Hale Lake is a really interesting karst feature that is somewhat anomalous, or stand-alone in this local area - the next closest karst features that we know of are Blue Lake Sinkhole on Gavilan Ridge, the Eagle Dry Lakes along the Eagle Creek drainge, and Fort Stanton Cave. The word "karst" is German for a geological area where the rock tends to be soluble, such as gypsum or limestone, in which caves can form. The limestone here is the San Andres and it's Permian in age, about 267 million years old. The sink is either a dormant sinkhole or a large subsidence feature. Actually, there's not really any such a thing as a dormant sinkhole. At the moment, this one seems shallow and holds water, which is due to montmorillinite clay - a tactic by ranchers and others to seal cattle tanks, so water will stay on the surface. Eventually though, there could be geologic action that would make the sink more active.
Hale Lake Sinkhole Karst Feature, as sinkholes go, indicates a void somewhere below, where limestone layers have collapsed, or stoped, up to the current surface to form the sink. With any luck, the void below will turn out to be the Fort Stanton-Snowy River Cave System - there are passages at the far southwest end of Snowy River Passage that split off and are headed south for Eagle Dry Lakes subsidence features on Eagle Creek, which are as large or larger than Hale Lake. If the passages keep trending south, Hale Lake is kind of in line. Already, at 12 miles long, Snowy River Passage is the longest cave passage in the world; the cave overall is 42.345 miles, longer, now, in linear surveyed distance, than Carlsbad Caverns. At the current end-of-survey station, the Snowy Passage is large enough to hold a large office building - it is a big cave system, in volume and length.
Hale Lake Sinkhole is about 12 miles south-southeast of current end-of-survey. So far, there's only one known entrance for the cave - back near Fort Stanton, and it takes about 8 hours for project cavers to get to base camp at Midnight Junction out near those break-away passages. If those passages are below this location, it will make Fort Stanton Cave one of the longest caves worldwide. A drawback - just to get to Midnight Junction - that's among the most remote places on Earth that humans have ventured...any cavers out there might as well be on Mars...!
My fellow cavers and I are doing a geophysical technique called resistivity that can show anomalies - voids - below. Preliminary work shows a series of anomalies from Hale Lake to the north that may be cave passage and they are trending back in the direction of Fort Stanton Cave! Keep your fingers crossed (and sure wish we could find another entrance). If Snowy River is below, even if it's not, whatever is below is likely at a relative similar depth, probably 600-700 feet below.
One thing really critical about your pending visit - if it's been raining, and FR 443 is wet, stay way away - do not go on a wet FR 443, and certainly not into the subsidence basin, because the clay there will cause your wheels to hopelessly spin. And the only way you're getting out is waiting until it dries. But more likely than not, you're walking out, unless you have camping time on your hands. If you bring OHVs, you are required to keep motorized vehicles on designated routes; no off road travel is permitted. Motor vehicle use maps are available for free at the Smokey Bear Ranger District office; 901 Mechem in Ruidoso.
To learn all about Fort Stanton Cave, the amazing Snowy River Passage and caving in general, please visit the Fort Stanton Historic Site Visitor Center. The non-profit Fort Stanton Cave Study Project and Bureau of Land Management, Roswell Field Office have created a beautiful exhibit. The site is open daily, Thursday-Monday, 10:00 AM to 12 Noon, and 1:00-4:00 PM (there's also a geocache there - Hardtack & Coffee GC76CF2. , and about 100 other caches on public land within 3 miles around the fort. Further, if there's a soldier on duty, wearing a circa 1858 uniform, it's likely Private Bilbo).
So, let's see what you've learned. You know the deal - don't post your answers here. You gotta email, or use geocaching's messaging system, to send your answers to the brilliant, handsome, exceptionally outstanding, caver-type cache owner who put this Earth Cache together. #1 is required:
1. Please describe what this place looks like from the Hale Lake Sinkhole Earth Cache coordinates. It is a specific scene and you can optionally send me a sketch or photo.
Now, try for 4 more answers but if you get them all, you'd probably make for a good caver:
2. Have you ever been to a sinkhole before? If so, where was it, and did it have a name?
3. What is Midnight Junction and how long does it take cavers to get there?
4. What might be a significant aspect of this sink in relation to Fort Stanton Cave?
5. What do you think constitutes the edges of this sink?
6. Why would you not want to be at Hale Lake Sinkhole during wet weather?
7. What can resistivity do?
8. What's karst?
Permission to establish this cache was given by Christina M. Thompson, Recreation/Lands/Minerals Staff Officer, U.S. Forest Service, Lincoln National Forest, Smokey Bear Ranger District, p: 575-630-3050; f: 575-257-6174, 901 Mechem Drive, Ruidoso, NM 88312