Natural Bridge

While we were on holiday we discovered this Natural Bridge

The bridge is created in 3 phases:
1. Undermining of the cliffs by erosion forms sea caves
Sea cave, where the waves break directly on a rock cliff and are formed by mechanical erosion rather than the chemical solution process that is responsible for the majority of inland caves. Zones of weakness in the cliff give way under the force of the waves and are eroded out; these cavities are enlarged by the hydraulic pressure built up by each wave. Holes, commonly known blowholes, may eventually be forced through the roof of the cave to allow the pressure created by each wave to be released as a jet of spray.
2. With time, sea caves enlarge and form an arch like Natural Bridge
A sea arch is a natural opening eroded out of a cliff face by marine processes. Some arches appear to have developed from surge channels, which are created by wave refraction causing the focussing of wave fronts on the side of a headland. More generally, arches develop where waves attack a plane of weakness which cross-cuts a promontory. Caves produced on either side of a promontory may become joined over time to become a tunnel and, finally, an arch
3.Eventually with further erosion, the arch collapses leaving a sea stack like island Rock
Stacks can be formed by loss of the keystone of an arch in response to marine erosion. Stacks can also develop directly from erosion the cliff face or headland where the overlying rock is not strong enough to form a supporting roof. Stacks may form relatively rapidly through selective erosion along weaknesses in otherwise resistant rock. Once isolated from a host cliff the stack can become a relatively persistent feature, although we know next to nothing about the survival time of stacks. The stacks may have few joints and erode more slowly in comparison with the retreating cliff. Eventually the stack will collapse leaving a stack remnant or stump.

Source: www.britannica.com, www.landforms.eu

To log this earthcache:

1. Tell me in a few steps how the natural bridge is formed.
2. The Natural Bridge is made of various layers of sedimentary material, how many more or less can you see?
3. Observing the color, which mineral gives the color of the rocks?
4. What do you think what will happen in the future with the bridge? And which natural phenomenon will cause this?
5. (Optional) Post a photo with you and/or your team with the Natural Bridge in the background.

You are welcome to log your answers straight away to keep your TB's and Stats in order but please message us with your answers within 1 week of your log. Cacher’s who do not fulfil the Earth Cache requirement will have their logs deleted.

I have earned GSA's highest level: