Geological structure and the development of coastal landscapes

Three Elements to Geological Structure

• Strata → 🔗 The different layers of rock within an area and how they relate to each other
• Deformation → 🔗 The regress to which rocks have been deformed by tectonic activity
• Faulting → 🔗 The presence of major fractures that have moved rocks from their original positions Results in the following types of coastlines being formed:

Concordant → Rock strata running parallel to the coastline (eg. The Dalmatian Coast in the Adriatic Sea)

• Haff coastlines
• Long sediment ridges topped by sand dunes run parallel to the coast just offshore
• Lagoons (haffs) are created between the ridges and the shoreline

Discordant → Alternating bands of hard and soft rock at right angles to the coastline

• Less resistant rocks are eroded to form bays, whereas more resistant rocks remain as headlands
• Headlands are eroded more than bays because…
• In deep water, crests are parallel
• As water shallows towards the coast, waves slow down & wave height increases ↑
• In bays, wave crests curve to reflect their shape and wave height decreases ↓
• Wave action is concentrated on headlands

Cliff profiles

Influenced by…

• The resistance of the rock to erosion

• The dip of the rock strata

  

• Faulting → Major fractures in rocks produced by tectonic forces and involving the displacement of rocks on either side of the fault line

• Natural cracks - jointing and fissures → joints occur in most rocks, dividing the rock strata up into blocks with a regular Fissures often only occur a few cm/mm long ↳ The location of micro features within cells, such as caves, are often controlled by the location of faults and/or strata which have a particular high density of joints & fissures