Reasons:
* Composition: Sandstone is composed of sand grains cemented together, while granite is a much harder igneous rock composed of quartz, feldspar, and mica.
* Porosity: Sandstone has a higher porosity than granite, meaning it has more spaces between the grains. This allows water to infiltrate and penetrate deeper, leading to more erosion.
* Cementation: The cement holding the sand grains together in sandstone can be weaker than the minerals in granite, making it more susceptible to weathering and erosion.
* Hardness: Granite is a much harder rock than sandstone, making it more resistant to abrasion and erosion.
Conclusion:
The porous and less cemented nature of sandstone makes it more vulnerable to the erosive effects of rain compared to the denser and harder granite.
