Centralia Mine Fire Analysis:
Presence of Sulfur-bearing Mineral
Deposits at Thermal Vents
Matt Livingood
Jason Winicaties
Jared Stein |
ESL 201 – Fundamental Techniques in Geology
Dr. C. Gil Wiswall
December 15, 1999 |
|
|
Centralia Coal Fire Analysis: Presence of
Sulfur-bearing Mineral Deposits
Abstract
Since 1962, a coalmine fire has spread underneath the surface
of Centralia, located in the anthracite coal region in Columbia County, Pa. In
Centralia, many measures have been taken to cope with the various problems
resulting from the fire. Ultimately, almost the whole town has had to relocate
to other areas due to fear of subsidence, water contamination, and air pollution
from the noxious gases released through vents and fumeroles. Solid, multicolored
deposits can be found on the surface surrounding these vents. The deposits are
believed to be primarily sulfur-bearing minerals deposited hydrothermally on the
surface by the escaping vapors. In this experiment, we collect five different
deposits located around three different vents and one deposit located on an
anthracite sample nearby a vent. We evaluate the six samples for mineral
content, via X-ray diffraction analysis. The results indicate that all
conclusive (3) vent deposits are sulfur-bearing minerals and one particular
sample, on the anthracite, is native sulfur. The native sulfur, found on an
anthracite sample rather then the surface surrounding a vent, is deposited from
bacteria called Desulfovibrio desulfuricans. The bacteria use the carbon
in the coal for energy and reduce anhydrite (CaSO4) and gypsum (CaSO4·H2O)
to hydrogen sulfide (H2S) (Cooney and others, 1999). The hydrogen
sulfide is then oxidized upon contact with the atmosphere, leaving native sulfur
(S0) behind. Other minerals found include Tschermigite and Apjohnite.
Apjohnite was recovered as a coating on a rock removed from the inside of a
vent. Apjohnite usually is white to pale yellow, has a hardness of 1.5 to 2, and
has encrustation (forms crust-like aggregate on matrices) habit (Barthelmy,
1999). Tschermigite, also known as ammonia alum, is soft (hardness = 1.5-2.0)
and is usually white to colorless (Barthelmy, 1999). Tschermigite is very rare
and only found natively in Czechoslovakia, but also has been reported to form as
deposits around volcanic vents and fumaroles (Lowenstern, 1999). For the
tschermigite and apjohnite, the sulfur compounds release from the coal and
dissolve into the heated fluid, where they react with other dissolved ions
present in solution. They are then carried to and deposited on the surface by
these hydrothermal fluids. At the surface, the liquids cool and the sulfur
minerals are precipitated from the solution. The presence of Tschermigite
suggests that the coal mine fires of Centralia are quite similar to other high
temperature regions on earth, particularly volcanically active areas.
Introduction
Throughout much of Centralia there are cracks and holes in
the ground with a harsh steam constantly pouring out. The trees are all dead and
white in color and the ground is so hot your feet sweat. There is a sulfur smell
to the steam and two hours of exposure was enough to give my colleagues and I
headaches. Around these surface holes, or vents, different colored deposits are
scattered in a wide range of sizes. These deposits are very interesting for they
exhibit various colors and forms. It is the goal of our research to collect
these deposits for observation and X-ray diffraction analysis. We infer that
these samples are sulfuric in nature from the smell of the vapor rising from the
vents. From the analysis, we hope to conclude that these deposits are primarily
sulfur and/or sulfur-bearing minerals. Also, we hope to gather enough evidence
to formulate a theory on how the deposits were extracted, transported, and
deposited.
We chose to research the Centralia mine fire because of the
great tragedy it presents. The residents of Centralia have had their lives
shattered by the fires from stress of relocation and/or medical complications.
Also, we chose Centralia because the area resembles a post-nuclear war wasteland
and is very unique. The sulfury smell, rocky smoking hillsides, absence of
people, and ghostly white smoldering trees present an eerie landscape sparking
the interest of my colleagues and I. Specifically, we chose to concentrate our
experiment on the vent deposits. The deposits are unlike any other surface rocks
or features we observed in Centralia and we were very curious of there nature.
From the experiment, we hoped to gain an understanding of the origin, methods of
transportation and deposition, and classification of these deposits. We also
wish to further our knowledge of the landscape characteristics and history of
the Centralia mine fire.
