IF YOU ARE interested in unusual natural habitats and are traveling to eastern Pennsylvania in the Mid-Atlantic region of the United States, you should be aware of our small cluster of serpentine barrens. This globally rare soil type results in unusual plant communities. Serpentine is a metamorphosed ultramafic type of rock that is formed when sea- floor rocks high in magnesium and iron are metamorphosed by heat and contact with seawater as continents collide. The name mafic is derived from the chemical symbol Ma for magnesium + Fe for iron. Adding the prefix ultra, of course, means they contain a very high percentage of these metals compared to most rocks. There are many outcrops of ultramafic rocks around the world, but they only make up a small percentage of the land surface of the continents. (Brooks, 1987)
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