What is one primary characteristic of arches formed in limestone rock?

The primary characteristic of arches formed in limestone rock is their curved structure. This curvature is a result of the erosion and weathering processes that act on limestone, which is a sedimentary rock. Over time, water can seep into cracks in the limestone, dissolving the rock as it flows through. This dissolution weakens sections of the rock, leading to the formation of arches via a process known as karst topography. The distinctive curved shape of these arches allows them to span gaps or openings, providing both structural integrity and aesthetic appeal. In contrast, substantial height, flat surfaces, and thick layers do not specifically define limestone arches, as these features can vary depending on the rock's geological context and erosion patterns.