Coastal Environments and Physical Processes

Vocabulary flashcards covering physical processes, marine and sub-aerial mechanisms, coastal weathering and mass movement, wave dynamics, and coastal erosional and depositional landforms.

Base flow

The 'normal' discharge of a river during non-storm conditions.

Storm flow

The additional discharge of a river that occurs as a direct result of a rainstorm.

Weathering

The breakdown, decay, and disintegration of rocks in situ above the ground surface, driven by elements of the weather such as rainfall and temperature changes.

Physical weathering

Mechanical processes that break rocks down into smaller pieces without chemical change, including temperature fluctuations, salt crystal growth, and freeze-thaw action in rock cracks.

Freeze-thaw weathering

A physical weathering process where water enters cracks in rocks, freezes and expands when temperatures drop below freezing, and later thaws, gradually forcing the rock apart.

Chemical weathering

The decay and disintegration of rocks caused by chemical reactions, largely occurring when slightly acidic rainwater seeps into porous rocks.

Biological weathering

The breakdown and splitting of rocks caused by living organisms, such as tree and plant roots growing into rock cracks.

Mass movement

The downward movement of weathered material or cliff-face rock under the direct influence of gravity.

Slumping

A form of mass movement where the base of a cliff or valley slope is undercut and weakened, causing saturated weathered material to slide downwards, aided by water adding weight and acting as a lubricant.

Soil creep

The very slow, gradual downhill movement of weathered material and soil under the influence of gravity.

Rockfall

A rapid form of mass movement where fragments of rock detach from a cliff face and fall freely under gravity.

Erosion

The wearing away and removal of rock or sediment by active natural agents such as moving water, waves, wind, and rain.

Hydraulic action

An erosional process where the sheer force of water or breaking waves strikes a rock surface, trapping and compressing pockets of air into cracks until the rock shatters.

Abrasion

An erosional process where stones, pebbles, and sediment carried by water or waves are hurled or rubbed against rock surfaces, wearing them away with a sandpaper-like effect.

Corrosion (Solution)

An erosional process in which soluble minerals within coastal cliffs or river channel walls are chemically dissolved by moving water or seawater.

Attrition

A process where rock fragments and pebbles carried by waves or rivers collide with one another, gradually breaking down into smaller, smoother, and rounder particles without eroding the bedrock directly.

Transportation

The movement of detached sediment, known as the load, through a coastal or river system by moving water.

Traction

A method of transport where large, heavy boulders and rocks are rolled along the channel bed or sea floor by water flow.

Saltation

A method of transport where small boulders, pebbles, and coarse grains bounce along the river bed or sea bed in a series of leaps.

Suspension

A method of transport where fine, light mineral particles are held up and carried within the body of flowing water.

Coast

The transition zone between the land and the sea.

Coastline

The actual physical boundary or frontier between the land and the sea.

Onshore zone

The landward section of the coastal environment that can extend up to $60\,\text{km}$ inland from the coastline.

Offshore zone

The seaward section of the coastal environment that extends as far as $370\,\text{km}$ out to sea from the coastline.

Fetch

The distance over open sea and the length of time across which wind blows continuously to generate waves.

Swash

The forward rush of water that surges up a beach face when a wave breaks.

Backwash

The movement of water draining back down the beach slope toward the sea under the pull of gravity.

Constructive waves

Low-frequency, long-wavelength waves with shallow gradients whose swash is stronger than their backwash, causing net deposition and building up the beach profile.

Destructive waves

Steep, tall waves with short wavelengths whose backwash is stronger than their swash, scouring and dragging beach material away out to sea.

Longshore drift

The zig-zag transportation of sediment along a beach face, driven by waves approaching at an angle with the prevailing wind and backwash retreating directly down the slope at right angles.

Deposition

The settling out and dropping of transported rock, sand, mud, and shingle when wave energy or river flow velocity decreases.

Concordant coast

A coastline where the underlying rock bands and geological strata run parallel to the direction of the sea, often creating relatively straight coastlines.

Discordant coast

A coastline where alternating bands of hard and soft rock outcrop at right angles to the sea, leading to differential erosion that produces headlands and bays.

Headland

A promontory of resistant, hard rock (such as chalk or limestone) that projects out into the sea because it erodes much slower than surrounding weaker rocks.

Bay

A curved, sheltered coastal inlet formed between headlands where bands of softer, weaker rock (such as clay or sand) are eroded rapidly by wave attack.

Wave-cut notch

A distinct indentation eroded into the foot of a cliff between high and low tide levels by the concentrated hydraulic action and abrasion of destructive waves.

Wave-cut platform

A gently sloping, rocky bench left exposed at low tide at the foot of a cliff as repeated basal notching and overhang collapse force the cliff to retreat inland.

Cave

A coastal cavity carved into a headland along faults or natural joints by hydraulic action and abrasion.

Arch

A coastal feature formed when wave erosion cuts completely through a cave on a headland or when two caves eroding from opposite sides break through and connect.

Stack

An isolated, steep-sided pillar of rock left standing alone offshore after wave undercutting and sub-aerial weathering cause the roof of an arch to collapse.

Stump

A low, eroded remnant of a stack that has collapsed under basal wave erosion, often visible only at low tide.

Beach

The most common depositional coastal landform, composed of loose sand, shingle, and pebbles accumulated between the storm-beach limit and low-tide mark.