SEQUOIA Crystal Cave in Sequoia National Park

The marble represents an old limestone changed to a beautiful crystalline form by the intense heat and pressure it experienced during mountain making movements in the earth's crust many millions of years ago. The limestone had its origin in the limy ooze deposited on the bottom of an ancient sea that covered this area in still more remote times. Since no fossils have been found in the marble, its geologic age is unknown. Deposits of sand and finer materials were interbedded with the lime until the aggregate thickness amounted to several miles. The resultant sandstones and shales also were metamorphosed, or changed, as the limestone was, to their crystalline forms we see today as quartzite and schist at Amphitheater Point or Deer Ridge overlooks. These beds were compressed into a system of mountain folds beneath which a vast reservoir of molten rock material was forced. This molten rock cooled deep beneath the surface as granite. It baked and further compressed the rocks which were intruded by it. Subsequently, but long before the rise of the Sierra Nevada, this once lofty mountain system was worn down to a monotonous plain with low hills in which the granite core was exposed. Only the roots of this folded mountain system are preserved in the granite which surrounds them. They often are referred to as "roof pendants." (17).

Marble is composed of calcite, one of the most soluble of common minerals. It can be dissolved to a slight extent by water. If the water is somewhat acid, as ground water usually is through contact with organic materials in soils and because it usually contains carbon dioxide, its ability to dissolve is greatly increased. Consequently, all the marble outcrops contain cavities, some of which are sizeable cave systems.

The passage beyond the entrance room follows a major joint in the marble.