It's tricky to pinpoint a *third* step in soil formation because it's a continuous process, not a series of distinct steps. However, we can break down the process into several key stages.

Here's a breakdown, and you can see where "the third step" might fit:

1. Weathering: This is the initial stage where bedrock is broken down by physical and chemical forces. Think of wind, rain, ice, temperature changes, and chemical reactions gradually chipping away at the rock. This produces parent material, the foundation of soil.

2. Biological Activity: This is where organisms start to transform the parent material.

* Pioneer species like lichens and mosses start to grow, releasing acids that further break down the rock.

* Decomposers like bacteria and fungi break down dead organisms, adding organic matter to the soil.

* Burrowing animals like earthworms and moles aerate the soil and mix in organic matter.

3. Development of Soil Horizons: This is where distinct layers, or horizons, begin to form within the soil profile. This happens due to:

* Movement of water: Water carries minerals and organic matter down through the soil, creating different layers with different properties.

* Accumulation of organic matter: This forms the topsoil layer (A horizon), rich in organic material and nutrients.

* Weathering and leaching: Minerals are leached from the upper layers and deposited in lower layers, creating distinct horizons.

4. Continued Evolution: Soil continues to evolve over time, influenced by factors like climate, topography, and human activities.

Therefore, "the third step" could be interpreted as the development of soil horizons, which is a significant stage in the process.

It's important to remember that soil formation is dynamic and continuous, so these stages overlap and interact constantly. There isn't a rigid "third step" – it's more of a gradual evolution with various factors at play.