Millions if years in the making, the Natural Bridge has been sculptured by the relentless power of water, waves and wind.
The banded gneiss that forms the Natural Bridge contains a set of vertical and horizontal joints. These were formed by tectonic forces and through pressure release as the gneiss slowly cooled and was exposed at the surface.
Groundwater penetrated the gneiss along the joints, gradually widening them to form a network of rectangular blocks.
At the surface, waves, saltwater spray, rain and groundwater continued to penetrate the joints, causing the minerals to rapidly weather and form clay. The clays were constantly washed away, ever enlarging the joints and allowing more water to further erode them.
Over many thousands of years, the impact of waves caused blocks of gneiss to detach and fall into the sea, gradually sculpturing the sea cliffs to form the Natural Bridge and The Gap that we see today.
Wave action eventually removed the lowermost blocks to form the Natural Bridge.
Continued weathering will cause the Natural Bridge to eventually collapse.
In order to claim a find on this earthcache, answer the following questions:
1. Name the two distinctive rock types at the Gap and Natural Bridge that resemble granite.
2. What minerals cause the darker layers in the rock?
3. What crystals form a interlocking mosaic making it a very hard and strong rock and resistant to weathering?
Optional add a photo or two of your visit.