mud banks

_Mud Banks _

*Definition:* Calm, turbid regions in coastal waters of Kerala, India.

*Characteristics:*

1. Form during southwest monsoon season.

2. Mud suspension causes high turbidity.

3. Water remains calm, wave-free.

4. Acts as barrier, preventing beach erosion.

5. Semi-circular shape, extending up to 6 fathom lines.

6. Dark green mud with foraminifera remains.

7. Fine texture (3/4 clay, 1/4 silt).

*Location:*

          1. Cochin
          2. Alleppy

          3. Between Cannanore and Quilon

*Unique Features:*

          1. Periodic phenomenon

          2. Not reported elsewhere in India

          3. Calm waters amidst monsoon season

*Composition:*

         1. Clay (<2µm or <0.002 mm): 75%

         2. Silt (2µm to 20µm or 0.002 mm to 0.02 mm): 25%

*Importance:*

1. Coastal protection

2. Erosion prevention

3. Unique geological feature

*Mud Bank Formation Mechanism*

*Step 1: Underground Discharge*

1. Increased water level during monsoon

2. Hydraulic pressure builds up

3. Bottom mud dispelled and forced into the sea

4. Mud volcanizes, cones, and bubbles up to the surface

*Step 2: Wave Action*

1. Pre-monsoon winds generate high waves

2. Waves feed energy to keep mud in suspension

3. Mud from sea bed remains suspended

*Step 3: Upwelling*

1. Upwelling occurs between 20-30m depth

2. Divergence near the bottom lifts fine mud

3. Vertical acceleration suspends mud particles

*Step 4: Flocculation and Deflocculation*

1. Suspended particles deflocculate (low salinity)

2. Particles remain suspended (salinity < 2.5 ppt)

3. Flocculation occurs (salinity > 20 ppt)

4. Deflocculation takes place (salinity drops)

*Mud Bank Formation*

1. Suspended mud particles converge

2. Calm, turbid region forms

3. Mud bank emerges, extending seaward

4. Semi-circular shape, up to 6 fathom lines

*Theories:*

1. John Rhode (1886): Underground discharge

2. Du-cane: Wave action

3. Ramasastry and Myrland (1959): Upwelling

4. Flocculation and deflocculation

                     Or

Here's a simplified explanation of the mud bank formation process:

*Step 1: Underground Discharge*

- Rainwater and floodwater from backwaters flow into the sea.

- Increased water pressure pushes mud from the sea floor upwards.

*Step 2: Wave Action*

- Pre-monsoon winds generate waves.

- Waves stir up and suspend mud particles from the sea floor.

*Step 3: Upwelling*

- Deep water rises to the surface, carrying fine mud particles.

- Mud particles are lifted and suspended in the water column.

*Step 4: Flocculation and Deflocculation*

- Freshwater from rivers and rain mixes with seawater.

- Salinity drops, causing mud particles to deflocculate (break apart).

- Deflocculated particles remain suspended in the water.

*Step 5: Mud Bank Formation*

- Suspended mud particles converge and accumulate.

- Calm, turbid region forms near the coast.

- Mud bank emerges, extending seaward in a semi-circular shape.

This process occurs during the southwest monsoon season, typically between June and September.

*Theories on Calmness:*

1. *W. King (1881)*: Oil presence dampens waves.

2. *Keen and Russel*: Mud suspension increases water viscosity, damping waves (liquid mud).

Result:

- Mud bank forms, protecting the coast from erosion.

- Calm, turbid water region extends up to 6 fathom lines.