Thousands of years ago, the area around the Ohio Caverns was covered by water. When
the plants and animals living in this sea died, they fell to the bottom. Over time, these plants and
animal skeletons were pressed and cemented into a rock called limestone. Later, the limestone
was lifted from the sea by the same force that built the mountains of the world. When the fresh
rain falls and passes through the soil, it reacts with carbon dioxide to form carbonic acid. The
carbonic acid then reacts with minerals in the limestone, as well as dissolving the limestone
itself, creating passageways surrounded by undissolved rock. (See Activity #1)
If the water table lowers, or if the surface above the cave becomes worn away, the system
becomes open to air. The water seeping through the limestone carries with it tiny bits of
dissolved rock and minerals. When the water encounters an open cavity, left by the receding
water, it begins to evaporate, allowing the dissolved matter to solidify. Over thousands of years,
the layers of minerals build into formations. This is how speloethems are formed. Stalactites are
found hanging from the ceiling, while stalagmites grow from the floor up, the result of excess
water and minerals dripping from the stalactites. Speleothems can differ in shape and color
depending on the mineral composition. The most common mineral formations in limestone
caves and caverns are made of calcium carbonate of limestone, or calcite. However, if iron
oxide (rust) combines with the calcite, the formations may be given an orange tint. Likewise,
manganese dioxide causes the formations to appear slightly blue. (See Activity #2)
The formation of speleothems is a very slow process. The environment of caves and
caverns is very humid. However, the temperature is usually very mild. For example, the
temperature inside Ohio Caverns remains 54o F throughout the year, while the humidity is
constantly above 90%. These conditions do not promote rapid evaporation of water. At Ohio
Caverns, the growth rate is approximately 1 cubic inch every 500-1,000 years. The humidity is
very important to the cave environment, keeping it wet and allowing formations to grow. During
wet years, the mud floor will store the water. In dry years, the water in the mud will evaporate
once again, keeping the environment humid. (See Activity #3, Activity #4, and Activity #5)
It is very important that visitors to any cave or cavern refrain from touching any of the
formations. Many formations are very fragile and will break very easily. Since it took thousands
of years to form each speleothem, it would also take thousands of years for the broken formation
to grow back. Oil and dirt from people’s hands can also damage the formations, not only by
changing the color, but also by forming a barrier to the water. The oil causes the water to run off
the formation too fast to allow minerals to be deposited, so they will not be able to grow. (See
Activity #6)
People who explore caves and caverns are known as spelunkers. There are safety rules
that each spelunker should follow. First, no explorer should go into a cave or cavern alone.
Even with a friend, a person outside the cave should be notified as to where the cavers will be.
This way, if the spelunkers have not returned after a long period of time, rescuers will know
where to search. Another rule is that every spelunker should have the proper equipment. Since
caves are often cold and wet, gloves and boots are often necessary. Crawling over sharp rocks
can be painful if an explorer does not have knee and elbow pads. In larger caves and caverns,
ropes and harnesses may also be required. However, the most important pieces of equipment of
any caving expedition are flashlights and helmets. Helmets protect the wearer from serious head
injuries in addition to providing a light source in the form of a headlamp. Each explorer should
also carry two flashlights, for a total of three sources of light. (See Activity #7)
Because it is a cavern, nothing has ever lived in Ohio Caverns. Caverns are sealed off
from the surface, but caves have natural openings, allowing people and animals to use them for
shelter. Many different types of animals can live in caves, and most of them have developed
specific adaptations that make them better able to live in the dark, damp environment. For
example, a bat’s echolocation allows it to maneuver through the dark passageways. Some caves
have blind fish living in them. They have no use for eyes in total darkness, so they evolved to
grow without them. (See Activity #8)