The Permeability of Different Types of Rocks
Which type of rock is the most permeable based on its hydraulic conductivity?
a) Limestone in a karst region
b) Sandstone
c) Fractured granite
d) Unfractured gneiss
e) Mudstone
Answer:
The correct order of rock types by likely permeability, from most to least, is limestone in a karst region, fractured granite, sandstone, unfractured gneiss, mudstone which corresponds to option (a).
Explanation:
To arrange the given types of rock by permeability measured by hydraulic conductivity (K), we need to consider both porosity and the connectivity of pore spaces within each rock type.Limestone in a karst region is highly permeable because it often contains well-connected voids and conduits due to the dissolving action of water. Fractured granite has enhanced permeability due to the fractures, allowing water to flow more easily through the rock.
Sandstone typically has well-connected pore spaces, making it also permeable compared to other types of rock. Unfractured gneiss, being a metamorphic rock, has lower permeability due to the lack of interconnected void spaces.
Lastly, mudstone is the least permeable as it typically consists of compacted fine grains with poor connectivity, limiting the flow of water through the rock.
Based on the permeability characteristics of each rock type, the correct order from most to least permeable would be: limestone in a karst region, fractured granite, sandstone, unfractured gneiss, mudstone. Therefore, the answer is option (a).