ROCKHOUNDING AND ADVENTURE TRIPS: Michigan Karst Cave Information – January 2009

NOTE: The following information was taken from the Michigan Karst Conservancy web page. Contact information is at the end of this article.

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 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 Losco 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.

Each of these areas is in some ways unique to the geology of Michigan. Some sites could be considered of national significance. Yet, today, most of these areas are subject to the possibility of incompatible or damaging use. They are also mostly on private land and most may not be visited by the public. Protection and awareness of these features, and their potential for educational and scientific uses, is what the Michigan Karst Conservancy (MKC) is all about.

Our Purpose

The Michigan Karst Conservancy is dedicated to the preservation of examples of Michigan’s karst areas. It was formed in 1983 by people with an appreciation for Michigan karst features, when it became apparent that no other groups were interested and able to actively protect such areas for their inherent geological interest.

The purposes of the Conservancy are the acquisition, management and protection of the finest examples in Michigan of karst areas and features, as well as scientific study, and conservation education regarding karst.

There is only a finite time within which to establish protection for the most significant areas. Indiscriminate use of sinkholes in Alpena County as dumps and landfills is still occurring, which results in groundwater pollution and degrades and obscures these fascinating features. Many sinkholes have also been filled in for farming. In the Upper Peninsula, one large and several small caves have been quarried away (in a State with very few caves and in a situation where the caves could have been preserved with negligible cost or trouble). In other areas, erosion damage is occurring due to uncontrolled foot and vehicle traffic.

Risks of further loss of the relatively few remaining significant features by activities that would not preserve them are very great. It is, in fact, the small sizes of the remaining significant karst areas that make them an opportunity for preservation. Because the areas are small, it is possible to acquire the land and hold it in trust for informed public use.

The MKC now owns two preserves. The 480 acre Fiborn Karst Preserve in Michigan’s upper peninsula, purchased in 1987, includes an extensive and nearly complete karst drainage system with features such as sinkholes, caves and disappearing streams. The 31 acre Stevens Twin Sinks Preserve west of Alpena, purchased in 1990 and enlarged in 1996 by the donation of the 2.5 acre Bruski Sink, contains examples of sinkhole habitats unique to that area. Scientific research and educational programs are conducted at both preserves. Additional information about these preserves and about visiting them may be obtained by contacting the MKC at the address below.

How Can You help?

The MKC is the only land trust group in Michigan dedicated solely to preservation of examples of Michigan’s unique geology and associated ecosystems. Like other similar groups involved in plant, animal, and habitat protection, the MKC receives no government support, but relies solely on YOU, the public, for its funding. One way to support the MKC is by becoming a member. Dues finance the operating costs of the MKC, and many members volunteer their time in the work of the Conservancy. Members receive a regular newsletter and notices of meetings and programs. All except Student and Institutional Members may hold office and chair committees. All except Student Members may vote to elect the Board of Trustees, the governing body of the MKC.

However, the preservation work of the MKC is based upon donations for buying lands and managing their features for appreciation, protection and study. The MKC accepts donations in many forms: you may wish to donate cash, possibly a gift of land suitable for preservation, or land or securities that may be sold to finance the MKC’s preservation activities. We need your help to preserve Michigan’s karst lands. The future of the natural history of Michigan will be enriched by your generosity.

Michigan Cave Information

It doesn’t seem likely that there would be caves in Michigan, but there is! Caves are few in our state but not unknown in the region. In fact, Michigan caves have some interesting history associated with them. A cave is formed by water seeping in the cracks of limestone bedrock. Water in the soil picks up carbonic acid that eats up softer layers of limestone it passes through. After countless years the water creates sinkholes, underground streams and caves. This combination of formations is called “karst” terrain and can be found in the Great Lakes region due to a geologic formation called the “Niagara Escarpment”.

The Niagara Escarpment is the edge of a thick series of dolomite limestone layers. The rocks are resistant to erosion and stand as a prominent line of bluffs. The ridge runs around the west side of Lake Michigan north into Door County, Wisconsin, over to the Garden Peninsula of Michigan’s Upper Peninsula, to Mackinaw, Drummond, and Manitoulin Island, then the Bruce Peninsula in Ontario Canada. From there the Escarpment goes southeast across Ontario and into New York, where it creates the Niagara Falls. It’s along this escarpment where many caves can be found.