Centralia Fire History
Centralia is located in the anthracite coal region of Eastern
Pennsylvania, in Columbia County. In the summer of 1962, a fire started in the
Buck Mountain coal bed. At this time, there were about 1,100 residents with 545
families and businesses in Centralia (PDEP, 1996). The mine fire is believed to
have started from an accidental fire at the landfill located at the southern end
of the town. >From here, the fire spread igniting an open coalmine shaft and
spreading throughout the abandoned mines. By 1983, the fire consumed
approximately 195 acres of area (Logue and others, 1991), and the main road into
town, Route 61, suffered severe subsidence damage (PDEP, 1996). In 1983, the
Office of Surface Mining (OSM) was authorized by the Department of Health to
reclaim public lands and private establishments deemed hazardous, and over 30
houses were moved away. The OSM released a report in 1983 estimating that the
fire could spread to 3,700 acres and "burn for a century or more if left
uncontrolled" (Logue and others, 1991). Hazards included subsidence, noxious
gases, oxygen depletion, and particulate matter. "A study estimated it would
cost $663 million to extinguish what some call "the granddaddy" of all mine
fires", says Lynne Glover in the Tribune review. Because the estimated cost of
relocation was only about 42 million, relocation was chosen as the answer to the
fire. The coal bed will eventually burn out when the coal seem ends, so the
neighboring towns are believed to be safe (Glover, 1998). In 1984, Congress set
aside $42 million dollars and begins to relocate families and businesses. The
Milton S. Hershey Medical Center released a report that concluded Centralians
had higher incidences of respiratory disease, hypertension, gastrointestinal
disease, arthritis, and depression in Feb. 1986 (Logue and others, 1991). In
1993, Route 61 is closed indefinitely after several attempts to repair it. The
53 remaining households are condemned but the remaining residents still refuse
to leave. By 1996, there were <46 remaining residents (< 5% of the original) of
Centralia (20 families) and the total costs of relocation exceed $35 million
(PDEP, 1996).
Anthracite Characteristics and Geology
The anthracite coal beds of eastern Pennsylvania cover an
area of about 1250 sq. km and constitute over 97% of the total U.S. anthracite
resources (Funk and Wagnall’s, 1999). There is approximately 15 billion tons of
recoverable coal in this region, enough to supply anthracite for the next 400
years (Centralia Coal, 1999). The anthracite coal beds were deposited in the
Pennsylvanian, ~300 ma. During this period of the Carboniferous, the region was
predominantly lowlands and forested swamps periodically covered by shallow seas.
Trees and ferns constitute the majority of the Pennsylvanian plant life. For
coal to form, the plant matter must be deposited underwater to avoid oxidation
to water and carbon dioxide. The plant matter was then transformed by
biochemical and physical processes (metamorphic events from subsequent
orogenies) into a dense consolidated carbon-rich rock (Levin, 1996). Different
coals are produced in a succession depending on time and metamorphic stress
starting with peat, to lignite, bituminous, and finally anthracite (Bell and
Wright, 1985). Anthracite coal has the highest fixed carbon, 93-98%, and lowest
volatile material of all coals. Anthracite is a hard, glossy black rock with
concoidal fracture. Although harder to ignite, anthracite (ignition at about 225°
C) releases large amounts of energy (7000 - 8000 cal./ kg) when burned with less
smoke and soot as bituminous (ignition at about 150°
C) and lignite coals (Funk and Wagnall’s, 1999; Glover, 1998; Mottana and
others, 1978).
Other Underground Coal Fires
There are other places in Pennsylvania and around the world
where underground coal fires burn. Pennsylvania has over 250,000 acres of
abandoned mine lands and has >1/3 of the nations mine problems. There are over
45 mine fires burning across Pennsylvania. There are five underground fires in
Allegheny County, five in Percy County, one in Westmoreland, and others in more
isolated areas. There are also fires in Findlay Twp., West Elizabeth, Plum, and
Clinton. "In all, the DEP estimates about 1,300 acres across the state are on
fire underground" (Glover, 1998). One particular town, Youngstown, is under the
wrath of the Percy fire that has been burning for over 30 years. There are about
60 homes resting on top of this fire now. Youngstown is reaching the critical
decision point that Centralia reached in 1983, either extinguish the fire or
relocate the whole town. Estimates conclude that extinguishing the Percy fire
will cost $30 to $40 million, and over $650 million to put out all nationwide
fires (Glover, 1998).
