1.1.7 Aolian, fluvial and biotic processes

What are Aeolian processes?

The action of wind transporting, eroding, and depositing material.

What is suspension in terms of wind transport?

Finer sand particles moved by the wind, high in the air, unaffected by gravity.

What is surface creep?

Larger particles move along the ground as they are too heavy to be picked up by the wind.

Describe saltation.

A process where wind causes turbulence that dislodges sand particles, allowing them to bounce and be picked up by the wind.

What are coastal dunes?

Dunes formed where beach sands are reworked by the wind, typically originating from seabed and river materials.

What conditions favor dune evolution?

Macro-tidal environments, onshore winds, and areas of net sediment accumulation.

What are the optimum conditions for dune formation?

Abundant sand supply, low beach gradient, macro-tidal range, strong prevailing winds, space for development, and presence of vegetation.

What leads to the formation of parabolic dunes?

The erosion of vegetated sand due to strong winds resulting in blowouts.

How do blowouts demonstrate positive feedback in dune systems?

Loss of vegetation leads to less friction, increasing wind speed and sand mobility, making re-establishment of vegetation harder.

What initiates the formation of a sand dune?

Constructive waves depositing sediment on the beach and winds moving sand inland.

Define ridges in the context of sand dunes.

Lines of dunes that are parallel to the coast.

What are slacks in sand dunes?

Hollows found between dune ridges.

What characterizes grey dunes?

Older dunes with a humus layer created by decomposing organic matter, appearing grey.

What are yellow dunes?

Younger dunes that lack a humus layer.

What are embryo dunes?

The youngest dunes in the early stages of formation.

What is a fore dune?

Dune ridges that are closest to the sea.

Define fixed dunes.

Older dunes that have become stabilised with vegetation.

What is a blow-out in the context of sand dunes?

An area eroded by wind due to the removal of its protective layer of vegetation.

What are tidal flats?

Level muddy areas bordering an estuary, characterized by low-energy conditions.

What process primarily creates tidal mudflats?

Deposition of fine sediment.

Describe salt marshes.

Gently sloping, vegetated areas of intertidal mudflats found in low-energy locations.

What are the characteristics of salt marshes?

Sheltered areas with salt-tolerant plants, channels, and rills.

What role do coral reefs play in coastal ecosystems?

Calcium carbonate structures built by coral polyps, essential for marine biodiversity.

How do mangroves develop?

Small trees grow in deposited fine sediments on tropical coastlines, allowing deep roots to survive salty conditions.

What environmental conditions are essential for coral reefs?

Sheltered areas, weak currents, ample light for photosynthesis, and warm temperatures.

What is the significance of biotic processes in coastal environments?

They are essential for the formation and sustainability of ecosystems like coral reefs and mangroves.

List the non-marine influences in coastal environments.

Wind action, river action, and biotic processes.

What factors are necessary for sand dune formation?

Supply of sand, low beach gradient, exposed beach area, strong winds, space for development, and vegetation.

How do dunes primarily form?

Primarily by saltation as wind moves sediment until its speed decreases.

What characterizes tidal flats in estuarine environments?

Extensive unvegetated intertidal areas with micro-features such as channels and rills.

Describe the slope of salt marsh coastal systems.

A near-horizontal platform that slopes gently seaward.