Soil forming factors

The beginning: From rock to soil

Every soil begins with a geological foundation. At its “birth” lies rock – either solid bedrock or loose sediments transported by wind, water, ice, or gravity. In soil science, this starting material is called parent material. Through weathering, rock gradually breaks down into smaller particles. Water plays a central role in this transformation. In warm and humid climates, chemical reactions proceed faster, accelerating soil development. But cold climates are not inactive. When water freezes in rock cracks, it expands – much like a glass bottle breaking in a freezer – and slowly splits the rock apart. Over time, even solid rock becomes fragmented.

As soon as microorganisms, plants, and other organisms colonize this material, the process intensifies. Microbes feed on minerals released from weathering and produce substances that enhance further breakdown. Plant roots penetrate cracks and add organic matter as plants grow and decay. Mineral particles and organic residues begin to mix. Gradually, a thin surface layer forms – and, over centuries and millennia, deepens into soil. To better understand why soils differ from place to place, soil science summarizes this complex story into five interacting factors.

© Primary succession diagram by Rcole 17, CC BY-SA 4.0, no changes were made to the original photo

Watch the video “How Soil is Created: The Succession of Life in the Evolution of soil” which was produced by 59degrees. The video illustrates nicely the beginnings of soil formation until minute 4:15. ▶ Watch the video