Understanding Earth & Soil

Experiencing nature gives us immense joy & pleasure. Be it in walking along a park trail lined by lush green trees, seeing vast green spaces or perhaps even seeing puddles and little streams after a rain shower. We love the sound of the humming birds, enjoy the weather and the fresh cool breeze. We love the sight of bright flowers all around and the squirrels crossing our path.

Does anyone spare a moment to think about the earth under their feet?

The world continues to move from the stone age to the space age because the principles of physics remain the same. It is only as we understand them better and experiment do we make advancements that benefit our lives.

We know more about the Sun, Moon and other planets in space but hardly know our Earth. Ever wondered how we can accurately predict solar and lunar eclipses but are caught off guard by disastrous flash floods, earth quakes, tsunamis and landslides?

The earth underneath us is so diverse and alive that the more one thinks about it, the more magical and mysterious it appears. It is the place where at each moment every law of physics is in action and which is holding within it the entire periodic table, innumerable organic and inorganic compounds and minerals and air and water and the living and the decomposing.

The core of the earth is about 6300 Km. from where we stand but humans have not been able to drill below 12 km (see ref). Most people do not even know that the ground well below our feet is may be hotter than the surface of the sun.

The layers of earth based on chemical variations from shallowest to deepest are:-

1. Crust: Earth’s crust is the outermost layer of earth and ranges from 5–70 kilometers in depth.
2. Mantle: Mantle lies between Earth’s crust and dense super-heated inner core and is about 2,900 km. thick.
3. Outer Core: Earth’s Outer Core is largely liquid iron layer of the earth that lies below the mantle. The outer core is about 2,300 km. thick.
4. Inner Core: Earth’s inner core is the innermost geologic layer of the Earth. It is primarily a solid ball with a radius of about 1,220 km. The inner core is believed to be composed of an iron–nickel alloy with some other elements.

Our aim here is to give some insight to our readers that our earth is magical and that the earth’s resources are major components which impact the environmental factors which make planet earth habitable.

We do not wish to wade into a theoretical discussion about permeability or porosity of soil or about range of validity of Darcy’s law or velocity of flow of water. We would restrict our discussion to shallow depth of the earth’s crust since no man has ever explored the other layers in person – in fact at a maximum depth of 12kms, our civilization has barely scratched the surface.

The most common components with varying percent found in composition of the soil.

Capacity	Sand	Clay	Silt
Aeration	Good	Poor	Medium
Water-Holding	Low	High	Medium
Compact-ability	Low	High	Medium
Drainage	High	Slow	Medium
Leakage-prevention	Poor	Good	Poor
Result of tilling after rainfall	Good	Poor	Medium
Erosion by water	Medium	Low	High
Erosion by air	Medium	Low	High
Capacity to hold plat nutrients	Poor	High	Medium
Capacity to shrink or swell	Low	High	Low
Decomposition of organic matter	Fast	Small	Medium

Sand has pockets which hold air hence aeration is good and the voids are interconnected hence water holding capacity is low and drainage rate is high. This causes the compact-ability to be low and its use as a sealer to prevent leakage is not advisable.

This is the reason why it is beneficial to till the sandy land after rainfall. Planting of trees and bushes and construction of check dams are recommended to prevent soil erosion by air and water.

Some form of clay when added to sandy soil, enhances the cultivation output because it reduces soil erosion both by air and water and increases the compact-ability, water retention capacity & plant nutrient holding capacity of the soil.

If we explore the properties of soil we come across a list which is unending.

• Soil not only serves as an anchor but also provides the required minerals and water to the plants. In fact this resource provides 99% of the food consumed by human beings.
• Soil is a major raw material required for manufacture of many types of building materials. Soil is the foundation of construction projects.
• Soil absorbs and cleans rainwater as it percolates through it and also holds it in the aquifers. This quality of soil not only serves as a source of ground water when needed but also protects us from floods and in time of droughts.

Interestingly, it has been observed that many animals deliberately ingest soil as it absorbs toxins, and facilitates digestion and checks diarrhea and it is also a source of rare minerals. The practice of eating soil is referred as Geophagy

Soil protection and conservation is very important since soil is the home for many organisms living in such interconnected harmonious diversity both inside and outside the soil like earthworms, snails, slugs, millipedes, centipedes, potworms, nematodes, bacteria, fungi and algae, to name a few. Aerobic processes of soil have a major role to play in waste management while handling effluent from septic tanks and elsewhere.

It is estimated that soil restoration will offset the effect of increases in greenhouse gas emissions and slow global warming. About 60% of the biotic content is carbon and this makes the Biological component of soil is very important. Even in desert crust, cyanobacteria which are microorganisms related to the bacteria but capable of photosynthesis, lichens and mosses capture and hold a good quantity of carbon by photosynthesis.

When we talk about water conservation, it is intricately tied to soil conservation as well. Preventing the erosion of soil through water conservation, rain water harvesting, green-belt development, responsible agricultural and industrial practices therefore has many inter-linked benefits – from improved soil quality to reducing the effects of global warming.