Which region of the United States is most associated with features such as circular depressions, sinking creeks, and red clay soils?

• A. The Northeast
• B. The Southeast
• C. The Midwest
• D. The Northwest

Answer: (B)

These features point to karst topography in a warm, humid region under soluble rocks like limestone. Circular depressions are sinkholes formed when groundwater dissolves limestone, creating underground voids. Sinking creeks occur when streams disappear into these underground passages. The red clay soils indicate intense chemical weathering in a humid climate, producing iron-rich soils (ultisols) that are common in the Southeast. The Southeast has extensive carbonate bedrock and a climate that fosters karst processes and red soils, which is why these features are most associated with that region.