Mystery Cave
Introduction: We went to Mystery Cave to see what the environment was like in the cave and
to test the water outside of the cave and inside of the cave. The first thing that we did was
explore the cave and learn about the cave formations and how they were created. We took a
sample of some water inside of the cave to later test the pH, Alkalinity, hardness, nitrite, nitrate
and chlorine and to also compare those results to the water outside of the cave.
Predicted Results:
1. Compare water inside cave to the water before it enters the cave.
 Nitrite would stay the same because it stayed the same in the 9 other water
samples that we tested so we assumed it would stay the same in the cave from the
stream.
 Nitrate stays the same because it stayed the same in the 9 other water samples that
we tested so we assumed it would stay the same in the cave from the stream.
 PH would go up because it comes in contact with the limestone which makes
more neutral.
 Hardness would be higher outside of the cave than inside because there is nothing
inside the cave to soften the water.
 Alkalinity would be higher because of the limestone found inside the cave.
 Chlorine would be 0 because there shouldn’t be any chlorine in either the stream
or the cave and there was no chlorine in any of our water tests.
2. Compare cave water to Aquafina.
 Nitrite-same
 Nitrate-same
 PH-down
 Hardness-up
 Alkalinity-up
 Chlorine-same
3. Compare cave water to rain.
 Nitrite-same
 Nitrate-same
 Ph-up
 Hardness-up
 Alkalinity-up
 Chlorine-same
4. Compare cave water to lake
5.
6.
7.
8.
9.
 Nitrite-same
 Nitrate-same
 Ph-up
 Hardness-up
 Alkalinity-up
 Chlorine-same
Compare cave water to Andy’s softened
 Nitrite-down
 Nitrate-down
 Ph-up
 Hardness-up
 Alkalinity-up
 Chlorine-same
Compare cave water to Andy’s Tap
 Nitrite-down
 Nitrate-down
 Ph-up
 Hardness-up
 Alkalinity-up
 Chlorine-same
Compare cave water to Johns Tap
 Nitrite-down
 Nitrate-down
 Ph-up
 Hardness-up
 Alkalinity-up
 Chlorine-same
Compare cave water to John’s R.O.
 Nitrite-up
 Nitrate-up
 Ph-up
 Hardness-up
 Alkalinity- down
 Chlorine-same
Compare cave water to city
 Nitrite-down
 Nitrate-down
 Ph-up
 Hardness-up


Alkalinity-up
Chlorine-same
Overall our group decided that the water in the streams would be less acidic before
entering the cave. We predicted this because it hadn’t passed over the rocks in the cave yet to
gain acidity. Due to our tests in class, we felt somewhat certain of our predictions. On the table
below there are the results of our class’s tests on the two sources of water. We also predicted that
there would be a change in alkalinity; we said that it would go up. This again is because the
water would have to travel over the rocks and thus would then become higher in alkalinity.
TESTS
PH
ALKALINITY
HARDNESS
NITRATE
NITRATE
CAVE
8.4, 8.4, 8.4, 7.8
240, 240, 240, 240
425, 425, 425, 425
0, 0, 0, 0
5, 5, 5, 0
STREAM
7.2, 8.4, 7.8
240, 240, 240
250, 250, 425
0, .15, .5
5, 2, 2
As can be seen here our predictions were somewhat off. After we tested the water we
were able to see that the PH went up making the acidity less and the alkalinity stay the same.
Nitrate and Nitrate seemed to fluctuate but not enough to really make a huge difference.
Procedure: We took a bus to Mystery Cave which is located in Forestville State Park. As soon
as we got there we were introduced to our tour guide Kate. We then walked across a
bridge and entered one of the entrances to the cave. While in the cave she talked about
different activities that could be done in the classroom before taking the students to the
cave. She made it clear that if you prepare the students with information about the cave
before they come then it will be more interesting to them and they will get more out of it
when exploring the cave. We as college students also prepared for this field trip. We
took different water samples that included, Aquafina, rain, river, lake, Andy’s softened,
Andy’s tap, John’s tap, Andy’s RO and the city water. We tested them for Nitrite,
Nitrate, pH, hardness, alkalinity and chlorine. We did this water test to compare and
predict the water to inside and outside of the cave. A second experiment that we did was
called “Acid and Rocks.” In this experiment we mixed acid with Limestone and Granite
to observe the changes and reactions. This helped us make predictions for the cave water
because we learned that acid has an effect on Limestone. As she explained the different
cave formations and how the cave was formed, we found it helpful to take notes and
pictures to help with this report. We collected water from the inside of the cave and
water from the stream outside of the cave to see if what we predicted was accurate.
Results: (These are our results from the cave water and stream water outside the cave)
Type of
Water
pH
Alkalinity
Hardness
Nitrite
Nitrate
Cave Water
8.4, 7.8
240
425
0
0,5
Stream
Water
7.2, 7.8, 8.4
240
250,425
0,.5,.15
2,5
Cave Coral
Sinkhole
Fossil
Raft Cone
Stalactite
Discussion of Results: We learned that there used to be an ocean where Mystery Cave is now.
