In sedimentation, the layers settle in order of density, with the densest material settling to the bottom first and the least dense material settling to the top.

Here's a breakdown:

* Density: Density is a measure of how much mass is packed into a given volume. Denser materials have more mass packed in the same space.

* Sedimentation: This is the process where particles in a fluid (like water or air) settle out due to gravity. The heavier (denser) particles sink faster, leading to layered sedimentation.

Example:

Imagine a mixture of sand, gravel, and leaves in a container of water.

1. Gravel: Gravel is the densest material, so it will sink to the bottom first.

2. Sand: Sand is less dense than gravel, so it will settle on top of the gravel layer.

3. Leaves: Leaves are the least dense, so they will float on top of the sand and gravel.

Important Note: This is a simplified explanation. Other factors like particle size, shape, and the properties of the fluid can also affect the order of sedimentation.