What type of particles settle out first in sedimentation?

In sedimentation, the particles that settle out first are typically the larger, most dense, and roundest particles. This behavior can be explained by gravity and particle dynamics during the sedimentation process.

Larger particles have a greater mass, which allows them to overcome the resistance of water or other fluids more effectively than smaller particles. Additionally, denser particles have a higher weight relative to their volume, which contributes to their ability to sink faster. Round particles also experience less drag in the fluid compared to angular or irregularly shaped particles, as their smooth surface allows them to move through the fluid more easily.

As a result, during sedimentation, the particles will settle in a specific order based on size and density, with those that are larger and denser settling down first. The smaller, finer particles will take longer to settle, often remaining suspended in the fluid for an extended period before eventually settling out, especially if the fluid is calm. Thus, this process leads to the stratification of sediments, with larger and denser particles being found near the bottom of the sediment layer.