SOMETHING ABOUT CAVES in MICHIGAN How Caves and Sinks Are Formed
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when it reaches limestone it is ready to dissolve the rock. SOMETHING ABOUT CAVES in MICHIGAN How caves and sinks are formed. Limestone is a rock made of layers upon layers (or by strata) of lime muds and shells deposited in ancient Helen M. Martin seas. Water was squeezed out or evaporated from the muds and they became rock. This compaction caused Illustrated by James Campbell vertical cracks, or joints, in the layers. Some of the Geological Survey Division limestones are ancient buried coral reefs and are Department of Conservation porous. So that water entering the cracks and pores has Lansing, Michigan a large surface to work upon to dissolve. Slowly water 1958 works down a crack in the limestone dissolving the rock and making the crack wider, it spreads in the horizontal DO WE HAVE CAVES IN MICHIGAN? Probably. Do cracks, or bedding planes, dissolving as it seeps along, we have caverns in Michigan? Perhaps. Like the and in time the openings are large enough to be caves Mammoth Cave in Kentucky? Who knows? The and galleries connecting them. Large and numerous spelunkers, speleologists, the cave explorers will need to caves connected with galleries of great or unknown sift the surface indications and explore. extent are called caverns. Some large caverns have What are the indications? Caves and caverns are been made by water from warm underground springs. excavations, made by nature in rock below the surface In many caves the roof blocks of limestone are eroded or of the land. Water is the agent, the tool used. Rocks are loosened and fall to the cave floor so that in time the can be dissolved by slightly acid water but limestones, thin unsupported roof falls in and a sink hole results. dolomites and gypsum can be dissolved most readily. Water seeks the lowest level, so rivers are in caves and Rain water falling through the air takes up carbon caverns, and flow underground in the horizontal cracks dioxide and becomes slightly acid. As it percolates in limestones. through the soil it becomes more acid so that if and In her eternal changing of the earth Nature by cracking, Something About Caves – Page 1 of 3 cutting, carving, dissolving, makes holes in rock and water by opening of communication with underground then proceeds to fill them. In limestone rocks most of channels. Big Sink and Little Sink in the south half of the filling material is the principal mineral of the lime Sec. 2, Whiteford Township, have been filled with water muds, calcite. and are one lake in the spring, but cornfields in the fall when the water drained downward. Perhaps the water Slowly evaporating lime-saturated water deposits was held up in the spring by an ice plug. Fish come up crystals of calcite and of some other minerals in smaller Halfway Creek and inhabit the lakes for a time." Do they amounts in the cracks of the rock making veins of return underground to Lake Erie? Many sinks known to crystal. The water that drips through a crack deposits a the early settlers in the county are now plugged and ring of calcite around the opening. As it continues to drip filled making valuable truck farm land. Caves they knew ring after ring is deposited building a cylindrical conical are now sinks and quarrying has destroyed other caves deposit from the roof of the cave or cavern. This is a as well as sinks. Probably a series of underground stalactite. Water that drops from the building stalactite caves and connecting galleries of no great dimensions splashes to the floor, there evaporates, deposits its underly this part of Monroe County. mineral, and builds up a mound called a stalagmite. When stalactite and stalagmite meet a column is formed. In 1860 Alexander Winchell reported finding sinkholes In many caves stalactites forming along a joint build a along the north line of Bay County. He stated the sinks curtain or drapery-like mass of crystal pendant from the were caused by solution of the gypsum beds in the area cavern roof. The fantastic and beautiful formations of and caving of the overlying thin limestone. caves and caverns are the monuments of moving water, In 1869 Newton Winchell, brother of State Geologist which first dissolved limestone and/or gypsum rock, then Alexander Winchell, in field notes describes Sunken evaporated and redeposited the minerals in crystal form, Lake in Sec. 32, T33N, R6E, Presque Isle County. At leaving many impurities to give color. that time the North Branch (of Thunder Bay River) Not all caves are in limestone. Many have been carved entered the lake from the north and at the time of high in the rocks along the sea or Great Lakes coast