Which of the following process is responsible for the formation of delta at a place where rivers meet the sea?

Coagulation

The correct answer is option 3. Coagulation.

To understand why coagulation is responsible for the formation of a delta at the confluence of a river and the sea, let us break down the process and its components in detail:

Coagulation refers to the process where fine particles suspended in a liquid aggregate to form larger particles or flocs, which then settle out of the suspension. Here’s how this process occurs in the context of delta formation:

Sediment Transport: Rivers carry sediments such as sand, silt, and clay particles. These particles are suspended in the river water due to the flow and turbulence of the river.

Decrease in Flow Velocity: When a river meets a larger body of water like an ocean or sea, the velocity of the river water decreases significantly. This reduction in velocity is due to the increase in the cross-sectional area of the water body and the effect of the tidal currents.

Particle Aggregation: The decrease in water velocity leads to the reduction in the ability of the river water to keep the fine sediments suspended. The suspended particles begin to settle out due to gravity and their increased tendency to aggregate.

Formation of Delta: As the suspended particles coagulate and settle, they accumulate at the river mouth, building up over time to form a delta. This accumulation of sediments creates the deltaic landform, characterized by its triangular or fan-like shape.

Other Processes for Comparison

To provide a clear understanding, let's contrast coagulation with the other processes listed:

Emulsification:

Emulsification is the process of stabilizing a mixture of two immiscible liquids (e.g., oil and water) to form an emulsion. Emulsifiers help disperse one liquid in another. Emulsification deals with liquid-liquid mixtures and is not related to sediment deposition or landform creation.

Colloid Formation:

Colloid formation involves creating a stable dispersion of fine particles (colloids) in a medium. Colloids are particles ranging from 1 nm to 1 µm in size, such as gels or sols.Colloid formation refers to the stability of small particles in a medium and does not directly relate to sediment settling or delta formation.

Peptization:

Peptization is the process of converting a precipitate back into a colloidal form using a peptizing agent. It involves dispersing previously aggregated particles. Peptization involves re-dispersing precipitates into a colloidal state and does not pertain to the deposition of sediments in rivers and deltas.

Detailed Process of Delta Formation

Sediment Transport: As a river flows towards a larger body of water, it transports sediment particles from upstream areas. The sediments can include various sizes, from coarse sand to fine silt and clay.

Reduction in Flow Velocity: Upon reaching the sea or ocean, the river’s flow velocity decreases significantly due to the large volume of water and the influence of tides and currents. The river’s momentum is reduced.

Coagulation and Deposition: As the flow slows, the energy available to keep the sediments in suspension is reduced. Fine particles start to clump together (coagulate) due to decreased flow and interactions with each other. These aggregated particles become heavy enough to settle out of the water.

Delta Formation: The deposited sediments accumulate over time, creating a delta. The shape and size of the delta depend on factors like sediment load, water flow patterns, and tidal influences.

The coagulation process, where particles aggregate and settle due to reduced flow velocity, is crucial for delta formation. Other processes like emulsification, colloid formation, and peptization do not apply to the sedimentation and landform creation that characterizes delta formation. Thus, coagulation is the process responsible for the formation of a delta where a river meets the sea.