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When a high, rocky outcrop juts out into the water, the crashing of waves over the years erodes the base. If the layer of rock higher up stays intact as the base is worn through, a natural rock arch is carved out. |
Most people understand that erosion plays an important role in creating arches and bridges. A natural rock arch is formed by erosion. There are two types of erosive forces that account for most arches and bridges – weather erosion and water erosion.
If a crack forms in the soft layers of a sandstone fin, it allows wind to penetrate into the rock. In the desert, winds are common, and they carry lots of sand – kind of like a natural sandblaster – this can cause the cracks to widen. Acidic rain can accumulate in these cracks, chemically weakening the rock. Then, freezing and thawing frosts can cause fractured sections of rock to break off. With enough time, the constant cycle of wind, ice and rain will form an arch. This is weather erosion, and most arches and bridges throughout the world were formed this way.
Water erosion relies, as the name suggests, almost entirely on running water to create arches and bridges. Streams and rivers may eventually cut through a fin of sandstone (this is how Rainbow Bridge was formed) or acidic rain-water might pool in depressions and create an arch from above (Double Arch in Arches National Park is the perfect example of this).
Credit: NATURAL UNIVERSAL SECRETS
Picture Credit : Google
