CHALLENGE

Start

Theories so far Terrestrialisation Tools

Making Soil

There was no soil half a billion years ago. Soil has developed in the last tenth of the age of this planet. Nowadays, estimates of the total amount of soil on Earth can vary, but it is generally accepted that there are around 1.5 trillion tons of soil on the planet. Our challenge is work out how 3000 tons a year of soil have been made each year for the last 1/2 billion years.

This story of soil of how soil was made is a new way of looking at the world, from underground.

Total soil = 150,000,000,000 lorry loads (each 10tons)

We are going to use old-fashioned detective work, along with state of the art science, that can see beyond the human eye, to get to the truth. We will unearth truths, time and time again over hundreds of millions of years, leaving no stone unturned. There will be red herrings, twists and turns, and blind alleys, but it wouldn't be much of a story if it didn't have these.

Soil, the world over, have similar functions, yet each patch is different. When you hear about soil 'formation' or 'pedogenesis', you will hear about the factors that make it, like substrate, climate, drainage and organic types, over thousands of years. However, here we are going back much earlier - millions of years, to find out how those factors came into being, in order to form soils today. It is not just the organisms which evolved over long periods of times, but also the processes, like decomposition.

Conquering or Constructing?

The way creatures and plants changed the land beyond the sea is one of the great evolutionary stories. However, it is often summed up with a word like 'terrestrialisation', a sort of scientific magic process. You may read: 'Plants and creatures ‘conquered the land’, conjuring an image of an invasion of organisms stomping over the land. They couldn't move far, as they would soon dry out and die. Instead, we should look at how they ‘constructed the earth by various minerals, plants, organisms, and creatures making underground structures. Here, our challenge is how that could have happened.

Weathering

'Weathering' wears down the rocks.

Physical weathering is where wind and water erode the rocks and changes in temperature can crack them into particles, the size of boulders, sand and clay.

Chemical weathering is the breakdown of minerals in rocks due to exposure to atmospheric agents, such as water, oxygen, and acids. Water plays a key role. Common chemical weathering processes include hydrolysis, oxidation, and carbonation.

Very small clay particles, called feldspar (known as the 'mother of clay') weather by hydrolysis.

Hydrolysis, involves the reaction of minerals with water, leading to their breakdown into clay minerals and dissolved ions.

As well as feldspars, most rock-forming aluminosilicate minerals will weather to form soil clays because soil clays are more thermodynamically and kinetically stable under surface conditions.

There is also Bioweathering

Many people think that ‘weathering’ makes soil. But it does not. It may break down rock, but that produces mud, silt and mud. Not soil. There is no soil structure.A rock will generally undergo chemical weathering faster buried in soil than it will exposed to the open air. However, this depends upon the type of chemical weathering, as oxidation may be more efficient in the open air in humid conditions than in an anoxic (with little air) soil horizon.

In the 19th century many soil scientist soil was formed by weathering. But on its own it does not make soil. The end result of weathering is not soil. It is sand, silt, clay and minerals. All these are vital ingredients and components for soils. Their physical and chemical properties can determine the nature of soils, but in themselves they are not soil.

Rainwater

Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it. Carbon dioxide (CO2) mixes with water (H2O) to make carbonic acid (H2CO3), which persists as its salts - carbonates. Minerals, in rocks may react with the rainwater, causing the rock to be weathered

The most common minerals that undergo weathering in the presence of rainwater include:

Feldspar: This is a group of minerals that are commonly found in many types of rocks, such as granite. Feldspar weathers to form clay minerals and dissolved ions like potassium, silica, and aluminium.
Calcite: This mineral is a major component of limestone and marble. It reacts with acidic rainwater, which contains carbonic acid, to form dissolved calcium ions, bicarbonate ions, and carbon dioxide.
Biotite and Muscovite Mica: These are common minerals found in many igneous and metamorphic rocks. They weather to form clay minerals.
Pyroxenes and Amphiboles: These are common minerals in mafic (rich in magnesium and iron) rocks like basalt. They weather to form clay minerals and dissolved ions.
Olivine: Found in ultramafic rocks, olivine weathers to form serpentine minerals.

Lichens

Lichens are symbiotic organisms composed of a fungus and a photosynthetic partner, usually green algae or cyanobacteria. The relationship between the fungus and the algae is mutually beneficial. The chemicals produced by the fungus play a crucial role in enhancing the survival and growth of the algae within the lichen structure. The mutualistic relationship works by:

Mineral Breakdown: The fungi in lichens can produce chemicals, such as organic acids, that have the ability to break down minerals present in the substrate, which is often a rock or soil. These chemicals help dissolve minerals like calcium, magnesium, and potassium.
Nutrient Release: As the fungus breaks down minerals, it releases nutrients in a form that is more accessible to both the fungus and the algae. The algae, being a photosynthetic organism, can utilize these released nutrients for growth and metabolism.
Enhanced Nutrient Uptake: The breakdown of minerals by the fungus not only releases nutrients but also creates a more favorable environment for nutrient uptake by the algae. The organic acids produced by the fungus can increase the availability of essential nutrients for the algae, promoting their growth.
Protection: The lichen structure provides a protective environment for the algae, shielding them from harsh environmental conditions such as extreme temperatures, UV radiation, and desiccation. The fungus contributes to the formation of a structure that helps retain water, creating a microhabitat suitable for algae survival.
Stability and Structure: The fungal partner provides structural support for the lichen, creating a stable environment for the algae to thrive. This symbiotic relationship allows the algae to colonize a variety of substrates, including rocks, trees, and soil.

