dipping inland)
Define relief
Height and slope of land
Define morphology
Shape
Define wave period
Time taken for two crests to pass a given point