Soil Horizons

Soil Horizon

My husband just introduced me to a great book called, “Dirt- the Ecstatic Skin of the Earth” by William Bryant Logan. He wrote a great chapter about the beauty of “soil horizons”. If you’re ever driving down a fresh road cut or beside a beach you may see the “soil’s body exposed” in distinct, dense layers of color like a sunset. Apparently rainwater, which is made more acidic and chemically active by picking up CO2 in the air, drips down through the soil and chemically extracts and moves aluminum, silica, clays, humus and mostly iron down through the layers. It makes the subsoil layers shades of red and the top silica turns white. In a great soil horizon you might see a red and orange subsoil teeming with life with streaks of green and purple lichen and turquoise mosses growing through channels. He says that the unbelievable beauty of soil horizons is often what makes people want to become soil scientists. To describe all of these different types of soils and soil horizons, they’ve come up with ten soil orders, fourteen thousand soils with proper names (like haplahumod and quartzipsamment) and 21 letter designations to distinguish different characteristics of soil horizons! Keep an eye out when you see road work ahead!