A very large underground fire burns through large coal beds
in Northern China. The fires consume up to 200 million tons of coal each year.
This fire is quite a bit larger then the largest Pennsylvania fire (Centralia),
releasing almost "as much carbon dioxide into the atmosphere as do all the cars
in the United States" (Kittl, 1999). The Chinese haven’t really paid much
attention to the fire until recently. Now they monitor the fire with heat
sensitive satellite photographs. Areas of subsidence have caused very large
cracks in the surface and there are areas where one can observe the burning beds
above them on the side of a cliff. The Chinese are now taking measures such as
burying the coal with dirt and pouring a water-clay mix into surface cracks to
cool the fire. They feel the only way to deal with these fires is to try to
isolate them and let them burn out (Kittl, 1999).
Mineralization of Sulfur
Sulfur (S) is distributed in the crust in mineral forms
such as iron pyrites, sphalerite, galena, gypsum, barite, and others. It also
"occurs native in the vicinity of volcanoes and hot springs" (Hammond, 1975).
Sulfur is yellow, has a low specific gravity (2.0), and is brittle (Cepeda,
1994). The sulfur in the deposits comes from mineral and organic sulfur in the
anthracite. The sulfur in Anthracite can be divided into three categories:
pyritic sulfur, sulfate sulfur, and organic sulfur (Alvarez and others, 1997).
Pyritic sulfurs, also called sulfide sulfurs, constitute anywhere between 25-75%
of the total sulfur and are contained in minerals such as pyrite and marcasite
(FeS2) and sphalerite (ZnS) (Chinchon and others, 1991). During
combustion, sulfide sulfurs release in the form of their oxides at about 500°
C.
2 FeS2 + 5 O2 ®
4SO2
+ 2FeO
The organic sulfurs, 20-70% total sulfur, are sulfurs
incorporated into the organic molecules of the plant material and also release
around 500° C. Sulfate sulfurs usually are in the
form of gypsum (CaSO4) and decompose to CaO and CO2 at 500°
C. The sulfates don’t release as sulfur dioxide until 1060°
C, a temperature where 13.70% of the initial sulfur still remains. Thus a large
percent of the sulfur still remains in the form of anhydrites (Alvarez and
others, 1997; Chinchon and others, 1991).
Sulfur oxides, primarily sulfur dioxide (SO2), are
released in gaseous form into the atmosphere. For underground fires, the sulfur
byproducts are, in part, dissolved into the heated surface groundwater and
transported to the surface. Other byproducts are released in gaseous form.
Sulfur has a low melting point (175° F) and is easily
dissolved. The sulfur oxides react with other ions in the fluids and/or the
atmosphere and precipitate out sulfur-bearing minerals during condensation at
the cooler surface.
Native Sulfur can form if the proper conditions are met, low
temperatures and the presence of an energy source. At these conditions, bacteria
called Desulfovibrio desulfuricans use the carbon in the coal as the
energy source (Cooney and others, 1999) in a reaction that reduces the sulfur
from anhydrites (CaSO4) and gypsum (CaSO4·H2O)
minerals in the coal. The sulfur is then released in the form of hydrogen
sulfide (H2S), which is then oxidized in the atmosphere to form
native sulfur (Cepeda, 1994).
Data and Observations
Deposit samples were collected from 3 different sites.
Site 1 and site 2 are separated by approximately 100 feet and are located in a
ravine on the west side of Route 61 at the subsidence damage site. Site 3 is
located to the Northwest of sites 1 & 2 at the landfill where the coal beds
initially caught fire.
Site 1: Site 1 was a
small area at the bottom of the ravine. From Site 1, we collected one sample
labeled "white crystal". White crystal deposits were scattered lightly over
about a 25 sq. ft area. The "white crystal" was concentrated in roughly a 6 x 3
inch area that was located next to a fissure to the downhill. The fissure was an
8 to 10 inch crack in the surface with water seeping out and moist soil
surrounding it.
