soil: the nexus
the "solid ground" we walk on is only about 50% solid — made mostly of minerals and 1-10% organic matter. the remaining 50% is open, pore space — filled with either air or water.
ecosystem services
soils are the foundation of nearly every ecosystem on the planet, providing important services that give rise to healthy plants, healthy people, and a healthy planet!
"essentially, all life depends upon the soil... there can be no life without soil and no soil without life; they have evolved together." -charles kellogg
soil formation
rock weathering
through a combination of physical, biological, and chemical processes, rocks break down into smaller and smaller pieces.
parent material
sources
- rocks either weather in place or are deposited in one of the following ways:
types
- rocks are composed of different types of minerals that weather at different rates
soil forming factors
as energy flows through the system (heat, precipitation, etc.), particles continue to weather and soils develop horizons and other distinct morphological features. the formation of soil over time is called pedogenesis.
the finer the particles, the faster the weathering, but mineralogy matters! silica is one of the least weatherable minerals, while minerals high in iron and magnesium weather more readily.
soil processes
rain/flooding, dust, animal
and plant residues, fertilizers
erosion/runoff, leaching,
metabolism, volatilization
gravity/water, evaporation of
salts, mixing by organisms
decomposition of residues,
weathering of rocks to clay, iron oxidation