This would be primary succession. Primary succession is succession starting from bare rock. Succession may start with weathering of the rock to create small pockets of lose soil. Seeds of pioneer plants may be carried by the wind to fall into pockets of soil with sufficient moisture to allow germination. The growth of pioneer plants will further break up the bare rock, creating a deeper layer of soil. As the plants grow, dead leaves and roots enrich the soil with organic content. Small animals start to colonise the area, such as gophers, who further break up and enrich the soil. The plants change from pioneer plants to plants of a specific biome. Succession will continue in this fashion until until an equilibrium is achieved.
