Natural Agencies and Landforms

• Natural Agencies

  • Also known as geomorphic agents
  • the natural forces that shape the earth’s surface through processes of:

  EROSION TRANSPORTATION DEPOSITION
• Erosion is the process by which rocks, soil or sediment are removed from one place to another.
• Deflation Process - Removal of loose sediments in an area by wind.
• Abrasion Process - Process that causes larger particles to break down into smaller ones from repeated impacts by sediments suspended in the air.
• Attrition Process - The particles during transportation collide and break down into finer particles.
• Transportation - Movement of eroded materials from their source areas to new locations.
• Suspension Process - Transportation of particles with the help of the wind. The particles remain in suspension while being transferred into one place to another.
• Saltation Process - The transportation of minerals in a bouncing manner within the surface.
• Traction Process Rolling or creeping usually happens to larger particles on the earth’s surface.
• Deposition - The process whereby transported material is laid down at its final destination.
• 3 Geomorphic agents - These geomorphic agents bring change to the earth’s landforms.

  • Wind
  • Rivers
  • Glaciers
• Wind - is the natural movement of air or other gases relative to a planet’s surface.
• Creeping - Rolling or dragging of salt particles across the surface by aeolian forces.
• Ventifact

  • A landform formed by wind.
  • Comes from Latin word “Ventus” meaning wind.
  • A stone that had been worn out, polished, or faceted as a result of erosion by windblown sand, specifically the abrasion.
• Sand Dune - A hill made up of loose sand built into mounds by the action of the wind. It can be found in deserts and coastal areas.
• Longitudinal Dune -  large, elongated dune lying parallel to the prevailing wind direction.
• Star Dune -  a type of transverse dune with arms radiating from its summit.
• Transverse Dune -  Substantial, highly asymmetrical, and extended dune positioned perpendicular to the prevailing wind direction.
• Barchan Dune - Crescent-shaped sand dunes with horns pointing downwind, forming in areas with limited sand and steady wind direction.
• Pedestal rocks

  • are also called mushroom rocks. 
  • These rocks are mainly formed by the wind exploit.
• River - is a large, natural stream of flowing water.
• Hydraulic Action - This is the sheer power of the water as it smashes against the river banks.
• Attrition - When rocks that the river is carrying knock against each other. 
• Solution - When the river water dissolves certain types of minerals into smaller pieces.
• Traction - A method of transportation for large stones or boulders in a river. The stones are rolled along the river bottom by the water as they are too large to transport in the water.
• Saltation - Small rocks or pebbles which are too big to be carried within the water are transported and bounce along the bottom of the river bed
• Suspension - Lighter sediment is suspended (carried) within the water.
• Deposition - When the river loses energy, it drops any of the material it has been carrying.
• V-shaped valleys - are formed as rivers transport material along their beds, especially by traction and saltation.
• Waterfalls - form when a river flows over hard rock atop softer rock, which erodes faster, creating a vertical drop. 
• Pothole

  • is a smooth, bowl-shaped or cylindrical hollow, generally deeper than wide, found carved into the rocky bed of a watercourse.
  • typically formed through a natural erosional process known as abrasion.
• Glaciers - are moving bodies of ice that can change entire landscapes.
• Glacier erosion - is the process of wearing away the land by the movement of land masses of ice.
• Freeze-thaw weathering - Erosion by glaciers. Occurs when rocks are porous (contain holes) or permeable (allow water to pass through).
• Plucking - Erosion by glaciers. As the glaciers fall downhill, pieces of rocks and particles come along with it.
• Abrasion -Erosion by glaciers. Process that causes larger particles to break down into smaller ones from repeated impacts by sediments suspended in the air.
• Cirques - are bowl-shaped, amphitheater-like depressions that glaciers carve into mountains and valley sidewalls at high elevations.
• Kettles - Form when a block of stagnant ice (a serac) detaches from the glacier. 
• Horns - are pointed peaks that are bounded on at least three sides by glaciers.