Talus cave

A talus cave, also called a boulder cave, is a cave formed by the voids between one or more large boulders, and such caves occur wherever sizable boulders have piled up, particularly in scree at the base of cliffs. They form in many rock types, including anorthosite, schist, slate, phyllite, conglomerate, marble and sandstone, but form most readily around strong, cleanly fracturing rock such as granite or gneiss. At the base of cliffs, mass movement and landslides pile up the scree that contains the caves; in steep gorges, slope failure combined with a stream cutting downward can wash smaller stones and soil out from beneath large boulders and leave a cavity behind; and in Scandinavia and other recently glaciated regions, many talus caves formed through neotectonic fracturing after glacial rebound, when earthquakes broke apart roche moutonnee hills into networks of fractures and cavities.