How is Soil Formed? The Process of Weathering

The Earth's crust is made of giant, solid rocks. Weathering is the extremely slow physical and chemical process of breaking down these massive rocks into tiny grains of sand and dust. This happens through the constant attack of weather forces:

• The Sun (Heat): During the day, the hot sun expands the surface of the rocks. At night, the cold air shrinks them. Expanding and shrinking every single day for thousands of years causes the hard rocks to crack and peel.
• Water and Ice: Rainwater enters the tiny cracks in the rocks. In winter, this water freezes into solid ice. Because ice expands, it acts like a wedge, violently splitting the massive rocks apart.
• Wind and Rivers: Fast-moving rivers roll large stones against each other, grinding them down into smooth pebbles and fine sand. Powerful winds blow sand against mountains, slowly scratching and eroding the rock surface like sandpaper.

A pile of crushed rock dust is NOT soil. If you plant a seed in pure rock dust, it will die.

• To become true, fertile soil, the crushed rock must mix with Humus.
• Humus is the dark, incredibly rich organic material created when dead plants, rotting leaves, dead insects, and animal waste decompose (rot) into the ground.
• Earthworms and microscopic bacteria mix this humus into the rock dust, adding vital nutrients (like nitrogen) and turning it into dark, living soil ready for farming.