Coastal Processes and Landscapes

Flashcards covering coastal weathering, mass movement, wave types, erosion, transportation processes, and deposition from the Coastal Landscapes in the UK unit.

What is the difference between weathering and erosion?

Weathering is the breakdown of rocks in situ (where they are), whereas erosion occurs when rocks are broken down and carried away by something, such as seawater.

What is mechanical weathering?

The breakdown of rock without changing its chemical composition.

How does freeze-thaw weathering cause coastal rocks to break down?

When temperatures alternate above and below $0\,^\circ\text{C}$, water enters cracks in rocks (such as granite). The water expands as it freezes, exerting pressure, and contracts when thawing. Repeated cycles widen the cracks and cause the rock to break up.

What is chemical weathering?

The breakdown of rock by changing its chemical composition.

How does carbonation weathering break down rock?

In warm and wet conditions, carbon dioxide dissolved in rainwater creates a weak carbonic acid that reacts with and dissolves rocks containing calcium carbonate, such as carboniferous limestone.

What is mass movement and when does it occur?

It is the shifting of rocks and loose material down a slope (such as a cliff), which occurs when the force of gravity acting on the slope exceeds the force supporting it.

Why is mass movement more likely to occur when slope material is full of water?

Water acts as a lubricant and adds extra weight to the material.

What is a scarp?

A steep cut created in the side of a slope when material shifts during mass movement.

How do slides, slumps, and rockfalls differ in their movement?

In slides, material shifts in a straight line along a slide plane; in slumps, material rotates along a curved slip plane; and in rockfalls, material breaks up (often along bedding planes) and falls down a slope.

How does hydraulic power wear away coastal rock?

Waves crash against rock and compress air inside cracks, creating pressure; repeated compression widens the cracks and causes pieces of rock to break off.

What occurs during the process of coastal abrasion?

Eroded particles carried in the water scrape and rub against rock surfaces, removing small pieces.

What occurs during the process of coastal attrition?

Eroded particles in the water collide with each other, breaking into smaller pieces and becoming progressively more rounded.

How does longshore drift move material along the coast?

Waves driven by the prevailing wind hit the coast at an oblique angle, swashing material up the beach in that direction. The backwash then pulls material straight down the beach at a right angle, causing sediment to zigzag along the shoreline.

What are the four water transportation processes classified by sediment size and energy?

Traction (large boulders pushed along the sea bed), saltation (pebble-sized particles bounced along the sea bed), suspension (small particles like silt and clay carried in the water), and solution (dissolved soluble materials like limestone carried along).

What is wave fetch and how does it affect wave strength?

Fetch is the distance wind blows across the surface of the sea; a greater fetch produces a more powerful wave.

What causes a storm surge?

A storm surge is a temporary rise in sea level caused when strong storm winds push water onshore.

What are the characteristics of destructive waves?

Destructive waves have a high frequency, are high and steep, and possess a backwash that is more powerful than their swash, causing sediment to be removed from the coast.

What are the characteristics of constructive waves?

Constructive waves have a low frequency, are low and long, and have a swash that is more powerful than their backwash, causing sediment to be deposited on the coast.

When does coastal deposition occur?

Deposition occurs when water carrying sediment loses energy and slows down, causing it to drop material.