The question asks about the type of plains formed specifically due to the weathering of soluble rocks like limestone and dolomite. This type of weathering involves the chemical dissolution of the rock by water, especially acidic water.

Understanding Karst Plains Formation

Karst landscapes and formations are created primarily by the dissolution of soluble rocks, most commonly limestone (\(\text{CaCO}_3\)), but also dolomite, gypsum, and salt. When rainwater, slightly acidified by dissolved carbon dioxide from the atmosphere and soil, percolates through fissures and cracks in these rocks, it chemically reacts with and dissolves the rock material. This process is known as carbonation or dissolution.

Over long periods, this dissolution process enlarges cracks and fissures, leading to the formation of characteristic karst features such as:

• Sinkholes (dolines)
• Underground drainage systems
• Caves
• Underground streams

When extensive dissolution occurs across a region with relatively flat or gently sloping terrain, it can result in the formation of Karst plains, which may be dotted with sinkholes, depressions, or remnants of resistant rock.

Why Other Options Are Incorrect for Soluble Rock Weathering

Let's consider the other options provided:

• Desert Plains: These are typically formed in arid or semi-arid regions primarily through processes like wind erosion (deflation and abrasion), mechanical weathering, and occasional water erosion. While chemical weathering can occur, the dominant processes and resulting landforms are distinct from those caused by the dissolution of soluble rocks.
• Deposition Plains: These plains are formed by the accumulation of sediments transported by agents like rivers (alluvial plains), wind (loess plains), or glaciers (outwash plains, till plains). Their formation is about adding material, not dissolving bedrock.
• Glacial Plains: These plains are formed by the action of glaciers, either through erosion (creating flat, scoured surfaces) or deposition (forming till plains or outwash plains from glacial meltwater). The primary process is mechanical erosion and deposition by ice and meltwater, not chemical dissolution of soluble rocks.

Therefore, the formation described, involving the weathering of soluble rocks like limestone and dolomite, specifically defines Karst plains.

Conclusion on Plains Formed by Soluble Rock Weathering

Based on the processes of landscape formation, plains resulting from the chemical dissolution and weathering of soluble rocks such as limestone and dolomite are classified as Karst plains. This geological process leads to a unique topography characterized by features related to underground drainage and dissolution.

Revision Table: Types of Plains Formation

Understanding the different ways plains are formed helps distinguish them. The key difference here is the chemical process involving soluble rocks versus mechanical processes like erosion and deposition by other agents.

Additional Information on Karst Landscapes

Karst topography is not limited to just plains; it includes a variety of landforms. Besides sinkholes, caves are a very common and significant feature, often containing speleothems like stalactites and stalagmites formed by the deposition of dissolved minerals. Larger depressions can form from the collapse of multiple sinkholes, creating uvalas or even larger, elongated depressions called poljes. The drainage in karst areas is predominantly underground, leading to a lack of surface streams in many places.