One good soil fact for kids is that there are actually different types of soil, including histosols made of organic material, andisols made of volcanic ash, and mollisols found in grasslands. Vertisols are clay soils that are able to swell and shrink a great deal. Oxisols are very weathered soils found in warm climates, while gelisols are soils found in cold climates that contain permafrost within about 6 feet of the surface. Permafrost is not frost, but frozen soil.
Soil consists of horizontal layers that naturally occur as rock breaks down and mixes with organic materials. These layers are called horizons and range from the O horizon, which is the topmost layer, to the R horizon, which is bedrock. The O horizon is made up of fallen leaves and rotted organic matter.
Pedologists – scientists who study soil – rank soil by its texture. Soil can be sandy, silty or clayey. Sandy soil has the largest particles, is not very rich in nutrients, and feels rough to the touch. Silt has the second largest particles and feels soft and powdery to the touch; it is smooth when wet. Clay has the smallest particles, is heavy to hold and is sticky when wet.