The cavern is more than one-half mile long, and visitors will walk up and down 448 stairs one way – 896 round trip – as they visit the nine separate “rooms” or chambers. The largest of these chambers, the ballroom, measures more than 300 feet across and 90 feet high.
The process that started the formation of Minnetonka Cave began when the sediments that formed the limestone beds of the cave were deposited, about 340 million years ago, in an ancestral tropical sea thought to have been situated near the present-day Idaho-Oregon state line.
Over hundreds of millions of years, many tremendous forces with the earth have been at work. Probably the most notable force was the raising of the limestone, once at sea level, to its current 7,700 feet, which is the elevation of the entrance to the cave. The limestone bed has shifted from its original position due to the power of plate tectonics which, over time, shifts entire continents.
The process of forming a limestone cave is called “solution development.” As the water from rain and melting snow enters the ground, it absorbs carbon dioxide from the air and decaying plant materials. Carbon dioxide in the water makes an effective solution for dissolving limestone. This solution travels along cracks in the limestone caused by the earthquakes and settling.
Over many thousands of years, where there was once only a crack, a cave was formed. If not for all the cracks, faults, and fissures in the limestone, Minnetonka Cave would never have been.
River beds can be seen at two different places in the cave; the first spot is near the front of the cave and the second is near the back. It is estimated that two thousand years ago, an earthquake caused much of the ceiling of the cave to fall into the river bed. The reason the climb through the cave is so steep is because it is necessary to climb up and down several debris piles which fell from the ceiling during that earthquake.
Beautiful formations which grow in limestone caves are the primary reason people visit these caves. Minnetonka Cave has eight of the approximately 15 types of limestone cave formations. Another attraction to visitors is the many different kinds of fossils found throughout the cave.
Over 22,000 visitors make the hike each year, many of whom come away with the memory of a remarkable walk into one of the earth’s most beautiful creations.
Formations Found Within the cave
Harboring eight of the approximately 15 types of limestone cave formations, Minnetonka Cave is a wondrous geological journey.
Stalactites grow like icicles from the ceiling of limestone caves. When the stalactites begin their formation, they are little hollow tubes, often called soda straws. One of the ceilings in Minnetonka Cave is named “The Soda Straw Ceiling” because hundreds of these little formations can be seen. The most striking stalactite in the cave is called “the Bride;” she is over eight feet long with a diameter of nearly 18 inches. The lacy and ruffly formation of her exterior prompted the naming of this stalactite.
Water dripping from the ceiling forms stalagmites which grow from the ground up. The three largest formations in the cave grow side by side and are named “The Three Sisters.” Two of the three are over 10 feet high with diameters of nearly four feet at their base. Another large stalagmite was formed from the water dripping from “The Bride.” These two formations, “The Bride” and “The Groom,” grow in “The Wedding Room.” The wedding will occur when the formations grow enough to join together.
Columns or pillars are formations which grow the entire distance from ceiling to floor. There are three ways in which these formations are created – stalactites may grow long enough to reach the floor, stalagmites may grow high enough to reach the ceiling, or stalactites and stalagmites may join.
Drapery are formed when water runs down the side of a cavern forming a leading edge which the water continues to follow, thus causing the formation to grow. The largest pieces of drapery in the cave are over 20 feet long and over one foot wide.
Flowstone is formed when water comes through the ceiling and flows over the rocks. One large rock in the cave that is completely covered is shaped like a grasshopper, another is in the shape of golden coins stacked in piles, hence the name “The Treasure Room,” and one that has formed on the side of the cave is called “The Frozen Waterfall” because it resembles ice.
Cave coral is very common in Minnetonka Cave. How cave coral forms isn't entirely understood, but it is seen in many places throughout the cave. It resembles either ocean coral or popcorn. In fact, one formation in the cave has such a beautiful caramel color that is is aptly named “The Caramel Corn Point.”
Helictites are some of the strangest and most unusual formations found in limestone. They grow in many different grotesque shapes. One formation in the cave has grown into two distinct branches and is called “The Devil’s Fork.” Several others appear to defy gravity by turning upward and growing back toward the ceiling.
Rim stone is found in the back portion of the cave and is not open to the public. Pools of water are encircled by rims of calcium carbonate. The water in these is so clear as to be almost invisible.
The last formation found in the cave in a very limited amount is formed from mineral aragonite. Aragonite grows in formations called Anthodites. These are the stone flowers of the cave. Hair-like crystals radiate from a central point making little blooms of crystals on the wall or ceiling.
Discovery and Development of the cave
In 1907 or 1908, Edward Arnell of St. Charles was looking for timber. As he walked, he flushed and shot a grouse which fell near the cave entrance. The opening was covered with rocks and brush and the discovery was made only by a cool breeze blowing from within the cave.
Arnell returned to where he and others were constructing a sawmill and the next day, he and a group of seven others explored the cave. They pried the rocks away from the opening and, with lanterns and torches, explored a part of the cave.
Later, explorations revealed the skull and bones of a large bear near the front of the cave. Also found were a live porcupine and the skeletons of several others, hence the cavern’s first name, “Porcupine Cave.”
Roy Welker, educator and church leader, first applied the name “Minnetonka,” an Indian name which means “falling waters,” suggestive of the water dripping from the ceiling of the cave. As any visitor soon discovers, this is a very fitting name.
Considerable vandalism mutilated or destroyed many of the more striking and beautiful formations in the cave from its discovery until about 1939. During that period, very little public interest was shown toward the cave and only small groups visited it to satisfy curiosity.
From 1939-1940, the World Progression Administration constructed a trail from the canyon road to the cave entrance, widened the entrance, and installed interior paths, steps, and railings. Other improvements were made throughout the years as different organizations were placed in charge of the care and upkeep of the cave. In 1947, the Forest Service reopened the cave which had been closed during WWII.
The Paris Lions Club was issued a special permit to operate the cave until 1963, and in 1964 the Forest Service again took over management of the cave. In 1963, electrical lights were installed which put an end to visitors having to carry their own lanterns or flashlights. In 1990, a new electrical system was added to make the cavern even more beautiful. Student athletes from Bear Lake High School helped install new railings in 1993 to make the cave safer for those needing help walking up and down the numerous stairs.