An arch can indeed be formed by weathering, especially when it comes to erosion caused by water. Over time, water can erode rocks and other geological formations, creating an arch-like shape. One famous example is the natural sandstone arches found in places like Arches National Park in Utah, USA. These arches have been formed over millions of years through the combined effects of weathering and erosion. So, while an arch can have other geological processes involved in its formation, weathering is certainly a significant factor.
