Landforms and their Evolution

Introduction

• The Earth's surface undergoes continuous changes due to geomorphic processes, which result in different landforms.

• Landforms: Natural features on the Earth's surface, shaped over time.

• Two Types of Geomorphic Processes:

  1. Endogenic Processes (Internal forces) – Driven by heat from Earth's interior.

     • Example: Tectonic movements leading to mountain formation (Himalayas, Andes).

  2. Exogenic Processes (External forces) – Driven by external agents like wind, water, ice, and waves.

     • Example: Erosion by rivers creating valleys (Grand Canyon).

Geomorphic Agents and Processes

• Geomorphic Agents: Running water, glaciers, wind, sea waves, and groundwater.

• Processes Involved:

  • Erosion – Removal of surface material by agents like rivers, glaciers, wind.

    • Example: River erosion carving out the Grand Canyon, USA.

  • Transportation – Movement of eroded material by natural forces.

    • Example: Sediment carried by the Ganga River.

  • Deposition – Accumulation of eroded material in new locations.

    • Example: Formation of the Sundarbans delta.

Fluvial Landforms (Landforms by Running Water – Rivers)

Erosional Landforms by Rivers

1. V-Shaped Valleys:

   • Formed due to vertical erosion in youthful river stages.

   • Example: Indus River Valley in Ladakh.

2. Gorges:

   • Deep, narrow valleys formed by intense downcutting.

   • Example: Kali Gandaki Gorge in Nepal.

3. Canyons:

   • Larger and wider than gorges, with steep sides.

   • Example: Grand Canyon, USA (formed by the Colorado River).

4. Waterfalls:

   • Formed where a river flows over resistant rock layers.

   • Example: Jog Falls, Karnataka (Sharavati River).

Depositional Landforms by Rivers

1. Alluvial Fans:

   • Cone-shaped deposits formed at foothills.

   • Example: Himalayan foothills (where rivers like the Kosi deposit sediments).

2. Floodplains:

   • Flat plains created by seasonal floods depositing silt.

   • Example: Indo-Gangetic Plains.

3. Oxbow Lakes:

   • Crescent-shaped lakes formed by river meandering.

   • Example: Lakes along the Mississippi River, USA.

4. Deltas:

   • Triangular landforms at river mouths due to sediment accumulation.

   • Example: Sundarbans Delta (Ganga-Brahmaputra River System).

Glacial Landforms (Landforms by Moving Ice – Glaciers)

Erosional Landforms by Glaciers

1. Cirques:

   • Bowl-shaped depressions at mountain tops.

   • Example: Cirques in the Alps.

2. U-Shaped Valleys:

   • Glaciers erode valleys into a U-shape with steep sides.

   • Example: Glacier National Park, USA.

3. Horns:

   • Sharp, pyramid-like peaks formed by erosion from multiple glaciers.

   • Example: Matterhorn, Alps.

Depositional Landforms by Glaciers

1. Moraines:

   • Glacial debris (rocks, soil) deposited by melting glaciers.

   • Example: Terminal moraines in the Himalayas.

2. Drumlins:

   • Smooth, egg-shaped hills formed by glacial deposits.

   • Example: Drumlin fields in Canada.

3. Eskers:

   • Sinuous ridges of sand and gravel left by meltwater streams beneath glaciers.

   • Example: Eskers in Scandinavia.

Aeolian Landforms (Landforms by Wind – Common in Deserts)

Erosional Landforms by Wind

1. Yardangs:

   • Long, narrow ridges sculpted by wind erosion.

   • Example: Yardangs in the Lut Desert, Iran.

2. Deflation Hollows:

   • Depressions created by wind removing loose material.

   • Example: Qattara Depression, Egypt.

Depositional Landforms by Wind

1. Sand Dunes:

   • Hills of sand deposited by wind movement.

   • Example: Thar Desert (Rajasthan, India).

2. Loess:

   • Fine dust deposits carried by wind over large areas.

   • Example: Loess Plateau, China.

Coastal Landforms (Landforms by Sea Waves – Coastal Areas)

Erosional Landforms by Waves

1. Sea Cliffs:

   • Vertical rock faces formed by wave erosion.

   • Example: White Cliffs of Dover, UK.

2. Wave-Cut Platforms:

   • Flat areas left behind after wave erosion.

   • Example: Wave-cut platforms along the California coast, USA.

3. Sea Arches and Stacks:

   • Erosion forms caves, then arches, which eventually collapse into stacks.

   • Example: Old Harry Rocks, UK.

Depositional Landforms by Waves

1. Beaches:

   • Sandy or pebbly shorelines formed by wave deposition.

   • Example: Marina Beach, Chennai.

2. Bars and Spits:

   • Narrow ridges of sand formed by wave action.

   • Example: Chilika Lake Spit, India.

3. Tombolos:

   • Deposits connecting islands to the mainland.

   • Example: St. Michael’s Mount, UK.

Karst Landforms (Landforms by Groundwater – Common in Limestone Areas)

• Formed due to chemical weathering of limestone (carbonation).

Erosional Karst Landforms

1. Sinkholes:

   • Circular depressions due to limestone dissolution.

   • Example: Great Blue Hole, Belize.

2. Limestone Caves:

   • Underground caves formed by dissolved limestone.

   • Example: Borra Caves, India.

Depositional Karst Landforms

1. Stalactites:

   • Icicle-like formations hanging from cave ceilings.

2. Stalagmites:

   • Pillar-like formations rising from the cave floor.

3. Pillars:

   • Formed when stalactites and stalagmites join.

   • Example: Ajanta & Ellora Caves, India.

Significance of Landforms

• Agriculture – Fertile floodplains (e.g., Indo-Gangetic Plains).

• Water Resources – Rivers, lakes (e.g., Himalayas as water sources).

• Natural Hazards – Landslides, floods, earthquakes.

• Tourism – Attraction sites (e.g., Grand Canyon, Alps).