Types of Soil Erosion: Geological and Accelerated

Soil is the foundation of all agriculture – and it’s disappearing faster than most people realize. According to the FAO, it can take up to 1,000 years to produce just 2-3 cm of topsoil, yet the equivalent of one soccer pitch of soil is lost every five seconds globally. To understand why this is happening – and how to stop it – we first need to distinguish between the two fundamental types of soil erosion: geological erosion and accelerated erosion. These two categories differ dramatically in cause, rate, and consequence.

What is soil erosion? 🔗

At its core, soil erosion is the detachment and transport of soil material from one location to another by agents such as water, wind, ice, and gravity. Soil erosion is a form of soil degradation that can proceed slowly and unnoticed, or surge to alarming rates that strip farmlands of their most productive layer – the topsoil. Once topsoil is lost, the remaining soil is typically less fertile, more compact, and less capable of retaining moisture and nutrients – making crop production significantly harder.

Geological erosion: nature’s slow sculptor 🔗

Geological erosion, also called natural or normal erosion, is the wearing away of land by natural forces – water, wind, ice, and gravity – without any meaningful human interference. It is an inherently slow process that has been shaping the earth’s surface since its formation.

How geological erosion works 🔗

The main agents of geological erosion are straightforward. Rainfall and rivers break down rock surfaces and transport sediment downstream. Glaciers and ice sheets grind against rock, carrying enormous quantities of material. Wind scours dry surfaces, relocating fine particles over vast distances. Together, these forces have carved out river valleys, shaped coastlines, and built fertile plains over millions of years. Geological erosion is, in fact, responsible for forming the fertile plains that underpin much of the world’s agricultural land today.

The rate and balance of geological erosion 🔗

The key characteristic of geological erosion is its pace. In natural ecosystems, geological erosion typically occurs at a rate slower than the rate of soil formation – because the soil remains protected by vegetation. Aboveground plant cover reduces wind speed, while root systems anchor soil particles in place. This natural balance means that, over geological time, soils can form, stabilize, and support ecosystems without being depleted. The process is so gradual that it often goes completely unnoticed within a human lifespan.

Geological erosion as a constructive process 🔗

It is important to note that geological erosion is not inherently destructive. It contributes to soil formation – by weathering parent rocks into mineral particles – and to the distribution of soils across landscapes. Topographical features such as stream channels, river deltas, and valley floors are all products of long-term geological erosion. For ecosystems, this is a background process that supports rather than undermines land health.

Accelerated erosion: when human activity tips the balance 🔗

Accelerated erosion occurs when the rate of soil loss significantly exceeds the rate of soil formation – driven primarily by human activities that disturb or remove the natural protective cover of vegetation. This is where erosion transforms from a background natural process into a serious environmental and agricultural crisis.

Primary causes of accelerated erosion 🔗

The human activities most responsible for accelerated erosion include deforestation, intensive agriculture, overgrazing, and urbanization. When forests are cleared, tree roots no longer hold soil in place, and the canopy no longer intercepts rainfall. In agricultural settings, intensive tillage breaks up soil aggregates, leaving bare soil exposed to raindrop impact and surface runoff. Overgrazing strips vegetative cover and compacts the soil, reducing its capacity to absorb water. According to the FAO, unsustainable human activities can increase soil erosion rates by up to 1,000 times compared to natural levels.

Research published in the Proceedings of the National Academy of Sciences confirms that conventional plow-based agriculture increases erosion rates by one to two orders of magnitude compared to geological baselines – rates high enough to erode through a typical hillside soil profile within the lifespan of a civilization. In contrast, no-till agriculture produces erosion rates far closer to natural soil production rates.

Forms of accelerated erosion 🔗

Accelerated erosion manifests through several recognizable forms, most of which are driven by water and wind acting on disturbed soil:

Splash erosion is the first and least severe stage. When a raindrop strikes bare soil, it dislodges soil particles, ejecting them up to 50-75 cm vertically and 1.5 m horizontally. The impact breaks up soil aggregates, setting the stage for further erosion by surface runoff.

Sheet erosion follows splash erosion. It involves the more-or-less uniform removal of a thin surface layer of soil across a slope by flowing water. Because it happens gradually and uniformly, sheet erosion is often the hardest to detect visually – yet it silently strips away the most fertile topsoil.

Rill erosion occurs when surface runoff concentrates into small channels or rills on a slope. These small channels act as both sediment sources and sediment delivery pathways. Rill erosion intensifies wherever water erosion rates on disturbed land are highest, and is a clear sign that sheet erosion has progressed.