Site 2: Site 2 was the surroundings of a
larger fissure on the eastern side of the ravine. It was located about halfway
up the hillside and steam/smoke was escaping from the hole and surrounding
cracks. From this site, we collected four samples labeled: "yellow chunk",
"white chunk", red chunk", and "green crystal". The red, yellow, and white chunk
deposits were massive in nature, brittle, and homogenously deposited around the
vent. The three different colors exhibited no visual zoning and apperared to be
similar. Large masses, up to ~4 inches in diameter, displayed color changes
within crystal itself. Some samples displayed all three colors within
themselves.
The "green crystal" deposits were found on a relatively
rectangular sample of anthracite roughly 24in. x 10in. x 3in. in size located
downhill from the vent. The anthracite was charring on the underside and the
crystal deposits were located on the side of the rock at the junction of the
side and top faces. The anthracite sample was located about 5 feet downhill from
any visual vent activity and did not appear to be associated with the vent
itself at this particular time.
Site 3: Site 3 was located a couple
hundred feet northwest of the first two sites, at the landfill. This area was
the landfill where the fire initially ignited the coal seam. There are many
fissures scattered around the area and the ground is exceptionally warm here.
Site 3 is a large hole in the bedrock with steam pumping out and a white film
covering all the associated rocks. The deposit is scraped from a rock taken from
inside the vent. The sample appears to be a white, porous film baked onto the
rock.
The samples were collected in plastic zip-lock bags and
labeled accordingly. The samples were then crushed into a fine powder using a
mortar and pestle. The powder was analyzed by X-ray diffraction and peaks were
correlated on a sulfate database to search for sulfur-bearing minerals. Results
are printed and placed in a data table.
The data table is provided in figure 1:
Figure 1
Site # |
Sample name |
Color |
Characteristics |
Major mineral or component |
Chemical Composition |
|
|
|
|
|
|
1 |
white crystal |
bright white |
fine, powdery crystals |
Inconclusive |
---------- |
|
|
|
|
|
|
2 |
red chunk |
rusty |
massive |
Inconclusive |
---------- |
|
|
|
|
|
|
|
white chunk |
white |
massive |
Tschermigite |
(NH4)Al(SO4)2·12(H2O) |
|
|
|
|
|
|
|
yellow chunk |
pale yellow |
massive |
Tschermigite |
(NH4)Al(SO4)2·12(H2O) |
|
|
|
|
|
|
|
green crystal |
green yellow |
fine crystals |
Native Sulfur |
S |
|
|
|
|
|
|
3 |
white porous |
white |
white, bubbly film |
Apjohnite |
MnAl2(SO4)4
× 22H2O |
Results and Conclusions
The "green crystal deposits found on the anthracite
sample are native sulfur. The conditions were suitable for Desulfovibrio
desulfuricans to flourish. Desulfovibrio desulfuricans use carbon for energy so
the carbon-rich anthracite offers a substantial source of energy. Also, the
anthracite sample was on the surface so the temperatures were low enough for
Desulfovibrio desulfuricans to grow. The bacteria use the carbon in the coal for
energy and reduce anhydrite (CaSO4) and gypsum (CaSO4·H2O)
to hydrogen sulfide (H2S) (Cooney and others, 1999). The native
sulfur was deposited from oxidizing hydrogen sulfide released by the bacteria.
The massive yellow and white chunk samples from site 2 are
Tschermigite, in the sulfosalts category (Cepeda, 1994). The deposits are
located on or adjacent to the fissure and are bulky rather then widely
scattered. Since tschermigite is found only in Czechoslovakia, it is not
initially part of the Centralia rock sequence. Tschermigite minerals have been
noted around the world near volcanically active regions and other "hot spots".
The presence of Tschermigite in bulky samples leads us to conclude that the
samples are hydrothermally deposited from heated waters rising to the surface.
"Sulfosalts occur primarily in hydrothermal ore deposits-deposits formed by the
crystallization of elements concentrated and carried in a hot water solution
produced as magma cooled or by water flowing through a hot fractured rock"
(Cepeda, 1994). The coal fires burn very hot and heat groundwater to
temperatures well above 100º C. The sulfur compounds dissolve into the solution
and react with other ions present in the solution to form the deposit molecules.
The deposits precipitate out of solution upon contact with the cool air at the
surface. The presence of Tschermigite suggests that the coalmine fires of
Centralia impose characteristics to the surface quite similar to other high
temperature regions on earth, particularly volcanically active areas and "hot
spots".
