Correct Option
The correct option is 1 and 3 only.
Explanation
Karst topography develops in regions with limestone or dolomite rocks, where groundwater acts as a significant agent of erosion through the chemical process of solution (dissolution of calcium carbonate). The resulting landscape is characterized by specific erosional and depositional landforms.
Statement-wise Analysis
- Statement 1 is Correct: While strict definitions distinguish sinkholes as the depression and swallow holes as the specific opening where streams disappear, these terms are often closely associated. In the context of this question, the description of "small to medium-sized shallow depressions formed by solution" is accepted for swallow holes/sinkholes, distinguishing them from larger features like Uvalas.
- Statement 2 is Incorrect: Uvalas (or valley sinks) are extensive depressions formed by the coalescence (joining together) of multiple sinkholes and dolines. While collapse may play a role in their expansion, their defining process is the merging of smaller depressions into a large, trench-like feature, rather than the collapse of a single sinkhole.
- Statement 3 is Correct: Solution sinkholes are frequently covered by a thick soil mantle. This soil cover can clog the drainage or conceal the rocky opening, causing the depression to fill with water and appear as a shallow water pool on the surface.
Key Takeaway
Sinkholes are the most common erosional landforms in Karst regions. Swallow holes are the openings through which surface streams descend underground. Uvalas are larger compound depressions formed by the merging of multiple sinkholes.