Glossary of Karst and Cave Terms
shield; cave shield
1. A thin circular disc of calcite projecting from a cave wall at any upward inclination, commonly a meter or more in diameter and with the underside draped with stalactites and curtains. The shield is actually a double disc with a thin central crack that acts as the continuation of a wallrock fracture. It grows by water moving up the crack under pressure and depositing calcite on both sides of its outer rim. Shields are rare, but Lehman Cave, Nevada, has more than a hundred of them . 2. A disk-shaped speleothem standing edgewise at a high angle . 3. A geologically stable and undisturbed continental block .