Influence of Geological Structure (Edexcel A Level Geography)

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Bridgette Barrett

Written by: Bridgette Barrett

Reviewed by: Jenna Quinn

Discordant & Concordant Coast Formation

Discordant coastlines

  • A discordant coastline is one where the rock structures meet the coast at an angle - run perpendicular to oncoming waves

  • Alternating rock types lead to the formation of headlands and bays

  • Discordant coasts are also known as Atlantic coasts

Concordant coastlines

  • Concordant coastlines are where the rock structures run parallel to the coast

  • Dalmatian and Haff coastlines are examples of concordant coastlines

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Discordant and concordant coastline

Influence of Geology on Coastal Morphology

  • The shape and form of the coastline is known as coastal morphology

    • This is influenced by the rock type (geology) and structure

Concordant coastlines - examples

Dorset, UK

  • An example of a concordant coastline can be found in the area around Lulworth Cove in Dorset

  • More resistant Portland Limestone runs parallel to the sea with less resistant Purbeck Limestone and Wealden Clay behind it

    • The formation of coves has occurred where the water has broken through at weaker points in the Portland Limestone

coast-morphology-1-1
Concordant coastline in South Dorset

Dalmatian coastline

  • The Dalmatian coast in Croatia is another example of a concordant coastline

  • Formed as a result of tectonic forces and sea level rise 

  • Tectonic activity forms anticlines and syncline which run parallel to the sea 

  • Sea level rise after the Devensian Glacial then flooded the synclines leaving the anticlines standing above the water

  • The result is a series of islands which run parallel to the coast

Dalmatian Coastline
Example of a Dalmatian coastline

Haff coastline

  • Located along the southern Baltic coastline

  • During the Devensian Glacial large amounts of sand and gravel were deposited offshore

  • After the glacial period had ended the material was then deposited nearer to the land by constructive waves

  • This formed bars across bays and river mouths trapping the water behind to form a lagoon (Haff)

  • These are a feature of low-energy coastlines

Haff Coastline
Haff coastline on the Baltic coast

Discordant coastlines - examples

Dorset, UK

  • To the east of Lulworth Cove in Dorset, the coastline runs north to south and so the rocks meet the coast at an angle creating a discordant coastline

  • This leads to the formation of headlands and bays

coast-morphology-1
Headland and bay formation
  • The area is also affected by wave refraction

    • Wave refraction changes the amount of energy reaching the shore on a small local scale

    • Wave energy concentrates at the headland and increases the rate of erosion

wave-refraction
Wave refraction around headlands

Influence of Geological Structure

  • The geological structure is the way that rocks are folded or tilted - this is known as its lithology

  • Lithology can refer to any of the following characteristics:

    • Strata - layers of rock

    • Bedding planes - horizontal cracks created by pauses in rock formation

    • Joints - vertical cracks caused by tectonic movement or contraction

    • Folds - the result of pressure during tectonic movement causing the rock strata to fold

    • Faults - the result of stress or pressure causing it to fracture

    • Dip - the angle of the rock strata

Cliff profiles

  • Cliff profiles are the angle and height of the cliff face

  • A profile also includes any features such as wave cut notches

  • Different lithology creates different cliff profiles

Cliff Profile - Geological Structure
Impacts of lithology of cliff profiles

Examiner Tips and Tricks

You may be asked in the exam to explain the formation of a particular cliff profile. It is essential that you consider the lithology of the cliff face but also the other processes which act upon a cliff including:

  • Hydraulic action and abrasion 

  • Subaerial processes 

  • Wave type

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Bridgette Barrett

Author: Bridgette Barrett

Expertise: Geography Lead

After graduating with a degree in Geography, Bridgette completed a PGCE over 25 years ago. She later gained an MA Learning, Technology and Education from the University of Nottingham focussing on online learning. At a time when the study of geography has never been more important, Bridgette is passionate about creating content which supports students in achieving their potential in geography and builds their confidence.

Jenna Quinn

Author: Jenna Quinn

Expertise: Head of New Subjects

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.