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Gibraltar limestone
The famous Rock of Gibraltar has overlooked the entrance to the Mediterranean Sea throughout all of human history. Its dominant position has made it a strategic asset, leading to it being conquered over and over again, most recently by the British, who count it as part of their territory to this day.
The story of the Rock of Gibraltar starts almost 200 million years ago during the Jurassic period. As Pangaea broke apart, there was a huge ocean separating Africa and India from the rest of Asia. That ocean, known as the Tethys Seaway, flooded some portions of the land at the coasts and allowed limestones to be deposited on the shelf. The Rock of Gibraltar is made mostly of the Gibraltar Formation, one of these limestones. It even contains fossils.
About 20 million years ago, Africa was impinging on Europe and beginning to thrust up mountains. The sediments that once sat on the shore of the Tethys Seaway were caught up in this continent collision. They started off as wide, flat-lying beds, but the force of two continents ramming together caused them to fold again and again. The Rock of Gibraltar is part of a specific type of fold called an overturned Anticline.
To understand this kind of fold, I can offer an exercise or a metaphor. Take a stack of paper and lay it flat on your table – this is like the flat-lying limestones that formed in the Jurassic. Now, push the two edges of that paper together and make it fold all the way up; you’ve now created a tight fold called an anticline. Now, tip that fold over to the side, and you have overturned that anticline.
One of the most interesting parts of this fold style is that part of an overturned anticline actually winds up upside down. On one side of the fold, the youngest rocks are on the top, but on the other side of the fold, there are older rocks (at the core of the anticline) sitting on top of younger rocks. This is the case at the Rock of Gibraltar; the upper limb of the fold has totally eroded away, leaving behind only the overturned limb. At the rock of Gibraltar, the older rocks are actually on top and the younger rocks are on the bottom.
There is a weak, poorly lithified, shale unit that sits in this sequence above the Rock of Gibraltar. However, with the overturned limb, the limestone sits on top of that shale. Where the shale is exposed, it erodes easily, undercutting the limestone. The limestone cliff breaks off when the shale holding it in place erodes, leaving behind steep cliffs and skree slopes.
-JBB
Image credit: http://bit.ly/2FFYKLA Reference: http://bit.ly/2DXxAiQ
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Space Station flight from a clear North Africa over a story Mediterranean
Ok apparently sailboat races look amazing in timelapse.
Lenticular cloud over the rock of Gibraltar - when it zooms in you can really see how the cloud appears as the air moves over the obstacle!
The first confirmed Neanderthal art These 40,000 year old abstract marks in the dolomitic limestone of Gibraltar are the oldest European art, and it wasn't made by us. About a year ago we reported on a controversial hypothesis based on new dating methods that suggests our Neanderthal cousins may have had a hand in the world renowned cave paintings at Altamira in Spain (see http://tinyurl.com/lycavqd). A series of marks found in Gorhams cave, in a layer associated with typical Neanderthal tools (a style known as Mousterian after a town in France) seem to be the first definite proof of Neanderthal artistic ability, a possibly that has been bitterly contested by many experts until now. They fought a valiant rearguard action against the possibility that our might have spoken, until a Neanderthal hyoid bone was discovered (the floating bone in the neck from which the larynx, containing the vocal chords, is suspended). Similarly the possibility that they might have been capable of art or abstract thought has been rejected since the earliest days of human palaeontology. Neanderthal seems to have evolved separately in Europe from Homo erectus, during the last half million years, while Homo sapiens was simultaneously evolving in Africa. As well as being our cousins, they were also ancestors to some of us (seehttp://tinyurl.com/mzm2h3e for more on out genetic links). Researchers posited that their stupidity was the reason that they were supplanted by our good selves, but recent research suggests small communities and low genetic diversity may have been the actual cause (see http://tinyurl.com/kfogbqq). The marks were discovered in 2012 on a small ledge a hundred metres in, and measure about 3 square metres. There is no clue as to what meaning the minds and hand that created them might have intended. The stratigraphy seems conclusive, the sediments burying the marks were undisturbed in the intervening millennia, and the tool assemblage within that sediment (overlying the marks) is clearly Mousterian, of a type never found in Homo sapiens sites. The dating proves that they were made long before we were in southern Spain. Loz Image credit: Stuart Finlayson http://www.theguardian.com/world/2014/sep/02/neanderthal-abstract-art-found-gibraltar-cave http://news.nationalgeographic.com/news/2014/09/140901-neanderthal-engraving-gibraltar-science/ http://news.discovery.com/human/evolution/could-cave-carving-be-first-neanderthal-art-140902.htm http://www.bbc.com/news/science-environment-28967746 http://www.independent.co.uk/news/science/neanderthal-art-created-40000-years-ago-found-in-gibraltar-cave-9705810.html