The layers are especially thin in the lower part of the formation, with alternating light and dark beds. At the bottom of the Manlius formation is a three to four feet thick, finely bedded lime murdock known as Rundout waterlime. This was named after the extensive quarries and cement mines in the vicinity of Rondout. It was mined for the manufacturing of natural or Rosendale cement. Here you can see the characteristic cracks and vertical joints in the limestone.
Fissures develop and become larger as the limestone is dissolved by the rain water.
Rain absorbs carbon dioxide, as it passes through the atmosphere and decaying organic matter in the soil, and becomes less acidic. This enables the ground water to slowly dissolve the limestone. The large amounts of limestone in John Boyd Thacher State Park have certain associated natural phenomena. The solubility of the limestone explains the occurrence of disappearing streams, underground streams, caves and sinkholes. Underground streams from as surface water seeps into the joints of limestone and eventually dissolve passages through the rock.