Rock density does not directly affect the formation of "war layers". It seems you might be thinking of "warves", which are thin layers of sediment deposited in lakes and other quiet water bodies. These layers often exhibit alternating light and dark bands, and they are formed by seasonal changes in sedimentation rates.

Here's how the process works:

* Summer: Warmer temperatures lead to increased biological activity in the lake, resulting in the deposition of organic matter and fine sediment. This creates a darker layer.

* Winter: Colder temperatures and reduced biological activity result in less sediment deposition. The layer formed in winter is typically lighter in color due to the absence of organic matter.

Rock density plays a very minor role in the formation of varves:

* Erosion: Rocks with lower density may erode more easily, contributing more sediment to the lake. This effect is usually negligible compared to other factors like seasonal changes.

* Sediment transport: Rock density affects the settling rate of particles. Heavier particles settle faster, potentially influencing the thickness of varve layers. However, this is a minor factor compared to the seasonal variations in sedimentation.

Instead of rock density, the following factors are more crucial in varve formation:

* Climate: Seasonal temperature and precipitation variations are the primary drivers of varve formation.

* Biological activity: Seasonal changes in algae blooms, plant decomposition, and insect activity contribute to the differing coloration of varves.

* Water currents: Currents can influence sediment deposition and affect the thickness and uniformity of varves.

In conclusion, while rock density can indirectly affect the supply of sediment to lakes, it's not a primary factor in the formation of varves. The primary drivers are seasonal changes in climate, biological activity, and water currents.