by the water "flowed out a little east of midway” but for most of pounding and undercutting of wave tossed rocks on the year the lake had no surface outlet "the water cliffed shores. Along Lake Superior caves or recesses entirely disappearing at the west end of the lake under a have been cut in the sandstones of the Pictured Rocks, ledge of limestone, entering about 85 feet below the some in the cliffed shores of the black rocks north of level of the surrounding country and in the deepest part Marquette. But these caves have wide entrances and of the lake bed." Lumbermen threw tons of logs, brush, are not deeply recessed in the rock nor are their floors rock, dirt into the mouth of the subterranean passage to much if at all below lake level. On Mackinac Island prevent escape and later built a dam to divert the river several caves were made by the higher-level ancestral from Sunken Lake so that logs might be floated. Great Lakes pounding on the limestone shores and cliffs Most of the bed rock of northern Alpena, northern Mount and eating into the cracks of the limestones of the Morency, and northern Otsego and Cheboygan counties islands. is limestone with a thin covering of glacial drift. In this But what about the speleologists dream of caves in area are shallow and deep sinks and deep circular lakes, Michigan? Several, of the rock bowls that are in the such as the Devils Soup Bowl in Otsego. foundations of Michigan are limestones and/or Many sinks are reported in the northern townships of dolomites. Where they come to the surface (under Alpena County. Many are from forty to seventy feet glacial drift in most areas) is shown on the map. deep. Two of them are but five feet apart. The wide Early settlers in Monroe County reported curious depression northward from Lachine is a huge shallow underground rumblings especially in the spring and after sink several miles wide. Parts of Long Lake basin heavy rains and they found many rock openings into probably originated as several united sinks into which an which surface water swirled like a whirlpool into underground river probably flows. In 1876 Karl underground passageways in the limestone. In his field, Rominger, then State Geologist, noted a peculiar notes for October, 1838, Bela Hubbard, Geologist, on phenomena at the outlet of Long Lake. A peculiar 3- the first Geological Survey describes many sink holes in armed lake-filled basin probably formed by solution and Whiteford Township. Ottawa Lake in a large "sink" was settling along joint cracks, was named Devils Lake. "In then nearly dry, other sinks were also dry, although spring and early summer the outflow from Long Lake is ordinarily nearly filled with water. Hubbard wrote "These large and then Devils Lake depression becomes a lake "sink" derive their name from the reputed fact of their and its overflow passes into Lake Huron via Long Lake becoming a collect for the neighboring waters which are Creek. But in the late summer when Long Lake is low, here absorbed. They are said to have no outlets. Devils Lake becomes dry and the Long Lake outlet is a When the larger sink is filled with water a whirlpool may funnel shaped depression in the south area leading to an be observed of sufficient force to draw in rails thrown underground channel to Lake Huron.” The deep parts of from a distance which disappear into some cavity below El Cajon or Misery Bay over which the water never . .” freezes is a sink 76 feet deep. The springs bubbling into it may be outlet from Long Lake. The cliffs at the head Many rock wells in the county when deepened lost all of Misery Bay are the walls of an ancient sink hole. Something About Caves – Page 2 of 3 The Little Ocqueoc River in Presque Isle County flows, everwidening cracks in the limestone in Sec. 6 T32N, part of its distance underground. Once it was an entirely R8E, Alpena Township. The owner of the property "Disappearing River,” but now the roof of much of its stated that the cracks at first were large enough for a underground tunnel has fallen in so that the river can be chicken to fall in, but by 1950 they were wide enough for seen or heard beneath the blocks of limestone. The a heifer to fall in and so deep that snow and ice did not Shoepac Lake area of southwestern Presque Isle melt from them until late summer and a man could go County is a famous area of sink holes. Shoepac Lake is down 11 to 20 feet below the surface. 18- to 20-feet deep but 500 feet from its eastern shore is Not until the summer of 1957 did the spelunkers dream a sink 120 feet deep, with no water in it and tall pine come true under Walter Grocholski’s farm, Section 28, in trees growing on the floor and sides of the sink, 90 feet Presque Isle Township.