Petty John's Cave popular destinations of the cave. Formations in Petty John's Cave include: Stalagmites that are a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. Stalactites are also found in the cave. These formations hang from the ceiling or wall of the cave. There are also pillars, soda straws, cave pearls, flowstones, and cave popcorn are other formations in the cave. In addition, waterfalls can be found in the stream passage section. This cave hosts tri-colored bats during their winter hibernation because temperatures are low
Cave of the Mounds National Park Service designated the cave as a National Natural Landmark. The limestone from which the cave was carved began forming approximately 488 million years ago, during the Ordovician Period. During this time, much of North America was covered with warm, shallow seas. Over millions of years, calcium carbonate shells from tiny marine organisms accumulated on the sea floor, forming enormous quantities of limestone. The type of limestone in which the cave was formed is called galena dolomite because of its high concentration of the lead ore galena. The cave began forming about a million to a million and a