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The picture from our balcony was taken with an Olympus OM-D E-M10 Mark II and the other one with a iPhone 5

Wow thanks :-) Yeah the Olympus one is so rich in texture; however the iphone one is pretty rad as well!

Cg

As for what caused it; I'm not sure, though I'm tempted to do a Wiki search on cloud formations; I bet we could find something similar . . .

Cg

That's a great idea!