Have you ever asked yourself what soil is made of? Well, it’s made of different types and sizes of solid particles. Some of those are organic while others are minerals. The spaces between the particles can be filled with water or air.


Over time, the soil’s mineral particles begin to change due to weathering. Many things weather rocks, such as hot and cold weather, plant roots, ice, and water. Size is the only thing that changes through this physical weathering process. On the other hand, chemical weathering can change minerals or rocks into other minerals or rocks. They become something completely different. Here is one way to think about it: Take a cookie and break it in two. Each piece is still the same cookie but smaller. You can break it over and over again, and it’s still the cookie. That is just like physical weathering. Put the cookie in your mouth, though, and the saliva begins to mix with the cookie. This will begin the process of digestion. Once this happens, the cookie is no longer a cookie. You couldn’t put it back together again. This is like chemical weathering.

Another part of the soil is humus. Organic particles in the soil make up humus. The organic particles are decomposed parts of animals, plants, and microorganisms. The soil “eats” the organic tissues from the plants and animals. The soil gets energy from these and then will create waste. Humus is the waste product that is produced from the soil.

thumb-ebf72f9951b04c5d05330f906135c161The particles in the soil are separated by their size. If a particle is over two millimeters, it is gravel. If it is between 2 and 0.05 millimeters, it is considered sand. Silts are between 0.05 and 0.002 millimeters. If the particles are under 0.002 millimeters, they are clay. The ratio of mixture of these particles determines the texture of the soil. Clumps (peds) are formed when the individual particles are held together by humus. The soil structure is determined by the size and shape of the peds.

As you can see, air, water, organic solids, and minerals make up soil. The properties of the soil are affected by the microorganisms, animals, and plants that live in the soil.