Deserts crack primarily because the muddy sediment or clay-bearing soil dries and contracts.
This phenomenon, also known as desiccation cracking, is a common sight in arid and semi-arid environments like deserts, especially in areas where water was previously present, such as dried-up lake beds, riverbeds, or temporary puddles.
How Cracks Form in Desert Soil
The process is quite straightforward:
- Water is Present: Initially, water saturates the soil, particularly types rich in clay or fine mud. This water fills the spaces between soil particles.
- Drying Begins: As the desert sun beats down and wind blows, evaporation occurs rapidly.
- Contraction: Water leaves the soil, causing the fine particles (especially clay minerals) to pull closer together. The soil literally shrinks in volume.
- Stress and Cracking: This contraction creates tension and stress within the soil layer. When the internal stress exceeds the soil's strength, it fails, resulting in the formation of visible cracks. These cracks typically start at the surface and propagate downwards.
The reference explicitly states that mudcracks (also known as mud cracks, desiccation cracks or cracked mud) are sedimentary structures formed as muddy sediment dries and contracts. It also mentions that crack formation also occurs in clay-bearing soils as a result of a reduction in water content.
Key Factors Contributing to Desert Cracking:
- Soil Type: Clay-rich and muddy soils are most prone to cracking due to their structure and ability to hold and then lose significant amounts of water.
- Water Fluctuation: The transition from wet to very dry conditions is crucial. Areas that receive occasional water (from rain, floods, or ancient water bodies) and then undergo prolonged drying are prime locations for cracking.
- Evaporation Rate: Deserts have high temperatures, low humidity, and often strong winds, leading to rapid evaporation and quick drying of the soil.
Visualizing the Process
| Stage | Description | Soil Condition |
|---|---|---|
| Saturation | Water fills pores in muddy/clay soil. | Wet, soft |
| Drying | Water evaporates from the soil surface. | Damp to Dry |
| Contraction | Soil particles pull together as water leaves. | Shrinking Volume |
| Cracking | Stress causes the soil to break into polygons. | Cracked, hard |
Understanding Desiccation Cracks
These cracks often form distinctive polygonal patterns on the surface. The depth and width of the cracks depend on factors like the soil composition, the thickness of the dried layer, and the rate of drying. While common in deserts, this process can occur anywhere muddy or clay soil dries out, such as riverbanks during drought or temporary ponds.
For further reading on sedimentary structures:
The cracking is a natural geological process driven by the simple physics of water loss and material contraction in specific soil types under arid conditions.
