More On The Work of Groundwater

Jewell Cave, South Dakota

For us groundwater folks there is nothing more important than...groundwater.  After all, in sheer volume, our under-the-earth resource dwarfs the amount of fresh water in all the lakes, rivers, streams, swales, bayous, creeks and whatever else holds fresh water on top of the land.  It also does a yeoman's job of supplying fresh water for humanity - from drinking water to irrigation to industrial and every other use there is.

So what other work does groundwater do?  The extra job I'm going to talk about today is forming caves - not all of them, but groundwater plays an integral part in the formation and/or existence of many caves around the world.  One of the more interesting jobs in this line is the work groundwater did in the Jewell and Wind Caves in the Black Hills region of Southwest South Dakota around the town of Custer.

To make a very long story short (pardon the pun) the Black Hills uplift some 70-40 million years ago thrust the largely igneous basement rocks up through the overlying sedimentary rocks - including the two major regional formations known as the Madison Limestone (300-450 feet thick) and the Minnelusa Sandstone lying on top of the Madison.  The central dome has since been eroded away exposing the igneous and metamorphic rock which is completely ringed by the sedimentary formations that dip gently away in all directions.  It is in the Madison Limestone where these vast caves exist.  Jewel Cave is the second longest series of cave passages in the world - some 160 miles of currently mapped passageways.  There are undoubtedly more, but mapping this extremely complex labyrinth has not been completed. 

The real story of the role groundwater has played is also still undetermined for sure.  There are 4 theories as to how these were formed, and all of them involve groundwater, but no one knows for sure - yet.  They are:  (1) rising thermal waters through time; (2) confined groundwater moving down-dip to springs; (3) infiltration through the porous sandstone; and (4) relics of the 300-million-year-old paleokarst.

The fact that both caves exist in the middle area of the Madison is perplexing.  The passages don't extend down dip very far, they rarely reach up and connect with the overlying Minnelusa Sandstone, and they don't reach down to the base of the Madison limestone either.  In fact, in Jewell Cave, they don't even intersect the current groundwater table.  However, while the precise role groundwater has played is not known, few doubt that groundwater somehow did this over time.  For a much more technical rendering of these caves, click here.

I'd like to help map the rest of these caves, but I'm afraid my girth alone would prevent it in all but the largest passageways.  Besides, I don't like dinky dark dank dens - be they associated with groundwater or not.
 

Cave Rock, Water Babies and the Washoe People

Cave Rock sits at the very edge of Lake Tahoe along its East side about 1/3 the way up from the southern tip of the lake.  It is a sacred place to the Washoe people and happens to be the place where the legendary Water Babies live.  In Washoe stories, the Water Babies actually live in all bodies of water, but apparently Cave Rock is their most frequented hangout.  They are very powerful and at times cause illness or even death to people, but can also be positive omens if you approach them carefully and treat them with respect.  It is mostly just the Washoe healers that interact with the Water Babies, though, as most people avoid them by choice.  This is why Cave Rock is always given a wide berth by most of Washoe people as they pass by.

And then there is Ong... The giant man-eating bird who nests in the middle of Lake Tahoe.   He's so strong and powerful that his wings bend the trees along the shore when he flies by.  Actually, legend has it that Ong was killed by a clever Washoe man just before being eaten, but his nest still remains just out of sight below the water surface.

These tales remind me of the Kelpies of England and Scandinavia - you know, those Water Horses with nefarious qualities?  I've blogged about them earlier (Kelpie Blog post link).  There 's no tellin' what'd happen if a Water Baby would jump on a Kelpie and the both of them chance upon Ong, but my thoughts are this is how the Artesians came to be.  Could be wrong, tho...

Finally, on the other side of Nevada (just into Utah) are where the Goshute People reside.  They don't speak of Water Babies, but to them water is just as powerful.  In their language "water" is referred to as a human being - a living entity.  It is described as such because the spirits of all their ancestors live in water.  What a great concept, and once again we see how important water is to humans throughout history. Today's mankind should treat it with more respect - if for no other reason than it contains Water Babies, Kelpies, sacred ancestors, and possibly....even Artesians.

Crystal's Cave - A Watery Beginning

In the Mexican State of Chihuahua there exists the Naica Project - a mining operation principally for lead. The major operation uses huge pumping units to de-water sections of the mine for lead mining. In 1910 within this complex a 250 foot long chamber was discovered which contained beautiful selenite crystals up to 6 feet long - easily the largest and finest gypsum crystals ever found.  In fact, at a depth of about 360 feet, the walls were covered with them.  This site was named the Swords' Cave.

In April of 2000, at 1000 feet below ground level, three more such chambers were discovered. These locations were named the Queen's Eye Cave, Candle's Cave and the most spectacular of them all, Crystal's Cave, where selenite crystals in some cases 30 feet long and as much a 4 feet in diameter are scattered around like common pick-up-sticks.  What has water got to do with this you say?

It's in the formation.  According to the website:

"These macro crystals formed underwater in the area where sulphide saturated phreatic thermal waters (52°C), came in contact with oxygen-rich cold waters, naturally infiltrating from the exterior.  The surface and subsurface waters could not mix due to the density of the phreatic mineralized water; oxygen diffused into the lower layer, resulting in the oxidation of sulphide ions to sulphate which caused an extremely light over-saturation of gypsum and therefore a slow deposit. These singular conditions prevailing for hundreds of thousands of years created a mineral wonderland, a site of scientific interest and an extraordinary phenomenon."

Another amazing story of the wonders of water.  And speaking of water, the clime inside this cave is brutal on humans.  It remains about 45-50 degrees C and close to 100% humidity.  People can only tolerate these conditions for 10-15 minutes at a time normally - and up to about 30 minutes with special clothing and gear.  Kind of sounds like Texas in the Summer, if you ask me!