Coastal Landforms, Aeolian Processes, Karst, and Glacial Features

Posted on Jan 23, 2025 in Geology

Coastal Landforms

Sea water transports particles, driven by waves, tides, and currents. The accumulation of sediments along coastlines rapidly forms various features:

  • Beaches: Formed in the interior of bays, where waves lose force.
  • Coastal bars: Similar to beaches, but not fully joined to the coast, often long and visible or submerged.
  • Reefs/spits: Joined to the coast at one end.
  • Barrier islands: Not joined to the coast.
  • Land-tied islands: Join the coast with a nearby outcrop.
  • Coastal pools: Coastal lakes closed off by sandbanks.

Aeolian Processes

The geological action of wind involves erosion, transport, and sedimentation. Air in movement has two erosive actions:

  • Deflation: Selective carrying of small particles, leaving larger ones behind.
  • Aeolian abrasion: Wearing away of rocks by the impact of wind-carried particles.

Aeolian sedimentation results in:

  • Dunes: Live or active accumulations of sand that move across the ground. They have a gentle slope on the windward side and a steeper slope on the leeward side.
  • Loess deposits: Fine particles carried long distances and deposited when the wind loses force.

Particles are transported by traction, saltation, or suspension, depending on their weight and wind force.

Geological Action of Living Beings

Living beings have both destructive and constructive geological actions:

  • Destructive actions:
    • Mechanical action: Breaking up by plant roots and animals.
    • Chemical action: Decomposition by microorganisms.
  • Constructive action: Significant in landscape modification.

Human activities also modify the landscape through both constructive and destructive actions.

Karstic Modeling

Karstic modeling is a special land relief formation due to torrential fluvial processes in limestone-rich areas. Water dissolves the chalk, creating typical shapes:

  • Simas and caverns: Formed by water dissolving limestone.

A karst region is where this type of erosion is found. The formation stages include:

  1. Water circulates over the limestone surface.
  2. Water infiltrates cracks, dissolving limestone and forming depressions.
  3. Water digs channels, forming caverns.
  4. Water drips in caverns, forming stalactites and stalagmites.
  5. Erosion continues until an impermeable layer is reached, forming a stable water current.

Glaciers

Glaciers are large masses of ice in constant movement, descending from higher zones. Types include:

  • Alpine glaciers: Long tongues of ice moving about one meter a day.
  • Pyrenean glaciers: Similar to Alpine glaciers, but without a tongue.
  • Pack ice glaciers: Immense frozen masses with tongues ending in the sea.

Glacial erosion is due to friction between ice and rocky materials. Glacial valleys are U-shaped, unlike V-shaped fluvial valleys. Transport and sedimentation result in moraines, accumulations of stony pebbles deposited on the sides and bottom of the glacier.