Introduction
A majority of soil is made up of air and worms travelling through soil improve drainage and aeration, which promotes plant growth. (Photo Credit: Chris Thomas / IUPUI Earth Sciences)
Some people are connoisseurs of wine. Others are connoisseurs of chocolate. Earthworms are connoisseurs of soil: they spend their whole life eating and excreting dirt. If anyone understands the diversity and complexity of soil, it’s an earthworm. To your average earthworm, the difference between eating the soil at White River State Park and Fort Harrison State Park is like the difference between eating at Pizza Hut and White Castle.
So what makes soils so different? Here in Central Indiana, some of you may be familiar with our heavy clayey soils. However, if you lived in Western Nebraska, you would have very sandy soil, and if you lived in Oklahoma, you would have red silty soils.
Soils are amazingly complex! They represent how all of our major Earth spheres interact. As we just learned in the Rocks and Minerals module, soils are made up of sediments. But that’s not all. Soil also has bits of organic material from plants and animals, as well as, water and air. This means that we could not have soil without the interaction of the Hydrosphere, Atmosphere, and Biosphere with the Lithosphere. With each part of the world having its own unique climate, plant, animal life, and tectonic setting, soils differ around the world. Soil scientists even have a means to classify soils using soil taxonomy. Just like biologist classifies plants and animals by Kingdom, Phylum, Class, Order, Family, Genus, and Species, soil scientists classify soils into Orders, Suborders, Great Groups, Subgroups, Families, and Series, a soil series being the equivalent of an animal species.
And just like states all have a state flower or bird, so does each state have their own state soil series! Indiana’s state soil series is Miami. These soils are formed from carbonate minerals from the Wisconsin Glaciation – remember from our last module that Indiana was once covered in glaciers. These soils are also formed in wet hardwood forests – up until the mid-1800s, Indiana was mostly a wetland forest. These soils are highly productive and Indiana’s nearly 800,000 acres of Miami soils are the reason why we have such a successful agricultural based economy!
So how do these soils develop and how do we get different soil orders, families, and even series? Well, we’re about to find out. In this Module we’re going to learn how we get soil from sediments (one of the stocks in the Rock Cycle) and how the mineral properties of soils determine the uses for soils. Keep in mind that soil is an essential resource for humans. We either need them to build shelter, or we need them to grow food. We’ll learn later that we even use soils to dispose of our waste. And we don’t necessarily want to dispose of waste in the same type of soil we grow our food – at least not next to each other!