Structure

Weathering has gone on for hundreds of millions of years. But that alone does not make soil. Soil has structure.

The key characteristic of soil is its structure - based on 'lumps' of soil called 'peds'.These lumps consist of a wide variety of minerals, particles, and organic matter making the soil strong and stable and an environment to live in. (More on Peds and pores)

Peds

Lumps

The first signs of soil are when fungi, bacteria, and soil animals start feeding on debris, and the resultant compounds would stay on the surface, rather than being washed straight away. Biological 'lumps' of material are less likely to be washed away, but become bound beneath vegetation We see after heavy rain how rivers become opaque with particles derived from soils. If the soil is 'healthier', and more structured, less is lost. (Throughout this soil evolution story, we use what we see today to try and imagine what went on millions of years ago.)

How did occasional lumps become trillions and trillions of 'peds' throughout the world that make our soil so stable?

Peds

‘Peds’ are structures consisting of mixtures minerals and organic matter stuck together that give soils their strength and resilience Peds are aggregates of an infinite variety of substances that suck together. They are mixtures of different organic and inorganic materials bound together with various sticky compounds. They are strong resilient, flexible and create the atmosphere for life to go on beneath ground. There are all sorts of soil types, properly classified. Minerals alone lack the key component of soils that gives soil science its name - pedology.

Mollisol or Chocolate cake

Entisol or Angel Food Cake

Cake

The end result could be an omelette, a souffle, pancake, a loaf of bread, an ice cream, or a cake.like these here, with their corresponding soil.

Each of these have ways of making air stay still. Both soils and cakes have cavities and passages supported by structures that give a little and take a little.

Gelisol or Ice Cream Cake

Alfisol or Carrot Cake

That’s not forgetting the drinks like beer, whisky, wine or cider, each of which have biological processes which thrive in liquid conditions to make many flavours. Put all these together and you begin to taste and smell the richness of soils.

Soil as Cakes

Entisols: Angel Food Cake
- Entisols are young soils with minimal horizon development. Angel Food Cake is light and fluffy with a simple structure, much like the minimal development in Entisols.
Gelisols: Ice Cream Cake
- Gelisols are soils that contain permafrost within two meters of the surface. Ice Cream Cake can be seen as a cold and frozen type, making it a fitting analogy for Gelisols.
Alfisols: Carrot Cake
- Alfisols are moderately weathered soils with a good nutrient content. Carrot Cake, with its mix of flavors and nutrients from carrots and other ingredients, aligns with the characteristics of Alfisols.
Mollisols: Chocolate Cake
- Mollisols are fertile soils with a dark, rich layer that is characteristic of high organic matter content. Chocolate Cake, being deliciously dark and rich, can represent the fertility and organic matter of Mollisols.

Thank you ChatBPT [do you mean ChatGPT?] for this, which added "Remember, this is just a playful analogy, and the actual characteristics and classifications of soils are much more complex and scientific."

Horizons

The photographs above are the result of pedogenetic processes on one particular soil. You will observe several layers perly called horizons.,The various horizons get their colours from different processes at work, like a black horizon gets its colour by being rich in organic material. A white-ish horizon isi usually due to minerals leached out of it by chemical weathering, and a pinkish horizon takes its colour from the iron oxides that have been deposited in it by the rainwater seeping through the soil. A crucial function of soils is that they recycle the minerals rather than them being waste and going out into the oceans.

But how did these well-layered soils get here? You will hear that these 'types' of soils would take thousands of years to make. But they are working from existing materials and processes. Where did they come from? We have to look back millions of years., as they arrive at different times.

To make sense of the running order of what came when we will look in detail at what creatures and plants would have been around in the various periods. To help with working out these dates we will use various existing tools in paleobiology.

Tools

While exploring soil evolution, we shall use scientific tools for morphological and molecular evidence, and now AI photography. If we are still not sure, we will view the events as if we were in that 'environment' all those years ago to try to work out what happened. This is what Ghilarov recommended over 50 years ago. We will also look at what we can see today to try and understand what went on all those years ago. For more on tools

Real Challenge

The real challenge is for people to start seeing soil, this massive mass of life, as a dynamic entity not a static lump of dirt. That applies to scientists too. While it now lives as a whole all working together, all the parts arrived somehow at some point. I will make suggestions as to how.

They will all be possible, but I would also like them to be plausible too, but it will be a long time before they are provable. There is much debate to be had from this new perspective. And some suggestions - as there are so many - will be wrong. You can be a scientific sleuth evaluating the evidence. I hope you and others take into account the environmental changes occurring at the time. That way we should be able to make a lot more sense of the extensive findings we have already dug up with the tools of the trade.

The start of the challenge is the way we see soil

That directs the science for soil

Which uses these tools

Page updated

Google Sites

Report abuse