1The Beginning
How old are the Caverns? When did they begin to form? Are they growing larger today? What changes, if any, are now going on?
These are questions which everyone who becomes interested in the great Carlsbad Caverns wants to have answered sooner or later.
To some of these and many similar questions the answers are difficult to obtain, for when the Caverns were being created no man was around to watch the process and to report his observations first hand. As a result, we have only the word of geologists and other scientists who have specialized in the study of the earth, its formation, and the changes that have come about through the countless ages since our world began.
No one knows how old the Caverns are. All man can do is to estimate, and he bases these estimates on a study of conditions he finds within the cave itself, in the surrounding countryside, and from a general knowledge of the earth and how it has evolved.
Probably the area itself began to form about 200 million years ago, during the Permian period of geologic time.
The area at that time is supposed to have been either an inland sea or a shallow extension of the ocean. During this Permian periodthe earth's surface was changing. Mountains were rising and the waters were receding, thus greatly enlarging the land areas. Amphibian life was on the wane, and reptiles began to appear.
Great thicknesses of limestone deposits were made during these countless centuries, some in the form of a reef now known as the Capitan limestone. Contemporaneous rock behind the reef is called the Tansill formation. It is in these rocks that the Carlsbad Caverns are located.
Since Permian time geologists think the seas may have risen again and covered what is now New Mexico, leaving sediments that have been largely removed. About 60,000,000 years ago, during the Cretaceous period when coal was being formed elsewhere in the world and dinosaurs roamed the earth, the land was uplifted, perhaps producing cracks and crevices in the limestone.
Geologists at one time believed the Caverns were caused by the action of water as it flowed down through the limestone, dissolving as it did so minute particles of the stone. Today, however, that theory has been discarded, since a more careful and detailed study indicates the Caverns to have been formed by phreatic solution, their development resulting from a two-cycle method of creation.
The Caverns can be said to be a natural cavity in the earth formed by the solution of rock by subsurface waters. Actually, there are two great geological processes involved in the formation of the Caverns. The first came about as the water hollowed out the underground chambers, and the second took place when the formations of stone were created in these underground openings.
To be explicit, we can only say that the Caverns are large crevices or cracks in the limestone which have been enormously enlarged by the constant solution of the rock into the underground water which filled these indentations.
In order to understand just what the two-cycle method means and how it can exist, we must first understand the two conditions under which these operations of nature can take place.
Water, as it seeps downward into the earth, tends to seek what we shall call its own level. This would be a point where everything below is saturated with water, the water table of the region. Above the table water works downward due to its gravitational pull. Below the table there is only rather slow movement of water.
The area above this point is known as the vadose zone, and below this point the area is the ground-water or phreatic zone.
Any farmer who has ever sunk a well knows how important it is that his well reach below the water table if he is to be assured a continuous supply of water. Well owners also know that the water table can rise or fall due to any of several natural causes, such as an abundance of rainfall for a few seasons, or any great lack of rainfall for an extended length of time. When the water table goes below the lowest reaches of the well, no more water can be pumped, and it is necessary to extend the well further into the earth until it again goes below the water table and reaches into the saturated area where water is abundant.
The water table is not constant around the world, even though water seeks its own level. The water table might be high in one section of the country, low in another. It might be kept high by an abundance of rain, or remain low due to outlets such as springs or underground seepages.
The vadose-water area also varies, and the effects created by the rise and fall of the water table in one section of the country, for example, might be vastly different than the effects in an adjacent territory. This explains why any action of underground water in one area is not necessarily duplicated in an apparently identical area close by.
With an understanding of the two water zones, and the demarcation line between, we can more readily comprehend just how the Caverns were formed.
Geologists are now pretty well in agreement that the enclosing rocks of the Caverns were located in the ground-water zone under saturated conditions. As we already know, large cracks existed in the otherwise solid limestone.
Then, for many, many years the ground water dissolved the limestone, enlarging the cracks bit by bit, until the huge Caverns were formed. At this point the water table was lowered, and, in time, the Caverns ceased to exist in the ground-water zone. Following the lowering of the water table, the Caverns were nothing more than empty holes in the earth. Now the second phase of their "growth" was to begin.
When the ground water could no longer continue its constant gnawing action on the limestone, the Caverns had reached theirmaximum size. From now on they would begin to fill up again.
The second of the two cycles consisted of mineral deposit brought about by water seeping downward from the surface, carrying lime for the secondary formations which are today one of the great features of the Caverns.
Water in the vadose zone, seeking the ground-water level, would seep into the top of the many rooms and galleries. Each drop contained a minute portion of limestone.
Some drops would remain on the ceiling, where the moisture would evaporate, leaving a tiny ring of limestone deposit behind. As these limestone deposits accumulated they formed a pendant mass resembling an icicle which is called a stalactite. Drops falling to the floor would produce deposits known as stalagmites.
Sometimes the stalactites and stalagmites would join and a solid pillar would be formed.
In the rocks enclosing the Caverns are various deposits of other minerals such as iron oxide which are often carried in minute quantities within the seeping water and deposited on the stalagmites and stalactites. These minerals are responsible for the many different colors that may be seen in many places within the rooms of the Caverns.
Some of the formations have a very live and transparent appearance, looking somewhat as though they might have just been given a thorough coat of wax. Actually, these formations are still active. That is, they are still covered with water and the age-old process of depositing the small particles of carbonate of lime contained in the water is still going on. In cave parlance they are "alive", that is, they are still growing.
In the Carlsbad Caverns today about 10 per cent of the formations are "alive". Water is seeping in around them and working its wonders. It is this presence of water that gives them the polished, radiant look.
When the water no longer reaches the formations, they "die", i.e., they no longer continue to grow. They lose their sheen and lustre and take on a powdery appearance.
Geologists differentiate the two primary effects of seeping water in the creation of the formations in caves. Those that are created by water dripping from above, as in the case with stalactites and stalagmites, are referred to as dripstone formations. Those created by theflowing of water over a surface are called flowstone formations. In some rooms of the cave, formations made of flowstone are quite abundant. This is to be found mostly on the floors of the rooms, or on walls where a large volume of water is present. These formations have been referred to as masses which resemble ice that forms on a cold winter's day near a stream of water. Others have described them as "cascades frozen in stone."
An additional phase of the cave's development has been described by geologists as the period of collapse. During the centuries when the entire area was saturated with water, limestone blocks on walls and ceilings were weakened by solution, later to crash to the floor, leaving the room larger than ever. This collapsing continued after the cave became "dry" but ended once stability was achieved. Park naturalists tell us no rock has fallen within the cave for thousands of years.
So ends the first stage of the history of the great Carlsbad Caverns, their gradual growth and formation over periods of millions of years. Man was still centuries away when their beauties were being created. But were other forms of life inhabiting them?