Although every Michigan cave claims to be the only one, there are a number of them, some of which are open to the public. Bear Cave, downstate in Buchanan, is open to the public. It is not a karst cave, but a much rarer “tufa” cave. It has stalactites, flowstone, petrified leaves, and other strange shapes, all colored by metal oxides. In 1875, the loot from an Ohio bank robbery was hidden in this cave. Inspired by this event, it was featured in the 1903 movie The Great Train Robbery that is now considered a silent film classic. The cave is entered through the gift shop.

Skull Cave on Mackinac Island is a karst type of cave found on the Niagara Escarpment. According to tradition, this is the cave in which the English fur-trader Alexander Henry hid during the Indian uprising of 1763. He claimed the floor of the cave was covered with human bones. Possibly it was once used as an Indian burial.

Burnt Bluff Cave, AKA Spider Cave, in Delta County (in the U.P.), has some Indian pictographs (rock drawings) associated with it. This site is located on private property, and the pictographs appear at the base of a 140 foot limestone cliff on Big Bay De Noc. The small cave is thought to have been used in some ritual. Over 100 projectile points were discovered in Spider Cave, all with broken tips, suggesting they were thrown into the cave.

The 480 acre Fiborn Karst Preserve in Michigan’s Upper Peninsula, is owned by the Michigan Karst Conservancy. It includes an extensive karst drainage system with features such as sinkholes, caves and disappearing streams.

In eastern Alpena & Presque Isle Counties, exposed limestone bedrock is common and karst depressions or sink holes can be found in the Rockport area. The 31 acre Stevens Twin Sinks Preserve west of Alpena, purchased in 1990 by the MKC, contains examples of sinkhole habitats.

There are also underwater “caves” in the lakes. The Alger Underwater Preserve offers two main diving attractions: shipwrecks and sea “caves”. The sea caves are portions of underwater sandstone cliffs where the softer sandstone has been eroded away by waves. Other “sea caves” are found along the Pictured Rocks National Lakeshore. The caves are found in water 20 feet deep or less. The Thumb Area Underwater Preserve has caves created by eroded limestone. The caves are located near the edge of the reef near Port Austin Lighthouse.

Unbelievable as it may be, there is a group of islands in the Great Lakes that aren’t from this world. The Slate Islands near the top of Lake Superior, south of Terrace Bay Ontario, are seventeen islands that many scientists believe to be the product of an impact crater. A staff scientist at NASA’s Lunar and Planetary Institute claims the meteor that created the Slate Islands was about 20 miles in diameter. Studies indicate that the asteroid entered 2 miles deep inside the earth and has a 30′ wide shatter cone. Shatter cones are found around sites of nuclear explosions but are only about an inch deep. The shatter cone on Slate Island maybe the worlds largest! Traveling at up to 12 miles per second, it vaporized in a blast equal to more than one million tons of TNT. The atomic bomb dropped on Hiroshima generated the amount of energy of only 15 thousand tons of TNT.

The size and speed of this asteroid puts it in the category of a “dinosaur killer”. Popular dinosaur extinction theories claim that the impact of a large asteroid caused a “nuclear winter” that wiped out most of the life on earth and caused the extinction of the dinosaurs. The theory claims that a single high velocity asteroid impact in an area now covered by the Gulf of Mexico was to blame. Estimates of the age of the Slate Island crater range from 350-450 million years old and the mass extinction of the dinosaurs is thought to have occurred around 65 million years ago. Given these age estimates, the Slate Island event happened well before the age of the dinosaurs (claimed to have begun around 200 million years ago).

Mackinac Co., Michigan
Michigan Karst Conservancy – Project No. 1

The Fiborn Karst Preserve, a property of the Michigan Karst Conservancy (MKC), was created in 1987 to protect and manage the unique natural features of the area, which include extensive outcrops of limestone, the longest known cave in Michigan and its associated streams and sinks, and the plants and animals that occupy a variety of marsh, woodland and cave habitats. The preserve is managed as a natural area and is available to the public for scientific study, educational programs, and nature appreciation activities that cause no damage to its features. Two interpretive nature trails with trail guides commence at the Emma Kalnbach Pavilion area.


