The soil from what we found out was so incredibly hard and compact has a unique in interesting past. Through the history of New Mexico, the soil has been modified by erosion, which has helped with the addition of new minerals, compaction, and overall has changed the composition of the soil in its entirety. This has created a soil that is incredibly hard, fine, and that is semi permeable. But why is it that this soil is this way?
Generally speaking, much of the southwest region of the United States and in deserts all around the world have this CaCO3 surplus in it’s soils. The CaCO3 is commonly referred to as caliche, and is what is responsible for making the ground so hard and so much like concrete. In New Mexico, it comes from decomposed marine life (since New Mexico used to be a large ocean bed), and thus all of the old and decomposed oceanic life are. This creates lime scale, which is why (for any New Mexico resident) you will see green “moss” around taps if they are used for long enough. This is also why normally pumped sometimes will taste a bit salty. All of this happens because of New Mexico’s past. However, that still does not answer the question of how it makes soil so hard.
The classification of CaCO3 is that it is indeed a salt. Salts are easily dissolved in water, and are highly reactive when soluble. This means that water can rush down and can permeate the ground while carrying large amounts of calcium carbonate. While soluble, the caliche is able to form compounds such as calcium silicate, and calcium aluminate, which are both similar to cement like compounds. When added to the already very close to clay like soil that we have, the particles are drawn closer together by these bonds, and they are both drawn very close together, and are held together by these bonds. However, this is easily counteracted by the addition of water, as Calcium is easily dissolved with water, and thus the bonds are easily broken, and the soil returns to a state in which it seems to not be quite so cement like and is much easier to dig in general. Sadly, New Mexico’s climate does not receive significant enough rain to disperse this salt, so when digging it is advised that the area is thoroughly soaked before hand. This caliche is truly the enemy of digging, but it is utilized in the world around us today.
It should be no surprise to anyone that calcium carbonate is used in cement. It is used in much of the same way, as it forms bonds, this time with aluminum silicone, and sulfur to form calcium aluminosilicate and calcium sulfate. These bonds are not only incredibly hard and strong, they are also waterproof. Recently for an art class we used a cement like substance called mortar to help hang ceramic birds we made on archways around school. We learned that it is used to hold tiles in place, and is used in almost every building. Well, limestone (which is Calcium Carbonate) is one of the key ingredients within this, and it creates these incredibly strong bonds when activated by water that make it so hard and useful in the modern world. It is also used environmentally to help cancel out acidic lakes and rivers, and is used by farmers as a key nutrient in the growing season. Overall though, the benefits seem to outweigh the consequences, as clearly New Mexico’s agriculture has thrived from the soil and from this calcium carbonate which is able to provide nutrients to the plants without raising the pH to a point where the plants will never be able to thrive. It is a key element within the soil that is what makes New Mexico and deserts around the world unique and so special in terms of the soil they possess.
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