All sorts of structureThis image comes from Madeira, a group of small Portugese islands in the easte

All sorts of structureThis image comes from Madeira, a group of small Portugese islands in the eastern Atlantic. The islands are volcanic, as you can see by the vertical shafts of rock in this image. Those are dikes; they were once molten rock and they intruded into the surrounding rock as the magma forced its way upward. If you look at the edges of the dikes, you can see chilled margins – areas where the molten rock cooled extra fast. The rocks that directly contact the dikes have been slightly baked, undergoing contact metamorphism when the dikes heated them. In the center of the image, there are a couple of layers offset by normal faults. Finally, if you look closely at the dike on the left, it sure looks like there are actually 2 separate dikes sitting on top of each other; the darkest layer sure looks like a different dike than the surroundings. Its texture is different and it cuts across the fabric of the first.-JBBImage credit: https://flic.kr/p/25DFmSkReference:http://madeiraislands.net/geo…/the-origin-of-madeira-island/ -- source link

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