Landforms

Landforms refer to features on the Earth’s surface that make up the terrain. Each geomorphic process and agent shapes the distinct characteristics of a landform, including its shape, size, and composition.Most geomorphic processes and agents work slowly, meaning landforms take a long time to develop. Once formed, landforms can gradually change in shape, size, and nature due to continuous geomorphic processes.

Landforms Created by Running Water

In regions with high rainfall, running water is a key geomorphic agent, actively shaping the landscape. Running water forms erosional landforms, typically in areas with youthful, fast-flowing rivers, especially those on steep gradients.

Erosional Landforms by Running Water:

• Valleys:
  Valleys begin as small rills, which evolve into deeper and wider gullies. These gullies continue to deepen, widen, and lengthen over time, forming valleys.
  
  • Types of Valleys:
    
    • Gorge: A deep, narrow valley with steep to vertical sides, often found in hard rock areas.
      
    • Canyon: Similar to a gorge but typically wider at the top than at the bottom, and formed in sedimentary rocks with horizontal layers.
      
  • Potholes and Plunge Pools:
    
    • Potholes are circular depressions formed by stream erosion and the abrasion of rocks.
      
    • Plunge pools are larger, deeper potholes formed by the intense impact of water and rock rotation, further deepening valleys.
      
  • Incised Meanders: These are deep, wide meanders cut into hard rock, forming when rivers rapidly cut into their beds.
    
  • River Terraces: These terraces represent ancient valley floors that have been eroded by the river. Paired terraces occur at the same elevation on both sides, while unpaired terraces are found at varying elevations.
    

Depositional Landforms by Running Water:

• Alluvial Fans: Formed when streams from mountain slopes break onto flatter plains, depositing coarse sediments in a cone-shaped deposit.
  
• Deltas: Similar to alluvial fans but located where rivers meet the sea, forming cone-shaped deposits made up of well-sorted materials.
  
• Floodplains: Flat areas next to rivers that are subject to periodic flooding, with distinct areas such as floodways (active channels) and flood fringes (inactive areas above the banks).
  
• Meanders: While not technically a landform, meanders are curves in the river course formed by lateral erosion. When a meander is cut off, it forms an oxbow lake.
  

Landforms Created by Groundwater

Groundwater is a potent erosional force, particularly in areas with limestone. Rainwater, mixed with carbon dioxide, forms carbonic acid, which dissolves rocks, especially limestone. This creates distinctive landforms called Karst Topography, which includes both erosional and depositional features.

Erosional Landforms by Groundwater:

• Swallow Holes and Sinkholes: Shallow depressions formed by the dissolution of limestone, with sinkholes being larger, funnel-shaped openings.
  
• Lapies and Limestone Pavements: Lapies are grooves or ridges formed by erosion of limestone, while limestone pavements are flat, exposed surfaces of eroded limestone.
  
• Caves: Formed in areas with alternating layers of limestone and other rocks, caves are common in karst regions.
  

Depositional Landforms by Groundwater:

• Stalactites and Stalagmites: Stalactites hang from cave ceilings, while stalagmites rise from the cave floor, formed by dripping water that deposits minerals.
  
• Pillars: Formed when stalactites and stalagmites fuse, creating columns of rock.
  

Landforms Created by Wind

Wind acts as a geomorphic agent, especially in arid regions. It erodes rocks by deflation (removing fine particles) and abrasion (scraping particles off surfaces). Wind transports eroded material in three ways: suspension, saltation, and surface creep.

Erosional Landforms by Wind:

• Wind removes particles to form deflation hollows and caves, which can evolve into caves.
• Wind erosion forms parallel troughs called yardangs, while it leaves isolated masses of resistant rock known as zeugen.
• Seasonal water covers playas, flat-bottomed depressions in deserts, leading to the deposition of salts and mud.
  

Depositional Landforms by Wind:

• Ripples: Small, wavelike formations on the surface created by wind blowing across loose sand.
  
• Loess: Windblown silt deposits that accumulate in certain regions.
  
• Dunes: Large sand hills built by the wind. Common types of dunes include:
  
  • Barchans: Crescent-shaped dunes.
    
  • Seif Dunes: Long, linear dunes.
    

Coastal Landforms

Coastal processes, such as wave action, continually shape coastal landforms. These processes can either erode or deposit material, depending on the coast’s configuration and whether it is advancing or retreating.

Erosional Coastal Landforms:

• Cliffs and Caves: Wave action forms cliffs as vertical rock faces. Weak spots in bedrock form caves, and arches collapse to leave behind stacks, which are pillars of rock.
  
• Sea Terraces: Raised rock terraces formed by wave-cut platforms.
  

Depositional Coastal Landforms:

• Beaches: Deposits of sediment, usually sand, that accumulate along shorelines.
  
• Spits and Bars: Sediment accumulates to form spits, which are long, narrow features attached to land at one end, while bars form as submerged or partially exposed ridges offshore.
  

Landforms Created by Glaciers

Glaciers significantly shape landscapes, especially in colder regions, by eroding, transporting, and depositing materials.

Erosional Landforms by Glaciers:

• Glacial Valleys: U-shaped valleys formed by glaciers that smooth and widen the land.
  
• Cirques: Bowl-shaped depressions formed by glaciers at the head of valleys.
  
• Horns and Serrated Ridges: Sharp, pointed peaks formed when glaciers erode multiple sides of a mountain.
  

Depositional Landforms by Glaciers:

• Glacial Till: Coarse, unsorted debris dropped by glaciers as they melt.
  
• Moraines: Ridges of debris left by glaciers, including terminal moraines at the glacier’s end, lateral moraines along its sides, and medial moraines formed in the center of valleys.
  
• Eskers and Drumlins: Eskers are ridges of sediment deposited by meltwater streams beneath glaciers, while drumlins are oval-shaped ridges formed by glacier movement.