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

Shoreline Type	Cause of Formation	Major Features	Examples
Emergence	Fall in sea level or land upliftment	Sea cliffs, bars, spits, lagoons, beaches.	East Coast of India, Kerala Coast
Submergence	Rise in sea level or land subsidence	Ria coasts, Fjords, drowned lowlands.	Mumbai Coast, Norway Fjords
Neutral	Deposition of sediments	Beaches, sand dunes, deltas, coastal marshes.	Sundarbans Delta, Chilika Lake
Compound	Both emergence and submergence	Mixed features like cliffs, fjords, beaches.	Norway, Sweden, Western Ghats
Fault	Result of tectonic faulting	Steep cliffs, fault block coast, deep waters.	Southern India Coast, California Coast

✅ 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. 🌊🌍