The limestone outcrops and caves were identified as a potential economic resource in 1898 by Chase S. Osborn (1860-1949), editor, prospector, writer and politician (Governor of Michigan, 1911-12), who, with William F. Fitch (1839-1915), general manager of the Duluth, South Shore and Atlantic Railroad (1888-1911), bought the land and opened the quarry in 1905. The name Fiborn combines the names of Fitch and Osborn. The land and quarry were purchased by Algoma Steel Co. in 1909. The village of Fiborn Quarry existed between 1905 and 1936, when the quarry closed. Remnants include a number of foundations. Historical records of the village and quarry operations, and early descriptions of the caves, have been partially collected by the MKC in its ongoing Fiborn History Project. A display of historical documents and photographs is now located at the Emma Kalnbach Pavilion at the Preserve.

The first known studies of the caves were in 1901 by Michigan State Geologist A. C. Lane, who mapped and described one of the caves and numerous openings and other surface features that existed prior to being quarried away. Beginning in 1975, the Michigan Interlakes Grotto (MIG), a chapter of the National Speleological Society, mapped the remaining caves and conducted hydrological and biological studies. At the same time, the caves became more widely known and more heavily visited. Increasing vandalism and concern for their future led eventually to the incorporation of the Michigan Karst Conservancy in 1983, and the purchase of the land in 1987.


The Preserve is on a portion of the Niagara Escarpment – a band of resistant outcrops (mostly dolomite) of Silurian age that form prominent hills from the Door Peninsula in Wisconsin to Niagara Falls (and beyond). The escarpment is subdued here, but the limestone is close to the surface and drops off quickly further north. The quarry is in the Fiborn Limestone member (type locality) of the Hendricks Dolomite (Burnt Bluff Group). An extensive swamp to the south is “perched” on the escarpment at this point – aided by the activity of beavers. The South Fork of the Hendrie River is cut into alluvial deposits to the east and north, forming a local base level.

The caves formed by ponded water from the swamp dissolving joints and bedding planes in the limestone between the levels of the swamp and river. Most of the cave enlargement probably occurred following the fall of the post-glacial Lake Algonquin, about 10,000 years before the present, which had earlier covered most of Mackinac and Chippewa counties. There are ancient sand dunes and shore features in the area.

Water from the swamp currently goes underground at several sinks located over a distance of about 2.0 kilometers east-west, and resurges at a spring along the river (not in the Preserve).

The longest cave in the Preserve (620 meters) is Hendrie River Water Cave. It carries about half of the karst drainage from the swamp. The stream flows north in the cave, against the dip (which is ca.8 m./km. to the south), over a 3 meter waterfall formed on a resistant dolomite stratum, and disappears into a sump. The stream then turns east and flows 1.6 km. to its resurgence. The cave below the waterfall floods after heavy rains.

Opportunities exist in the Preserve for studies in stratigraphy, hydrology, water chemistry, sedimentology, speleogenesis etc. Proposals for such research are invited from institutions and individuals.


The Fiborn Karst Preserve is managed by the Fiborn Karst Preserve Committee of the MKC.

It is the purpose of the MKC to manage and protect karst areas for scientific study and conservation education. These purposes are implemented by making MKC Preserves available, without charge, for public uses that are compatible with long-term preservation. Protection of natural features of a Preserve, and the safety of visitors, are major concerns. For these reasons the following policies have been adopted for the use of the Fiborn Karst Preserve:

The preserve is open to the public, except as noted below:

  1. The following are not permitted in the preserve: fires, camping, littering or dumping, alteration of any natural features, collecting of firewood, vehicle use off-road. firearm use except during firearm hunting season, trapping, or pollution of soils or streams.
  2. Permission from the Preserve Committee is required for climbing or cave exploring, scientific collecting (of minerals, flora or fauna), excavation or movement of soil or rocks, and installation of instrumentation.
  3. Climbing and cave exploration in the Preserve are permitted only if an experienced climber or caver (as determined by the Preserve Committee) accompanies each group, and a liability release and acknowledgement of the Preserve Use Policies is signed by every visitor.

The Preserve is available for both research and recreation by interested persons and groups. Classroom projects, theses, individual growth experiences, nature study and appreciation, photography, and art work, are all activities that are encouraged by the MKC, so long as they are conducted in a manner to protect the natural features of the Preserve.

The work of the Michigan Karst Conservancy is carried out by volunteers, who believe in the value to the public of protecting examples of karst features in Michigan for educational and scientific uses. Donations to the MKC are tax deductible in accord with federal law. For further information about the MKC, and membership in it, write:

Michigan Karst Conservancy
2805 Gladstone Avenue
Ann Arbor, MI 48104
E-Mail mkc @

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