The apjohnite samples obtained from inside the vent at site 3
are also hydrothermally deposited. Apjohnite is usually white and found as a
coating, which is characteristic of the samples we obtained. Because the
apjohnite is coated over existing rocks rather then blocky monolithic forms, it
is concluded that the apjohnite is deposited on the surface through the steam
rather then rising waters as with tschermigite. As the hydrothermal solution
reaches the surface, the apjohnite precipitates out of the gases and then
deposited. This causes the sprayed, or coated effect. Apjohnite has a very
similar chemical make-up as the tschermigite, suggesting that only slight
differences exist between the two vents. The chemical compositions of the two
minerals are shown in figure 2.
Figure 2
|
Tschermigite |
Apjohnite |
Chemical |
|
|
Oxygen |
70.59% |
68.35% |
Aluminum |
5.95% |
6.07% |
Hydrogen |
6.23% |
4.99% |
Sulfur |
14.15% |
14.42% |
|
N = 3.09 % |
Mn = 6.18 % |
The similar chemical components’ weight %’s of the two
minerals are correlated to quantitatively evaluate the similarity. The
correlation coefficient is an extremely high 0.999692, suggesting very
strong correlation and close similarity. The correlation plot is shown as figure
3.
Figure 3
The difference between the tschermigite and apjohnite is the
presence of nitrogen in tschermigite and manganese in the apjohnite. The two
vents are a few hundred feet apart and may be running through slightly different
bedrock altering possible ions that enter the solution. Also, the temperature of
the ground at site 3 was much higher then at site 2. Different temperature
waters have different solvent properties so what may dissolve in one
hydrothermal solution may not dissolve in another. This may also explain the
different modes of deposition for the two sites. If the groundwater at site 3 is
much hotter then at site 2, the steam will escape faster and may distribute the
precipitates in more of a spray fashion.
The "white crystal" from site 1 and the "red chunk" from site
2 are also believed to be hydrothermally deposited based on their depositional
distribution and appearance. Both samples are located next to vents and are
resting on moist ground. Unfortunately, strong conclusions could not be made
because the X-ray diffraction analysis yielded no strong matches for these two
samples. When the "red chunk" sample was tested, "chromium sulfate hydra"
resulted with a pretty good match. We hypothesized that the red chunk samples
would be similar to the tschermigite samples based on the relative locations of
these samples and visual similarities. Neither tschermigite nor apjohnite show
up in X-ray analysis of the red chunk samples. Further investigation of the red
chunk samples is necessary to determine what the nature of this deposit is. A
change may have occurred in the origin, transport, or deposition of these
minerals. We have a few hypotheses: the deposits are from a different vent or
are remains from a different time, the deposit has encountered a chromium rich
chemical which has reacted with the mineral, the deposits molecules originate
from a relatively small, chromium-rich inconsistency in the coal. Re-sampling,
closer visual observations, and re-analysis of old and new samples are
recommended to solve this problem. Analysis under different measurement such as
chemical composition may reveal an answer as well, but not possible due to time
restrictions. It is recommended in additional studies to run the X-ray
diffraction analysis for these two samples for a longer duration, possibly an
hour or two. Longer runs may yield better data for the "white crystal" and "red
chunk" samples.
Discussion
Centralia, a small town located in Columbia County,
Pennsylvania, has been plagued by an underground mine fire in the Buck Mountain
anthracite coal beds since 1962. In less then 40 years, 95% of the population
has been relocated to neighboring areas by the government to an effort to avoid
potential hazards such as noxious gases and subsidence.
Vents and fissures are scattered all throughout Centralia
relieving the increased underground pressure caused by the fires. Sulfuric steam
and smoke rise from these vents and different colored deposits surround the
fissures. The deposits are collected and, via X-ray diffraction analysis, found
to be either native sulfur or sulfur-bearing minerals, proving the hypothesis.
The native sulfur is deposited on an anthracite sample from which the bacteria,
Desulfovibrio desulfuricans, utilize carbon for energy to reduce the anhydrite
and gypsum to hydrogen sulfide. The atmosphere oxidizes the hydrogen sulfide and
native sulfur is formed. Apjohnite samples are found as a crust formed on the
rocks through which a vent travels at site 3. The apjohnite crust coats the
entire vent structure and is white with a slightly vesicular appearance.
