Johnson’s Classification of Shorelines

D.W. Johnson presented a genetic classification of shorelines based on:

1. Nature of the coastland before any sea-level change.
2. Emergence or submergence of the coastline due to changes in sea level.

He classified shorelines into five main types:

1. Shoreline of Emergence: Coastlines Rising from the Sea

• Cause:
  • Formed due to either:
    • Fall in sea level, or
    • Upliftment of landmass (tectonic movement).
  • This may occur due to climatic factors (melting of ice) or tectonic forces (earthquakes, faulting).
• Features:
  • Bars, spits, lagoons, salt marshes, beaches, sea cliffs, and arcs.
  • Generally, the coast appears to advance into the sea due to land upliftment.
• Examples:
  • East coast of India (especially the southeast coast) shows evidence of emergence.
  • Southern Kerala coast on the west coast of India is also an emergent coast.
• Interesting Fact:
  • West coast of India is partially emergent (Kerala) and partially submerged (Mumbai) due to faulting.

✅ Why Important?

• Emergent coasts provide new land for human settlements, agriculture, and infrastructure.

2. Shoreline of Submergence: Sinking of Coastal Land

• Cause:
  • Formed due to either:
    • Rise in sea level, or
    • Subsidence of landmass (tectonic movement).
  • May happen due to climatic changes (melting of polar ice caps) or tectonic activity (earthquakes, faulting).
• Features:
  • Ria Coasts: Submerged river valleys, giving a highly irregular coastline. Example: Southwest Ireland.
  • Fjords: Glacially eroded U-shaped valleys submerged under seawater after ice melts. Example: Norway coast.
  • Drowned lowlands: Coastal plains submerged by seawater.
• Example:
  • Mumbai coastline (India) — submergence due to faulting.
  • Norwegian Fjords — deep, narrow, steep-sided sea inlets formed by glacial erosion.

✅ Why Important?

• Submerged coasts offer natural harbors, deep-sea ports, and scenic beauty, boosting tourism and trade.

3. Neutral Shoreline: Coastlines Built by Sediment Deposition

• Cause:
  • Formed neither by emergence nor submergence.
  • Created solely by the deposition of sediments brought by rivers, waves, and coastal currents.
• Features:
  • Sandy beaches, sand dunes, deltas, lagoons, and coastal marshes.
  • These shorelines have no evidence of submergence or emergence.
• Example:
  • Sundarbans Delta (West Bengal) — formed by river sediment deposition.
  • Chilika Lake (Odisha) — formed by marine deposition.

✅ Why Important?

• Highly fertile areas suitable for agriculture, fisheries, and tourism.

4. Compound Shoreline: Mixed Impact of Emergence and Submergence

• Cause:
  • Formed due to both emergence and submergence over different geological timescales.
  • These coasts show mixed features of both types.
• Features:
  • Presence of sea cliffs (emergence), fjords (submergence), beaches, and coastal lagoons.
• Example:
  • Norway and Sweden coastlines show evidence of both glacial submergence and land upliftment.
  • Western Ghats (India) — partially submerged and partially emergent.

✅ Why Important?

• These coasts offer diverse landscapes, making them ideal for harbors, tourism, and biodiversity.

5. Fault Shoreline: Result of Tectonic Movements

• Cause:
  • Formed due to faulting (cracking) of the Earth’s crust, where:
    • One block is uplifted (emergent coast).
    • Another block is downthrown (submerged coast).
• Features:
  • Steep cliffs, deep coastal waters, and narrow beaches.
  • Uneven coastlines due to block faulting.
• Example:
  • Southern coastline of India — the western part (Mumbai) submerged while the eastern part (Tamil Nadu) slightly tilted.
  • California coast (USA) — major fault shoreline due to tectonic movements.

✅ Why Important?

• Fault shorelines create deep sea harbors, steep cliffs, and geological diversity.
• However, they are highly prone to earthquakes and tsunamis.

✅ Quick Recap Table

✅ Why is This Important for India?

• East Coast of India → Emergent Coast (Tamil Nadu, Andhra Pradesh).
• West Coast of India → Mixed Coast (Mumbai submerged, Kerala emerged).
• Fault Coastline → Southern Coast of India due to tectonic faulting.
• Sundarbans Delta → Neutral Shoreline formed by sediment deposition.

✅ Exam Hack:

• If the coastline has deep sea ports → Submergent coast.
• If it has beaches, sand dunes → Neutral coast.
• If it has cliffs and bars → Emergent coast.
• If tectonic cracks are visible → Fault coast.
• If mixed landforms appear → Compound coast.

💡 Pro Tip:

• India’s diverse coastline is a perfect example of Johnson’s classification.
• If you understand why coasts rise or sink, you can easily relate this to harbors, fishing zones, tourism, and coastal disasters in real life. 🌊🌍