The White Stairs

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This amazing site is a beach in southern Sicily known as Scala dei Turchi. It is a popular beach and tourist destination, both for the views and for the water, which is rich in sedimentary mud coming from the exposed outcrop. The rocks are considered marls: a mixture of extremely fine-grained carbonate and clay minerals placed down in alternating layers. The rocks are late Miocene to Pliocene in age, starting formation about 10 million years ago.

The layers alternate between more and less resistant to erosion, creating a stairstep pattern. The layering forms because of variation in the ratio of silicate minerals to carbonate minerals and relate to changes in the global climate as the planet approached the recent ice ages. When the Mediterranean Sea area was warmer, it led to more productivity in the surface waters and more carbonate delivered to the seafloor. When the area cooled, productivity in the waters decreased and more sediment was picked up from the cooler, drier continent and delivered to the seafloor by the wind. This stairstep sequence therefore is a record of the climate swinging back and forth between colder and warmer, driven by variations in the planet’s orbit and the concentration of greenhouse gases in the atmosphere.

The rocks have since been uplifted and tilted by the collision between Africa and Europe that is building mountain ranges throughout the area. Source: The Earth Story

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