November 20, 2005
Unconformities are key features in understanding Earth´s evolution. In this outstanding example, the once horizontal Carboniferous rocks (ca. 320 million years old) were deformed during the Variscan-Alleghenian orogeny, producing the folds with vertical axial planes that can be seen in the lower part of the cliff. The photo was taken from Telheiro Beach in southwestern Portugal. These aforementioned folds were subsequently eroded and continental sediments of Triassic age (ca. 250 million years old) were deposited above them, providing a very useful time constraint to geologists studying the geologic evolution of Iberia.