Actually, chemical weathering is what caused the Karst topography to be present in the first place. Karst topography is defined by features that result from the dissolving of certain minerals from the bedrock layers underground. In particular, slightly acidic rainwater can dissolve calcium carbonate in limestone very slowly over geological time. This causes underground rivers, sinkholes, and caverns to appear, all of which are a part of Karst topography. As the chemical weathering of the dissolving of the limestone continues, more of these underground features appear. In addition, you can get exposed rock when surrounding debris gets washed away. This exposed rock can be chemically weathered to produce broken fault lines as the rock shifts and smooth exposed surfaces over time.