![landscape arch before and after landscape arch before and after](https://i.pinimg.com/originals/28/8b/f8/288bf8922d470ceef2f66293735e2481.jpg)
Some weathering and erosion processes are more effective near the ground than high up. Weathering processes attacked the rocks along these joints, which were slowly widened to leave vertical slabs of rock called fins. The most common joints formed by this motion are parallel, nearly vertically oriented, and a few yards (or meters) apart. However, the foil wrapping of a fast-food packet is fairly flexible, but the Entrada sandstone was not, so as the salt moved, the tough sandstone broke. When the weight of those sediments became large enough, the salt began to flow, squeezed from places where thicker sediments caused higher pressure on the salt, to places where thinner sediments gave lower pressure, like ketchup in a fast-food packet squeezed from one place to another. Sediments including the Entrada sands were deposited on top of the salt, and cemented by hard-water deposits to make sandstone. Arch formation started with deposition of thick beds of salt in the Arches area.
![landscape arch before and after landscape arch before and after](https://i.pinimg.com/originals/81/0f/00/810f007fe5102d3ba41ff2e5b7efe2f7.jpg)
The arches are all eroded in sandstone, and especially the mid-Mesozoic (deposited during the time of dinosaurs) Entrada Sandstone, which includes both marine and wind-blown sands. The trail under the arch has been closed the Park Service knows that eventually more rocks, and the whole arch, will fall, and the rangers do not wish to be involved in extracting compacted humans from beneath the remnants of what used to be the world’s longest arch. Several rockfalls have occurred from Landscape Arch since European settlers arrived, reducing the arch to a thickness of only 11 feet in one region. The longest natural arch in the world is there, Landscape Arch, spanning about 300 feet (almost 100 meters). Arches contains the largest concentration of natural stone arches in the world, with dozens of major arches, and numerous other holes and interesting rock features. Arches National Park is just outside of Moab, Utah, almost within shouting distance of Canyonlands.