Serpentine Rock

Serpentine rock forms at California’s tectonic boundary. Water-containing sea-floor materials are pushed down as they slide under the North American Plate. The water heats up and separates from its host material. Being lighter than the surrounding rock, it moves upward.

On its journey to the surface, the water reacts with magnesium- and iron-rich minerals to form serpentinite. Serpentinite chemistry is different from rocks formed near the surface. It is poor in nitrogen, phosphorus and potassium, elements most plants depend on. Instead, it has concentrations of nickel, cadmium and mercury.

Serpentine rock – photo by Eurico Zimbres

When it reaches the surface, serpentinite outcrops prevent most plants from growing. Over time, though, some plants have adapted to this harsh environment. They cover the spaces between serpentine rocks.

Serpentine hillside – photo by Dean Wm. Taylor

Native plants have an advantage on serpentine soil because newcomers are unlikely to have had the time to adapt to it. This makes serpentine areas a great place for botanizing.

Want more? See Wikipedia and this article by the National Park Service.

Corrections/Comments: bruce@PlantID.net