Gully erosion is the most severe form of water erosion. When rills go unchecked, they widen and deepen into gullies – large channels that cut through the landscape, making the affected land nearly impossible to till or reclaim. Gully formation is a strong indicator of advanced land degradation.

Stream bank erosion involves the removal of soil from the banks of streams and rivers, aggravated further by vegetation removal, overgrazing, or cultivation near water bodies. During floods, saturated banks can collapse under the pressure of receding water, accelerating the loss of riparian land.

Wind erosion becomes a significant factor in arid and semi-arid zones where vegetation cover is sparse. Moving wind detaches and transports fine soil particles – sometimes thousands of kilometres – through processes of surface creep, saltation, and suspension. The Dust Bowl of the 1930s in the United States remains the most iconic example of wind-driven accelerated erosion at a catastrophic scale.

Geological vs. accelerated erosion: key differences 🔗

The distinction between these two types is not just academic – it has direct implications for land management and conservation policy.

Cause: Geological erosion is driven purely by natural forces; accelerated erosion is primarily caused by human disruption of land cover and soil structure.

Rate: Geological erosion operates over millennia and stays broadly in balance with soil formation. Accelerated erosion outpaces soil formation dramatically. While geological erosion accounts for roughly 30% of total sediment production in the United States, human-driven accelerated erosion accounts for the remaining 70%.

Impact on soil health: Geological erosion contributes to soil development and landscape formation. Accelerated erosion degrades soil quality by stripping away the nutrient-rich topsoil, reducing organic matter content, and diminishing the soil’s capacity to hold water.

Reversibility: Geological erosion’s effects unfold over geological time and are part of natural cycles. The losses from accelerated erosion, however, are not recoverable within a human lifespan – soil is a finite resource.

Why accelerated erosion is a global crisis 🔗

The consequences of accelerated erosion reach far beyond individual farms. The FAO identifies soil erosion and land degradation as a major threat to global food security, affecting the well-being of at least 3.2 billion people worldwide. Since 95% of the food we consume comes from the soil, the stakes are enormous.

On the farm, soil erosion can reduce crop yields by up to 50% by depleting the nutrients and rooting space available to plants. Crops that do manage to grow are often smaller, misshapen, and less nutritious. Off the farm, eroded sediment clogs waterways, degrades water quality, accelerates flooding, and damages infrastructure. Every year, approximately 12 million hectares of land are lost globally – land that could otherwise support food production.

If current trends continue, over 90% of the Earth’s soils could be degraded by 2050 – a timeline that should concern every farmer, policymaker, and citizen.

Controlling accelerated erosion: practical approaches 🔗

The good news is that accelerated erosion is largely preventable through sound land management. Keeping the soil covered – either with growing plants or crop residues – remains the most effective strategy, as vegetation absorbs raindrop energy and slows surface runoff. Conservation tillage and no-till systems significantly reduce soil disturbance and exposure. Cover crops protect the soil between main crop cycles. Contour farming and terracing slow the flow of water down slopes, reducing its erosive energy. Riparian buffers – strips of vegetation alongside streams – help stabilize banks and filter sediment-laden runoff before it reaches waterways. The FAO recommends integrating these sustainable soil management practices into both farm-level decisions and national land use policies to effectively reduce erosion at scale.

What do you think? Given that accelerated erosion is largely driven by farming and land-use decisions, how much responsibility do individual farmers bear in combating it – and how much should fall on national agricultural policy? And with soil formation taking up to 1,000 years, do current conservation efforts move fast enough to protect the soils future generations will depend on?

References

1. https://www.fao.org/about/meetings/soil-erosion-symposium/key-messages/en/
2. https://en.wikipedia.org/wiki/Soil_erosion
3. https://www.researchgate.net/post/What_is_the_exact_difference_between_geological_erosion_and_accelerated_erosion_and_which_kind_of_erosion_is_dangerous_for_soils
4. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/accelerated-erosion
5. https://www.pnas.org/doi/10.1073/pnas.0611508104
6. https://www.soils4teachers.org/erosion
7. https://www.fao.org/newsroom/story/Let-s-StopSoilErosion-to-ensure-a-food-secure-future/en
8. https://www.undrr.org/understanding-disaster-risk/terminology/hips/en0019
9. https://www.fao.org/global-soil-partnership/areas-of-work/soil-erosion/en/