ROCKS IN KNOTS
These Oligocene carbonate sediments exposed on the Ionian Island of Antipaxos are, to put it politely, deformed.
Rock deformation generally requires the immensity of tectonic forces (including pressure and heat) to fold, buckle, stretch and distort rocks into bizarre contortions – if you try picking up a brick, for example, and pushing and shoving it into a fold, and you’ll quickly find out that you lack the power and tenacity of a tectonic plate.
There are, however, conditions in which folds can form on the Earth’s surface relatively easily. And this is what happened at Antipaxos.
These are syn-sedimentary slump folds, meaning, they were formed by the deformation of these strata while they were still, essentially, mud on the bottom of the Oligocene sea. When these layers of muds were deposited on a slope, some small trigger (such as an earthquake) added just enough force for them to detach, and start sliding down slope – sort of a sub aquatic avalanche of slippery sediments. The sediments were in the initial stages of lithification, strong enough to hold together, but mushy enough to fold. In sliding downwards, they deformed, they rotated, they became a true mess, even as in this outcrop, looking as if they’re in knots.
Note: In addition to this amazing slump fold, geologic interests for the traveler to Antipaxos include numerable maritime caves with arched entrances, a vertical rock spire jutting out of the Ionian, excellent beaches for sand analyses, and some very remarkable local wines…
Photo by Maki Doukouros, a talented amateur photographer of Greece
http://users.uoa.gr/~vkarak/pdf/34.pdf is an excellent paper on the formation of this slump system by V. Karakitsios, M. Triantaphyllou, and P. Panoussi
An amethyst pocket in situ at Arizona, US.
The pocket was along a vein about 6 to 8 feet long. It was striking north-south and dipping about 30 degrees to the west.
I know the photo is not very attractive, but really is not very common to see these crystals in situ, unless you’re a geologist.
This is gorgeous video made up of still shots taken in 2013 on an expedition to Gates of the Arctic National Park and Preserve, the 2nd largest park in the US National Park system.
Play “Spot the structures” with this spectacle of poetry and artistic photography!