Natural stone arches are geological formations that occur when rock is exposed to significant amounts of erosion, which over time forces the rock to form an arch. Stone arches are among the most diverse rock formations, not only due to the vast area in which they are found, but also due to their complex ways of formation. While many factors contribute to making natural stone arches so fascinating, one key role maintains and sharpens our constant focus: every single stone arch, whatever its shape, will fall. Despite what we know about stone arches, they are constantly changing and teaching us new things about them and the world around us. All naturally occurring stone arches are formed by the selective erosion of rock, but the terms under which this can occur are enormous. Among the most frequent types of formation are wave action and lava flows. During wave action, water constantly crashes into rock, effectively accelerating erosion while the sediment carried by the water is extremely abrasive, removing fragments of rock. When the lava flow occurs, la la...