Pyroxene-andesite that constitutes the Mátra was not favourable to the formation of caves. Due to tectonic movements, however, smaller cavities evolved, the largest of which is „Csörgõ-lyuk” (Rattling-hole) near Ágasvár. The formation of this cave was a result of faults. Its entrance is an 8-metre-deep hole that leads to a relatively small chamber. Branches of 25, 30 and 40 metres divide from here and at the end of the deepest branch another chamber can be found.