Crystal Cave Exploration

Our Field trip

We began our trip by looking at a sinkhole behind the gift shop. This was a previous room in the cave itself which collapsed forming a sinkhole in 1982. This room, called the Cathedral Room, actually was a fallout shelter full of supplies during the era where there were threats of nuclear war. Many sinkholes are present in this area forming a line from north to south extending in a line down to the Mississippi River.

The rocks on the second level are from the Prairie Du Chien Group in the Ordovian Era. This era occurred 480-485 million years ago. The three different rock formations in the caves are the New Richmond, Oneota, and Shakopee. This rock group was rich with iron ore and makes up the rock layers that form the bluffs of the Mississippi River. Many quartz crystals are found in small pockets of the cave.

Refrigerator Room

This is the coolest room in the cave. It stays a consistent 9 °C (48 °F) all year round. There is an elevated amount of radon in this room, as well; however, it is not as much as you can be exposed to in a basement. The air is recycled throughout the cave. Warm air at the top of the cave starts to cool and begins to drop to the lower levels. Eventually, this cooler air exits through the back of the cave. This process is reversed during the winter time.

Ball Room

The dip at the entrance of the Ballroom was the lowest point in the cave which is 21 meters (70 feet) below the surface. This is the largest room in the cave able to hold enough people for a wedding which actually occurred. This is where we found the highest concentration of bats throughout the cave system. This room is also believed to be one of the entrances used by the bats to get into the cave system.

Wish Room

This is the room where the most iron ore was extracted. The walls are soft enough to be able to place coins in because over time the iron ore has been broken down to the mineral level and turned into iolite, a form of clay.. Over the years placing these coins on the walls became a tradition. The theory goes that if the coin you placed in the wall still remains, your wish will come true. A fascinating thing about this room involves the use of a black light. It is passed over the rocks and then when the lights in the room are turned off, the rocks will glow various colors.

Bats

Currently there are three types of bats that inhabit Crystal Cave:

1) Little Brown Bats

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2) Eastern Pipstrelles

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3) Northern Myotis

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Crystal Cave generally has 250-300 bats that live in the caves each year. They hibernate from November to April. Most of these bats can live 20-25 years. On any given summer night they eat 3000 bugs. More bats would live here if there was less commotion going on due to tours. Every day groups and families come to visit the cave. However, many of the bats currently living here have learned to deal with the presence of talking, cameras, and significant lighting.

Fossils

There were many fossils preserved in the rocks of the cave. Many of these are over a million years old. The three types of preserved fossils present are:

1) Cephalopods

2) Gastropods

3) Crinoids

Stalagmites

Stalagmites are formed when water carrying calcite drips down and lands on the floor of the cave. The calcite solidifies when it hits the ground and small "spikes" are created growing upwards to the ceiling.

Stalactites

Stalactites are formed when calcite from the cave is brought down through the cave from flowing water. The cave is very porous and allows a lot of water to flow down from the ceiling. When the calcite hits the air it solidifies and forms the very distinct soda straw features seen in the photograph below.

Columns

Columns are formed when stalactites and stalagmites meet after growing towards each other. This process can take thousands years. These are very distinct features that look like pillars connecting the ceiling of the cave to the floor.

Summary

The cave was a very interesting place to visit. For many of us, it was the first time being in complete darkness, roughly 6 stories below the surface, as the lights were turned off. The cave felt moist in most places as well. It would have been very easy to get lost. Even Blaze told us stories of almost getting lost when he was exploring a new passage. Overall the trip to the cave was a unique experience that we can see locally. Many of us had never been in a cave of that magnitude before. It was great to learn first hand exactly how karst formations came to be. In addition, many of us have never been that up close and personal with bats before. It was an excellent trip and this time the speaker was enjoyable to listen to.