Please read this link about White-nose syndrome in bats. This is a serious problem that I'm sure everyone would like to help stop.
First and most importantly, about this earthcache, do not enter the sinkholes, caves or any natural formation. Besides being a potential safety risk, foot traffic will accelerate the erosion process.
Karst is a term that was first applied to a plateau region of the Dinaric Alps in Yugoslavia. It is now used to describe similar regions throughout the world that have features formed largely by underground drainage. Karst terrains are characterized by caves, steep valleys, sinkholes, and a general lack of surface streams because drainage is underground. A consequence of this is not only a very interesting landscape (caves have fascinated people for millennia) with unusual habitats for plants and animals, but special problems in water supply, waste disposal, construction, and other land uses.
What does this have to do with Michigan, a land literally scoured by glaciers, a land covered with glacial clay, sand and gravel? Surprisingly, Michigan contains some areas of true karst. They are limited in extent, but this rarity increases their interest and importance. There is also considerable variety in Michigan karst areas: gypsum karst is found in Kent and Iosco counties; a significant amount of surface drainage goes underground in Monroe County, and reappears at "blue holes" in Lake Erie; spectacular sinkholes and earth cracks are found in Alpena and Presque Isle counties; and the broad band of outcrops of the Niagara Escarpment in the Upper Peninsula hosts a number of karst sinks, springs and caves.
The Fiborn Karst Preserve was a limestone quarry from 1905 through 1935. Check out this link for more history of this area.
Today you will learn about sink holes. Sink holes are formed when rock is dissolved away in under ground caverns until the roof of the cavern can no longer support the weight above and collapses. Sometimes a fracture in the rock is widen by acidic water flowing through the soil and into the fractures. Here a roof collapse of rock doesn't occur but just a winding crack that allows the soils above to filter into the openings in the rock. Some sink holes look like a dirt cone in the soil were others have sheer rock walls with broken rock in the bottom. And some are combination's of these two types.
When walking this area stay on the trail. The area has many sinkholes of various sizes. You wouldn't want to fall into any of them. You will be walking to six waypoints, each has a 4" x 4" wooden post with a number on it. At each post you will find a sink hole or blind valley for which you will need to answer a question. Answers to all of the following questions should be determined by standing at the 4" x 4" wooden post. Please do not walk into any geological feature. To log your find please email the cache owner the answers to the following questions:
Posted waypoint – Trailhead: N46 12.535 W85 10.856 The MKC believes that the swamp to the south once covered this area. Beaver activity may have assisted by raising the swamp's level. The water began to dissolve the joints in the limestone bedrock. Finding it’s way underground to the South Fork of the Hendrie River about a mile to the northeast.
What is the elevation that your GPS reads?
A2 – Shallow sinkholes or “Solution Pans”: N46 12.537 W85 10.880 The many shallow sinkholes may be an example of early karst development. The water source that started these sinkholes have been diverted else where causing the development of these sinks to slow or even stop.
Without moving how many sinkholes can you see?
A3 – Flat Creek Sinkhole: N46 12.548 W85 10.927 Flat Creek flows north from the swamp and goes underground here. The creek is most likely natural but some areas appear to have been dug deep to aid in the drain of the land for the quarrying of the limestone. The Flat Creek and its sinkhole are typical of the early stages of cave development in the area.
In your opinion, what is the maximum depth of this sinkhole?
A4 – Cone Sink: N46 12.560 W85 10.960 This sinkhole is an example of the collapse of a cave roof below. Sand is working its way through the collapse and is being washed downstream inside the cave. The Flat Creek is most likely the water source for this cave. The reduced flow of the Flat Creek has slowed the washing away of sand.
In your opinion, what is the maximum depth and width of this sinkhole?
A5 – Brushy Sink: N46 12.545 W85 11.001 Water that pooled upon the limestone will form a network of streams until one of the streams becomes large enough to carry all available water. Many small sinks will form until that happens. This area is similar to the Flat Creek area, just less developed.
In your opinion, what is the maximum width of this sinkhole?
A6 – Bog Creek and Reluctant Sink: N46 12.522 W85 11.049 The surface drainage became better organized at some point in the past forming a single surface stream. Cutting a small canyon into the limestone ending in a blind valley sinkhole. The sinkhole was name “Reluctant” because early explorers hoped it would lead to a cave, but it was to narrow and filled with sediments.
In your opinion, what is the maximum depth and width of this small canyon?
Not required but always a pleasure to see, please post your photographs too.
To email your answers please click here to open a new email.
This cache is located within the Fiborn Preserve, which is owned and managed by the Michigan Karst Conservancy. All of the preserves managed by the MKC are free to visit. Parking is allowed only in the designated areas. Always practice Cache In, Trash Out.