The exact number of deserts covered by sand is not specified in the provided reference; however, the reference indicates that only about 20 percent of deserts are covered by sand. This means that the vast majority of the world's arid regions are composed of terrains other than sand.
Understanding Desert Composition Beyond Sand
It is a common misconception that all deserts are synonymous with vast, rolling sand dunes. In reality, deserts are primarily defined by their extreme aridity and low precipitation, not exclusively by their surface material.
- Varied Surfaces: While iconic sandy landscapes (known as ergs) exist, most deserts feature diverse terrains such as rocky plateaus (hamadas), gravel plains (serirs), salt flats, and mountainous regions.
- Precipitation as the Defining Factor: The critical characteristic of a desert is its low annual rainfall. For instance, parts of the Atacama Desert in Chile, one of the driest places on Earth, receive less than two millimeters (0.08 inches) of precipitation per year. This demonstrates that extreme dryness, not sand, is the universal identifier for these environments.
The Proportion of Sandy Deserts
The information provided highlights the relatively small proportion of deserts that are sand-covered:
| Aspect | Description |
|---|---|
| Prevalence of Sand | Only about 20 percent of the world's deserts are actually covered by sand, challenging common perceptions. |
| Dominant Terrains | The remaining 80 percent of desert areas consist largely of exposed bedrock, gravel, stones, or salt pans. |
| Aridity as Classification | Deserts are classified based on their aridity levels, where precipitation is significantly low, rather than their geological surface. |
This underscores that while sand is a notable feature in some of the most famous deserts, it is not representative of all global desert environments.
