Visit Forestville/Mystery Cave State Park to see natural wonders above and below ground. In the summer, beat the heat with a visit below ground. Explore the world of Mystery Cave with its stalactites, stalagmites, and underground pools. Park naturalists provide tours of the cave throughout the summer and on weekends in the spring and fall.
Learn more about Mystery Cave Tours.
Mystery Cave Tours
Discovered in 1937, Mystery Cave is the longest cave in Minnesota - spanning over 13 miles underground. It is a network of passages that was dissolved by moving water. On the tours, you will travel the subterranean paths this water has taken, seeing many of the features that make up Mystery Cave including stalactites, stalagmites, flowstone, fossils, and beautiful underground pools. Parks naturalists lead your tour through various portions of the cave and explain its history, its features, and how it was formed. The cave temperature is a constant 48 degrees F. Warm dress is recommended.
Southeastern Minnesota is cave country. Wherever limestone and dolomite make up part of the bedrock, caves are likely to be found because those rock types are susceptible to extensive solution activity by groundwater. Fillmore and Olmsted counties contain the majority of caves in Minnesota. Most of the natural cavities are found in limestone are of the Ordovician Dubuque and Galena formations.
Limestone caves develop best near the water table, the boundary between saturated and nonsatureated rock and soil. Water moving down to the water table becomes more chemically active as it picks up carbon dioxide from decaying organic matter in the soil. The resulting mild carbonic acid dissolves calcite, the mineral found in limestone. When this mixture reaches the water table another chemical process occurs due to the slightly different acidity of the water table. The co-mingling of the two waters, water from above and the water table, renew the chemical energy to dissolve additional limestone.
Creating caves occurs along pathways, called fracture zones, with in the rock that allows the greatest volume of water to flow. The location and direction of the bedrock determines the occurrence and shape of caves. Another important factor is the outlet for water discharge. Deeply incised valleys allow the water to drain allowing more fresh water to enter, thus continuing the creation of the caves.
As long as the cave remains full of water, it continues to be enlarged by the water/solution activities. When the water table drains and the cave fills with air, another state in development begins, the creation of "cave decorations".
The State Park Naturalists will provide additional routine information needed to answer the questions required for completing this earthcache. All tours require a fee based upon age and tour, and start at the visitor's center.
Tour options:
- Scenic Tour: This popular one hour guided tour provides the best overall cave experience. You'll see excellent examples of cave mineral deposits, along with the pools and long linear corridors that are typical for Mystery Cave and Turquoise Lake. Many formations are actively dripping. These features are illuminated with dramatic lighting that accents the cave in light and shadow. This stroller and wheelchair accessible tour involves 3/4 mile of walking on modern paved trails and metal bridges.
- Flashlight Tour: A rugged experience. See a portion of the cave by flashlight.
- Geology Tour: A two-hour rugged, flashlight experience with a focus on cave geology.
Mystery Cave questions:
Scenic Tour:
- In the first passageway, the guide should point out a unique fossil, what is this fossil?
- In the second passageway there is a room with distinctive dome shaped holes in the ceiling. What are the dome-shaped openings called?
- The formations are created during floods, how does the water enter the cave during floods?
- How does the water create these unique features?
- What creates the beautiful color of Turquoise Lake?
Flashlight and Geology Tour:
- Observe the raft cones in Blue Lake, calcite precipitates on the water surface, making a crust or calcite rafts. Describe how the cones are created from the rafts.
- How are worm burrows created?
- The Stewartville formation contains what type of holes? Describe the difference in appearance between Dubuque and Stewartville limestone.
- Dubuque characteristics:
- Stewartville characteristics:
Email your answers via my profile. Please include the earthcache name Mystery Cave the tour you choose number in your party and cachers names. One email per caching group.