Coasts

Coastal systems and landscapes

Eustatic sea-level change

A global change in sea level caused by variations in the volume of water in the oceans, typically due to melting land ice or thermal expansion.

Isostatic sea-level change

A localised change in land level relative to the sea, caused by uplift or subsidence of the Earth's crust (e.g., post-glacial rebound).

Submergent coastal landforms

Landforms created by rising sea levels, including rias, fjords, and Dalmatian coasts.

Emergent coastal landforms

Landforms exposed by falling sea levels or land uplift, such as raised beaches and marine terraces.

Hard engineering (coasts)

Artificial, high‑cost structures such as sea walls, groynes, and rock armour designed to resist wave energy and protect coastlines.

Soft engineering (coasts)

Sustainable, nature‑based approaches such as beach nourishment and dune regeneration that work with natural processes.

Longshore drift

The transport of sediment along the coast by wave action, driven by prevailing wind direction and swash/backwash movement.

Sediment cell

A self‑contained coastal system where sediment is sourced, transported, and deposited within defined boundaries.

Shoreline Management Plan (SMP)

A strategic framework for managing risks to coastal communities and environments, outlining policies such as HTL, ATL, NAI, and MR.

Hold the Line (HTL)

A coastal management policy aiming to maintain the current coastline position using defences.

Managed Realignment (MR)

A policy allowing controlled retreat of the coastline to create natural buffers such as salt marshes.

Cost–benefit analysis (coastal management)

An assessment comparing the economic, social, and environmental costs of a management strategy with its expected benefits.

Stakeholders in coastal management

Groups affected by or involved in coastal decisions, including residents, businesses, environmental groups, and local authorities.

KORRMA structure (non‑UK case studies)

A framework covering Key characteristics, Opportunities, Risks, Resilience, Mitigation, and Adaptation.

Thermal expansion

The increase in ocean volume as water warms, contributing significantly to global sea‑level rise.

Define an open coastal system

A system with inputs, outputs, stores and transfers where energy and matter move across boundaries

What is dynamic equilibrium in coastal systems?

A state where coastal processes adjust to maintain balance despite external changes

Constructive wave characteristics

Low frequency, strong swash, weak backwash, deposition dominates

Destructive wave characteristics

High frequency, strong backwash, weak swash, erosion dominates

Define positive feedback in coastal systems

A process that amplifies change and pushes the system further from equilibrium

Define negative feedback in coastal system

A process that counteracts the original change, nullifies it, and restores equilibrium

Example of negative feedback on a beach

Storm erosion removes material which is later redeposited by constructive waves

Physical weathering processes in coastal environments

Frost shattering, salt crystallisation, exfoliation

Chemical weathering processes in coastal environments

Carbonation, oxidation, solution

Biological weathering processes

Root action, burrowing animals, organic acids

Define hydraulic action

Erosion caused by air compression in cracks due to wave impact

Define wave quarrying

Removal of loose blocks by breaking waves exerting pressure

Define wave quarrying

Removal of loose blocks by breaking waves exerting pressure

Sequence of stump formation

Crack then cave, arch, stack, stump.

Define littoral drift

Transport of sediment along the coast by longshore drift

Stages of sand dune succession

Embryo dunes, then fore dunes, then yellow dunes, grey dunes, climate climax.

What is a fjord?

A submerged U-shaped glacial valley with very steep sides, a flat or over-deeped floor, and often a shallow threshold (rock bar) at its mouth.

Examples of fjords (3)

1. Sognefjord, Norway — 1300m deep, classic over-deepened basin with a threshold.

2. Milford Sound, New Zealand — steep sides, dramatic U-shape, formed by powerful valley glaciers.

3. Patagonia, Chile — fjords formed by fast-flowing outlet glaciers from the Patogian Ice sheet.

The formation of a fjord — step 1.

Pre-glacial landscape: Starting point is a river valley (typically V-shaped) which often follows zones of structural weakness (faults, joints), making them ideal pathways for later glacial flow.

The formation of a fjord — step 2.

Glacial occupation of the valley: During cold periods (e.g. the last Glacial Maximum), a large valley glacier occupies the river valley. Glaciers have much greater erosive power than rivers (Basal sliding, abrasion where rock fragments embedded in the ice scour the bedrock, and plucking where freeze-thaw processes loosen and remove blocks)

The formation of a fjord — step 3.

Over‑deepening of the valley: Glacier moves downslope, and erosion is concentrated at the glacier’s base. The glacier erodes the valley into a U-shaped cross-section. In many fjords, the glacier becomes thicker and more powerful in its mid-section, causing overdeepening (the valley floor is eroded far below sea level) and the formation of a rock basin. At the mouth of the valley, where the glacier thins, erosion is less effective, leaving a threshold or sill.

The formation of a fjord — step 4.

Deglaciation: as climate warms, glacier melts and retreats. The over-deepened trough is left as a deep, steep-sided glacial valley with a rock basin (often hundreds of metres) below present sea level, and a shallow threshold at the mouth

The formation of a fjord — step 5.

Post-glacial sea-level rise (eustatic change): Melting ice sheets cause global (eustatic) sea-level rise. Rising seas flood the over-deepened trough, creating a long, narrow deep inlet. The threshold remains shallower, forming a partially enclosed basin.

The formation of a fjord, step 6, isostatic adjustment.

Land previously weighed down by ice begins to rebound (isostatic uplift). In many fjord regions, eustatic rise outpaced uplift, so the valleys remained submerged.

What is a dalmation coast also called?

Concordant drowned coastline

When do dalmation coasts form?

When submergence caused by eustatic sea-level rise floods a landscape of parallel anticlines and synclines, creating long, offshore islands and inlets aligned with the geological structure.

The first step of how a dalmation coast forms.

Initial geological structure: The coastline begins with folded sedimentary rocks, producing (Anticlines = upfolded ridges, Synclines = downfolded valleys). These folds run parallel to the coastline, making it a concordant coastline (structure and coast run in the same direction).

The second step of how a dalmation coast forms.

Pre-submergence landscape: Before sea-level rise, the landscape consists of elongated ridges (anticlines), parallel valleys (synclines). Rivers may occupy the synclines, deepening them through fluvial erosion.

The third step of how a dalmation coast forms

Eustatic Sea-level rise: A global rise in sea level typically occurs due to melting ice after glacial periods and thermal expansion of oceans. This is eustatic change, not isostatic.

The fourth step of how a dalmation coast forms

Submergence of the Landscape: Rising sea levels flood the synclines, turning them into long, narrow inlets and channels (which run parallel to the coast). The anticlines remain partially submerged, forming elongated offshore islands and chains of ridges separated by flooded valleys.

The fifth step of how a dalmation coast forms

The result: A submergent concordant coastline. The coastline now shows — parallel islands and inlets aligned with geological structure, a highly indented coastline, a pattern that resembles the Dalmation coast of Croatia.