Mesas, Capitol Reef National Park, Utah, USA

© Tim Fitzharris/Minden Picture

The rocky ‘reef’ of Utah

We’re in Capitol Reef National Park, in the western US state of Utah, which was established as a national monument (protected land usually created by the president) on this day in 1937. Its name comes from its massive sandstone domes, which reminded explorers of the famous domed Capitol Building in Washington DC. And where does the reef bit come from? Those imposing formations were a major obstacle to travellers through the region, in much the same way as a coral reef is an obstacle to sailors.

But the section of the park in our homepage image, Cathedral Valley, is dotted instead with monoliths featuring sheer, jagged walls. While most of the park rests on a steeply warped section of Earth's crust, Cathedral Valley is relatively flat - so rather than carving out gently sloping domes, water erosion here has tended to cut deep, narrow recesses down the rock faces.