Limestone Pavement With the aid of a diagram(s), explain how chemical weathering has shaped the limestone pavement in a karst region. - Leaving Cert Geography - Question B - 2012

A diagram illustrating the impact of carbonation on limestone pavement should include:

• Limestone rock depicted with cracks and joints.
• Rainwater containing dissolved CO2 percolating into the rock.
• Representation of the resulting karst features, such as grikes (the deep fissures) and clints (the raised blocks of limestone).

Ensure that the diagram is clearly labelled to receive full marks.

In a karst region, chemical weathering through carbonation results in the dissolution of limestone's calcium carbonate (CaCO3), leading to remarkable geological formations.

1. Process of dissolution: When the carbonic acid in rainwater reaches the limestone, it reacts with the calcium carbonate, resulting in the dissolution of the rock: $ext{CaCO}_3 (s) + ext{H}_2 ext{CO}_3 (aq) \rightarrow ext{Ca}^{2+} (aq) + 2 ext{HCO}_3^{-} (aq)$

2. Formation of features: Over time, as more limestone dissolves, features such as grikes and clints develop, creating unique landscapes characterized by rugged pavements. This evolution leads to increased surface area for further weathering processes.

3. Environmental conditions: The rate of chemical weathering in these regions is influenced by factors such as rainfall, temperature, and the presence of organic material, which can increase the acidity of rainwater and enhance the weathering process.

In summary, carbonation is a key chemical weathering process that shapes limestone pavements, contributing to the distinctive features observed in karst landscapes.