Shell animals died and fell to the bottom of the ocean. As the water goes through the
crevasses it eventually breaks down the Limestone creating caves. As we were walking
through the cave we noticed fossils of the different shelled animals. Our tour guide
compared these fossils to squid.
The cave guide told us that there are four species of bats that live in the cave and
that the bats were hibernating at this point in time. Bats and Spring Tails are the only
living creatures in the cave because no sunlight is present in the cave. If other animals
lived here they would not survive because of the lack of nutrients that they would get
from the sun. The Spring Tails are white bugs that sit on top of the water. They feed off
of human’s dead skin cells. After she told us about the animal life we walked further into
the cave and saw different formations.
One of the first things that we saw was Flowstone. Flowstone was formed
because of the water that dripped down from the walls of the cave and then stopped
flowing. It is also a layer of Calcite.
The next thing we saw were straws. Straws are hollow and thin which are formed
by droplets of water that do not fall on the floor making them form downward from the
ceiling. A straw will eventually turn into stalactites. The straw gets thicker and bigger
and eventually looks like an icicle. We were then introduced to Stalagmites. Stalagmites
are formed when water drips from the ceiling of the cave creating mounds of calcite on
the ground that build up over time. Sometimes stalagmites are crooked. This is because
the stalactite is formed first and then the iron expands causing this effect. Straws,
stalagmites and stalactites all contain Calcite.
We then saw something that looked like cauliflower or popcorn. We were told
that it is called “Cave Coral.” Cave coral has a rough texture and spread over large areas.
This is just another form of the layers of Calcite on the cave wall.
In the second cave, we walked past a pool of water that was about a foot deep.
The pool was formed by dripping water and as we looked at it, we noticed that there were
tiny white specks everywhere and huge cone like structures were coming up from the
water. Kate told us that over time the little specks of calcium build up and form raft
cones.
After the first part of the cave tour, we went and looked at a sinkhole that was
located in the middle of the woods. A sinkhole is caused by the removal of soil and
plants on the ground by water. We also went and looked at another sinkhole called
Goliath. Goliath could have been formed from part of a cave collapsing or the lowering
of the water table. We did an experiment dealing with wells and how they become
polluted.
Our group was given an “aquifer bottle” that consisted of two sandy aquifers
separated by a clay aquiclude. The lower aquifer represented a confined aquifer, and the
upper aquifer is unconfined. Porosity is the spaces between the sand particles and
permeability is the ability for water to move through rocks. After we put water through
our well and made sure that it worked properly we concluded that the lower well owner
gets more water and the water is more filtered because it has to go through all of the
layers and it also gets flushed out faster. The upper well owner would eventually end up
going dry because of the water table. We then added a “pollutant” to our well. From
this, the upper well owner would be pretty upset because they saw the pollution a lot
faster than the lower well owner. We needed to remove the pollution from the well and
not put it back into the water table. We would have had to bury it somewhere outside of
the water table that way it would not pollute the water again. We had to flush out the
well with water until it was clean again. It would also be a good idea to cap the pollution
somehow to keep it from spreading even more. This experiment showed us how water
gets contaminated like it does when people pollute the sinkholes.
The water hardness in the cave was higher than the stream water because there is
calcium in the cave. The Alkalinity was the same for both the cave and stream water
because alkalinity neutralizes the acid in the water and it does not change the level of the
pH. Rain water is acidic and when it goes into the cave, the limestone dissolves and the
water becomes more neutral because the limestone neutralizes the acid. This is why the
water in the cave is neutral. If there was a lot of nitrate in the water we would know that
the water has been contaminated. According to our results, the nitrate level was basically
the same for the cave and stream water. The nitrate that is there could be caused by
pollution or fertilizer. There may be some Nitrite in the stream because it is produced by
fish and decomposing matter. The nitrite would not be in the cave because the water is
filtered through the soil and rocks.
One thing that our group noticed was that the pH was about the same in both the
cave and the stream. This is different from what we predicted because we thought that the
water in the stream had to be acidic in order to break down the limestone. We thought
that maybe the rainwater just got in through the sinkholes and eventually moved through
the cracks and crevasses and eventually broke down the limestone. We also thought that
maybe when the water moved through the soil it picked up particles such as decomposing
matter and became acidic. The water would become neutral again once it came in contact
with the limestone.
Conclusion: In conclusion, after we tested the water that we collected in the cave
and outside the cave in the stream we decided that we would probably get the same
results in any other tests that we might conduct with this idea. Although, we did have to
include the factor of the caves “beginning” so to speak when considering other tests. The
cave that we toured was formed by an ocean and was primarily of limestone. Limestone
is formed by the animals that die in the ocean and their shells and outer layers being
pushed down to the ocean floor and building up for quite some time. Since the elements
that surround the cave have a major affect on how the cave is formed, our predictions
may vary slightly if we tested another cave that wasn’t formed by the same element. i.e.
an ocean. When testing the water in the different caves, one must take in to consideration
where that water has traveled. Did it drip in from somewhere, is there a constant flow of
water somewhere, what rocks did it have to go over or drip through to get to the testing
site and so on.