How is soil formed?

How is soil formed

Soil is a mixture of minerals, organisms, gases, air, and water decaying to form earth’s land surface. It’s a critical component of every ecosystem. But how is soil formed?

How is soil formed? Soil Formation Basics  

When rocks are exposed to the elements, they begin to transform into soil. This process can take anywhere from 500 to thousands of years and happens through five factors. These factors are most easily identified as CLORPT: Climate, Organisms, Relief, Parental Material, and Time.  



  • Cl – Climate: Exposure to physical weathering such as freezing and thawing in colder climates, chemical weathering in warmer climates, and precipitation the rock cracks and develops fissures.
  • O – Organisms: Plant roots, burrowing animals, and enzymes such as bacteria and fungi break down the rock and alter its physical content. 
  • R – Relief: Topography or slope of the landscape influences how much direct sunlight a rock receives, temperature, water runoff, organic material build-up, and erosion rates.
  • P – Parental Material: Underlying bedrock which influences the chemical composition of soil formation in any given area.
  • T – Time: Weathering time which breaks down the rock until it is no longer recognized as rock.

These five factors work together in the soil formation process. This is how it works:

When rock is exposed to climate factors such as heat, freezing, thawing, rain, window, and other atmospheric pressures it breaks down into small fragments which becomes the parent material of the soil.

In these small fragments, living organisms alter the rock’s biological and chemical make-up which begins the weathering process.

Over time, organisms encourage the growth of microorganisms as well as plant and animal populations. The growth of these creatures provide key nutrients for the continual formation of soils and further plant life.

What is soil made of?

CLORPT and Soil Composition

We’ve determined that soil is a formation of five key ingredients – minerals, living organisms, gas, organic matter, and water. These factors also determine the soil’s class.

Soil is divided into three classes: clay, silt, and sand. Within each class, there are different compositions of soil which constitute a soil’s texture.

Every region’s soil texture differs due to CLORPT. These five factors all work together to give each soil its own distinct characteristics. Here’s how:

Climate alters the amount of nutrients and minerals in a given area’s soil. The weathering process is responsible for the speed at which nutrients are deposited into the soil and microbes decompose into organic material. A region’s climate also influences the amount of oxygen in soil, which can either help microbes flourish or die off.

Organisms in different regions affect the soil formation process. For example, prairies or grasslands vegetation have higher nutrients than forested areas since grass life vegetation is constantly dying off and provides the soil with key microorganisms.  Whereas, low plant life turnover rates in forested areas leads to less nutritiously dense soils.

Parental material affects the composition of organic materials present in soil. So for instance, if soil is located near volcanoes, it tends to be richer in overall minerals due to the erosion of volcanic ash.

Relief affects the layers of composting materials in a given soil.

And Time allows a soil formation to be either “young” or “old.”  Soil is considered old if it has not been disrupted for a long period of time. Whereas, it is considered young if it was abruptly moved via a volcano, landslide, or glacial retreat.

How Compost Can Benefit Soil

Soil is a critical component to the earth’s surface that plays different roles in our ecosystem:

  • hosting plant, animal, bacteria, and fungi life
  • modifying our atmosphere by absorbing and emitting gases
  • absorbing, emitting, and purifying water before it moves to an aquifer
  • recycling nutrients such as carbon.

As not all soil is created equally, there are benefits of adding compost to local soils. Compost helps add macro and micronutrients to soils. It also slowly releases key nutrients into soils over months or years. Compost can also help complement existing soil structures.

Add compost to soil

  • Compost helps nutrients remain tightly bound to prevent them from washing away.
  • Compost makes soil less likely to erode.
  • Compost tightens the bound particles such as clay or silt to water can properly drain.
  • Compost helps sandy soil retain key nutrients and water.

To better understand why composted materials are beneficial for soils, it is important to understand the nature of compost decomposition. This natural process returns organic matter and nutrients to the soil.

How Compost Decomposition Happens

Soil formation and compost decomposition have several similarities. Bacterial, fungi and living organisms are essential components to both processes. 

In both processes, bacterial and fungi growth allows for the breakdown of organisms to form either soil or compost. While soil formation is the breakage of rocks, composting is the breakdown of organic material such as leaves and food waste into a soil-like state.

There are three main stages of compost decomposition, each of which is dominated by a group of microorganisms that thrive in different temperatures.

  • The mesophilic (moderate temperature) phase, which lasts up to a few days.
  • The thermophilic (high temperature) phase, which lasts from a few days to several months.
  • The cooling phase, which lasts for several months.

In the mesophilic phase, temperatures range from 68-114F (20-45C), and microorganisms rapidly break down soluble, readily degradable compounds. This process produces heat which causes compost temperatures to rise above 104F (40C), giving way to the thermophilic phase.

In the thermophilic phase, thermophilic (“heat-loving”) microorganisms further break down organic materials into finer particles. Higher temperatures are favorable to break down proteins, complex carbohydrates, and fats (the major building blocks of plants). This phase can last up to several months.

Once thermophilic microorganisms break down the entire supply of complex compounds in the compost pile, the temperature begins to drop again. The cooling phase begins with the return of mesophilic microorganisms that finish breaking down the last bits of organic matter. 

PRO TIP: Thermophilic temperatures kill off most microorganisms as well as human and plant pathogens. Because there are fewer organisms working in the pile compared to the mesophilic stage, decomposition slows substantially.

This is one reason why consistently turning a compost pile is so important. Turning your pile cools it down and introduces oxygen, which is one element that all aerobic (oxygen loving) microorganisms need. 

Leave a Comment

Your email address will not be published. Required fields are marked *