Have you ever wondered about caves and how they got here? These pages are dedicated to helping our viewers to learn about caves. Each month we will be adding to this section with more information about caves and caving.
Stages In Cave Development
Stage 1: At a certain depth below ground, even in the arid Southwest, there is a surface below which every pore and crack is filled with water. This surface is the water table. The first stage involves enlargement of cracks by slowly moving acidic groundwater in the region just below the water table.
Stage 2: The first large cave tunnels form when large amounts of limstone are dissolved by carbonic acid. Most carbonic acid originates from decaying vegetation in the soil above the cave. The acid is simply carbon dioxide (CO2) dissolved in water. It is the same substance that gives carbonated drinks their "fizz."
Stage 3: The water table is lowered due to erosion outside the cave. A new "lower level" of passages may form, and the upper levels become air-filled. Downward-moving waters erode passages and introduce silt and clay. In this and earlier stages, limestone is dissolved rapidly because of the large amount of CO2 (carbonic acid) in the cave water and air. The cave has no entrance as yet, and no decorations.
Stage 4: Surface streams erode an entrance into the cave. At this point, and not before, cave decorations such as stalactites begin to form. Making an entrance is exactly like opening a carbonated drink: the CO2 bubbles out. Without CO2 the water is less acidic: it can no longer dissolve limestone. Cave passages cease to grow. In fact, the water can no longer hold its already-dissolved limestone, so this is deposited as stalactites and decorations.
Stage 5: Collapse of the cave is the final stage. Often, early signs of the cave's demise include drying out of the passage due to lowering of the water table and air circulation from multiple entrances. Also, blocks of rock, called breakdown, begin to fall from the ceiling. When enough of these blocks fall, the weakened ceiling can collapse altogether, resulting in a big hole filled with rubble: a sinkhole.