The Capitan Reef
The world's best-exposed fossil reef, in a Texas desert
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A reef is an underwater ridge built up by living organisms, and the Guadalupe Mountains in Texas are such a reef, later lifted into dry land. The reef was not built by corals as modern reefs are, but by sponges, calcareous algae and microbial mats — Permian reefs worked differently. When the sea withdrew, the basin behind it evaporated and left thick salt beds, and those same layers now hold oil. The system is so completely exposed that it serves as a textbook model in geological education and in petroleum exploration worldwide.
For children
The Guadalupe Mountains in Texas are not an ordinary mountain but a petrified reef that once lay underwater at the edge of a tropical sea. Because the land was later lifted and dried out, you can walk straight through the reef and see how it was built.
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