The type of
research that has been done and will be done in Fillmore County
is extensive. Some of the projects include using dye tracing to
establish underground water flows and sampling underground water
to determine its purity, which includes identifying any outside
properties, such as chemicals.
includes speloethem (formations) dating to determine when they
began growing, analyzing speleothems to determine climatic history
and to provide a picture of historic plant life in Fillmore County.
also be work done in bat research and soil sampling to date chronological
development of what is now referred to as Fillmore County. Work
will also be done in soil sampling to search for drugs that will
cure cancer and other human illness.
and radon studies have been done and scientists from around the
United States have used an array of machines on the property to
determine if they are capable of detecting underground voids,
or in other words, caves and caverns.
“Although I enjoy assisting the scientists, my real thrill
is discovering unknown cave systems. In fact, most of the scientists
and researchers encourage me to make such discoveries so they
can advance their research.”
scientists are thrilled with Ackerman's willingness to open the
discoveries of the Cave Preserve to them is because uncommercialized
caves allow researchers an environment free of contaminates. This
is important because interaction with the outside is limited and
formations are relatively unaltered.
The need for
this “natural lab” environment is crucial to the research
Dasgupta is undertaking on speleothems. Commonly called cave deposits,
they are formed when rainwater, which mixes with carbon dioxide
in the soil, becomes acidic, dissolving the limestone when passing
through it. Rainwater then carries the dissolved limestone with
it into the cave below. In the cave the water is no longer able
to carry the limestone in a dissolved state, hence it is deposited,
forming underground structures.
many types of speleothems, but for her work Dasgupta is interested
in stalagmites, the long cylindrical column-like forms that grow
up from the cave floor.
resolution studies of Spring Valley stalagmite records and comparison
with other global records can give us information about past atmospheric
circulation patterns,” she explained.
form by deposition of calcium carbonate on the cave floor from
cave drip waters. When these deposits form in the cave they incorporate
information not only about the ambient temperature of the cave
but also the type of vegetation growing above the cave. Furthermore,
these stalagmites can be dated very precisely by radioactive dating
methods involving uranium and thorium.
speleothem from the Spring Valley Caverns was recently dated to
more than 100,000 years before present, Dasgupta is working with
three stalagmites of different ages.
stalagmite in her present studies ranges in age from 8,500 years
to the present. All the stalagmites were dated in the radioactive
dating laboratory in the Department of Geology & Geophysics
at the University of Minnesota.
radioactive dating technique, Dasgupta also employed band counting
method to obtain ages of the stalagmites. The latter method is
only employed if annual banding is present in a stalagmite, and
in all her samples these bands are present. These bands are fluorescent
bands, which are imaged with a microscope. The combined application
of these two dating methods gave researchers precise ages of the
before, cave deposits can store climatic information in them.
There are chemical species called isotopes, which can vary in
ratio due to a change in the depositional conditions. Dasgupta
has been working with oxygen and carbon isotopes. These isotopes
were analyzed at the stable isotope laboratory in the Department
of Geology & Geophysics at the University of Minnesota.
the ratio of carbon isotopes reflect changes in vegetation above
the cave, and changes in oxygen isotopic composition in the Spring
Valley Caverns mean changes in temperature.
It was found
that both the oxygen and carbon isotopes have varied significantly
in the past. The oxygen isotopes reflect that the area around
Spring Valley was warmest from 6,000 to 5,000 years ago. The temperatures
have started declining from about 2,400 years back, which means
the area is experiencing a colder period compared to 8,000 years
record matches with the oxygen record and shows scientists that
plants conducive to drier conditions dominated during warmer periods.
Recording this information seems to prove that since cool season
plants are more common now, a definite temperature change has
Work is still
in progress regarding analyzes on cave flooding in the area and
this will be able to tell scientists about extreme rainfall events
in Spring Valley.
past climate can help us understand the climate system better
and help in the prediction of future climate changes," said
She is grateful
to have the opportunity to do research in Fillmore County and
encourages others to venture into these caverns.
interested parties to contact him through his Web site: www.karstpreserve.com
has no interest to commercialize his discoveries, Ackerman is
driven by a desire to discover, protect and to perpetually preserve
the caverns for future generations.
“I consider myself a temporary steward of the caves and
as such feel that no single person can 'own' such phenomenal underground
his “legal ownership” of the Spring Valley Caverns,
many are given an opportunity to explore a world beneath the surface
that would not exist without his dedicated work.
Speleological Survey, the University of Minnesota, and the Quarry
Hill Nature Center in Rochester have regular access to the caves.
Boy Scouts and Girl Scouts and many college and high school outing
groups also visit the caves.
very busy. He is married and has three children. He is the owner
of Ackerman's Furniture Service in the Twin Cities. This business,
restoring furniture, employs 15 highly skilled individuals and
is known as one of the top furniture restoration facilities in
the United States.
His main hobby
involves his lifelong love of caves and he is excited to have
found cave number 30 just recently, which is located high up along
the Deer Creek bluff face on his 500-acre Spring Valley Cave Preserve.
point to ponder is that when Ackerman purchased his first parcel
of land, there was only one large cave on it, which had been sealed
for more than 30 years. Even then he had no interest in commercializing
day that I removed the rusty gate from the cave opening is the
day that I allowed scientific researchers in. I consider myself
a spoke in a wheel. In other words, a participant in a circle
which includes conservationists, researchers and scientists, all
of whom are interested in studying and preserving our subsurface
environment,” he said.
one among many who appreciate Ackerman's dedication and willingness
to allow research to the extent he has.
forming deep underground in limestone caves have great potential
to reveal past climate changes. Comparison of this temperature
record with past climatic records from other regions, such as
the North Atlantic region, shows how the climate of southern Minnesota
was linked to the global climate system. And this aspect is important
for studies that model future climate changes,” concluded
On a personal
note, when Dasgupta is not doing research, she works for a voluntary
organization called Vibha, which is dedicated toward helping underprivileged
children in India and the United States. To contact Sushmita Dasgupta,
e-mail her at firstname.lastname@example.org.
Article by Mary Whalen
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