Apjohnite is deposited through precipitation from condensing steam that
distributes the mineral as a coating over the vent. At site 2, tschermigite
deposits are found as blocky masses right at the vent openings suggesting
hydrothermal deposition from heated groundwater. Apjohnite and tschermigite
samples have similar compositions with the chemical components wt. %’s
correlating to 0.999692. This suggests that these samples are derived similar
with possible slight differences in bedrock and/or solvent temperature.
Tschermigite is usually only found around volcanically active areas displaying
the similarity between Centralia and other "hot spot" areas. Centralia is not
the largest coal fire in the world, yet the emotional and psychological stresses
it has caused are unparalleled by any other underground fire. The Centralia mine
fire could conceivably burn for another century. Unfortunately, the damage has
already been done.
References Cited
- Alvarez, R., Clemente, C., and Gomez-Limon, D., Nov. 1997, Reduction of
Thermal Coals Environmental Impact by Nitric Precombustion Desulfurization,
Environmental Science and Technology, vol. 31, pp 3148-53.
- Barthelmy, D., May 1999, Mineralogy Database – Apjohnite Mineral Data,
http://web.net/%/Edaba/Mineral/data/Apjohnite.html
- Barthelmy, D., May 1999, Mineralogy Database – Tschermigite Mineral Data,
http://web.net/~daba/Mineral/data/Tschermigite.html
- Bell, P., and Wright, D., 1985, Rocks and Minerals, Macmillan Publishing
Company, New York, pp 12, 347.
- Centralia Coal Company, 1999, Centralia Coal Company Homepage,
http://www.centraliacoal.com.
- Cepeda, J. C., 1994, Introduction to Rocks and Minerals, Macmillan College
Publishing Company, New York, pp 22, 28.
- Chinchon, J. S., Querol, X., and Fernandez-Turiel, J. L., Jul/Aug 1994,
Environmental Impact of Mineral Transformations undergone during Coal
Combustion, Environmental Geology and Water Sciences, vol. 18, pp 11-15.
- Cooney, M. J., Roschi, E., Marison, I. W., von Stockar, U., and Comninellis,
C., 1996, Physiological Studies with the Sulfate-Reducing Bacterium
Desulfovibrio Desulfuricans – Evaluation for Use in a Biofuel Cell, Enzyme and
Microbial Technology, vol. 18, iss. 5, pp 358-365.
- Department of Environmental Protection, Feb. 1996, A Brief History of the
Centralia Mine Fire (Borough of Centralia, Columbia County),
http://www.dep.state.pa.us/dep/deputate/minres/BAMR/centbrf.htm
- Funk and Wagnall’s Encyclopedia, 1999, Anthracite,
http://www.funkandwagnalls.com/encyclopedia/low/articles/a/a002000347f.html
- Glover, L., May 1998, Burning Beneath the Surface,
http://www.penweb.org/issues/mining/tribrev/swfires.html.
- Glover, L., May 1998, Mine Fire Still Rages Beneath Tiny Town,
http://www.penweb.org/issues/mining/tribrev/centralia.html.
- Hammond, C. R., 1974-1975, CRC Handbook of Chemistry and Physics, CRC Press,
Cleveland, 55th ed., pp B-31.
- Kittl, B., Oct. 1999, China’s on Fire, Discover Magazine, Walt Disney
Company, New York, vol. 20, no. 10.
- Levin, H. L., 1996, The Earth Through Time fifth edition, Saunders
College Publishing (Harcourt Brace College Publishers), Orlando, pp 324-341.
- Logue, J. N., Stroman, R. M., and Sivarajah, K., Jul/Aug 1991, The Centralia
Mine Fire; An Overview of Community Health Surveillance Efforts, Journal of
Environmental Health, vol. 54, pp 21-23.
- Lowenstern, J., 1999, USGS-Alid Volcanic Center in Eritrea, NW Africa,
http://wrgis.wr.usgs.gov/lowenstern/alid/alidphotos.html
- Mottana, A., Crespi, R., and Liborio, G., 1978, Simon and Schusters Guide to
Rocks and Minerals, Simon and Schuster Publishing Company, New York, pp 12, 347.
|