Before entering Colossal Cave it was essential to educate ourselves and obtain some “cave basics”. The facts and information we learned about limestone caves made our trip profoundly interesting!
Colossal Cave is an archaic KARST CAVE (meaning erosion has produced fissures, sinkholes, caverns and underground streams).
Karst caves have 3 categories: limestone, gypsum and quartzite.
Colossal Cave is limestone and considered dormant, “dry”. A dry cave is without drips of water, streams or pools. How was the cave formed? Here is a short, simple answer:
- Precipitation mixes with carbon dioxide from the atmosphere and decaying organic material in the soil.
- When Carbon dioxide is dissolved in water it forms carbonic acid. The carbonic acid begins to form holes in rocks, seeps into crevices and dissolves the rocks, especially limestone; but very slowly. (Thousands of years)
rock crevices and joints.
- Cavities form and further sculpting can occur from water and chemical weathering.
- After passing through limestone, the acid water contains a dis-solvable calcium carbonate. As this solution de-gases through exposure to air by way of splashing, dripping or flowing, it loses carbon dioxide and deposits a solid mineral called calcite.
- Calcite is the main mineral component in CAVE FORMATIONS, (speleothems).
The SPELEOTHEMS in Colossal Cave no longer grow. This cave formed by water depositing limestone that has NOW disappeared. Close by, in the same mountain park, are Arkenstone and La Tetera Caves with active growing formations.
The most abundant mineral in limestone is calcite (calcium carbonate). The majority of limestone formed on ANCIENT ocean floors.
Calcite is a main component used by echinoderms, like sea urchins, starfish, and sand dollars to make their spines and skeletons. Calcium carbonate (calcite), is found in the shells of marine organisms and truly is one of the MOST abundant minerals on earth!
In the marine environment, if the conditions are right, calcite is stable enough that it can cement together sediments and overtime make limestone.
On occasion another element may be present while calcite is being formed (ex: magnesium) and take the place of a calcium atom.
A less stable aragonite is a polymorph of calcite. They are both calcium carbonate but have different crystal shapes and symmetries. The calcium, oxygen and carbon atoms in aragonite bond together differently creating a unique crystal structure.
Ok this is plenty of background information so now journey with us to Colossal Cave Mountain Park!
The elevation of Colossal Cave Mountain Park is about 3,500 feet. The temperature of the cave averages 70 degrees Fahrenheit. No extra clothing is needed but feel free to carry water or a camera.
Frank Schmidt was monumental in the improvements and preservation of Colossal Cave by handing over his leases to the State of Arizona. You can find information and historical photographs at La Posta Quemada Ranch Museum.
In 1879, Solomon Lick, the owner of the nearby hotel, was searching for stray cattle and discovered the entrance to this cave.
Thousands of years ago Colossal Cave was used by Hohokam, Sobaipure and Apache Indians. Travel down the road to the ranch museum for a fascinating display.
Most crystals are found in areas, like caves, because they take thousands of years to grow. The growth continues until the saturation is stopped or the cave dries out. Most crystals in a cave are calcite or aragonite.
Your tour guide will tell the story of the bandits who hid out in Colossal Cave. These outlaws even played cards in the Colossal Cave Living Room. Legend has it that the gold from the train robbers is still inside the cave!
Stay with the tour group. Our guide really wasn’t kidding when she said the group might go left and you’ll go right and be lost for hours in Colossal Cave.
Tectonic activity is noticeable. Your guide will point out a fault in the earth’s crust.
Cave’s formations, speleothems, are created by the same water that dissolved the calcite in the limestone —- then deposited the calcite in other areas of the cave.
Stalactites – “c” for ceiling – hang from the top of caves like icicles
Stalagmites – “g” for ground – emerge from the ground like a traffic cone
Because Colossal Cave is DRY; the appearance of these speleothems is different than living caves.
In the 1930’s, a Civilian Conservation Corps designated by President Roosevelt worked tirelessly building the retaining wall outside and improving the inside of Colossal Cave.
The CCC, Civilian Conservation Corps, constructed the stairs, bridges and handrails.
While visiting this cave do adventure down the road to La Posta Quemada Ranch.
Colossal Cave and the historic La Posta Quemada Ranch are listed on the National Historic Register. When you visit be sure to enjoy a Desert Spoon Burger!