Transcript Petrifying Well - Northwestern University

Petrification
Jen Cowman
Sakinah Alhabshi
CEE 367
Spring 2003
What is Petrification?
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The replacement of the normal cells of organic
matter with other minerals
According to evolutionary doctrine, petrification
requires much time, usually millions of years,
but how much time is really needed in this
process?
Things are usually petrified in soil or by a water
source with a high mineral content
Affected by – temperature, pressure, minerals
Mother Shipton’s Petrifying Well
Yorkshire, England
Background
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Available for public viewing since 1630 – cascades from
River Nidd & forms an aqueous curtain to Mother
Shipton’s Cave
High mineral content:
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calcium, sodium and magnesium
traces of lead, zinc, iron, manganese and aluminium
Exist mainly as sulphates and carbonates, with some
chlorides and a trace of silica
Proportions have remained more or less regular over
many years
Facts
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As dissolved calcite (CaCO3) is exposed to air,
CO2 escapes and the limestone is deposited
2HCO3- + Ca2+  CO2(g) + CaCO3(s) + H2O
Petrifies sponges/teddy-bears: 4-6 months,
Animals: 12-18 months
Flow of 700 gal/hr
Making a Profit?
Souvenirs undergoing petrification to be sold to
tourists – basket, teddy-bears, sponges, books,
gloves, foxes, cats, dogs, birds, and boots
Effects
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Tufa – soft rock
Travertine – hard rock
Dark/light bands
The face of the rock has
to be scoured every 6
weeks to prevent it from
getting top heavy and
falling over
Petrified Forest National Park
Petrified Wood, Arizona
Requirements
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The dead wood needs to be protected from
decay
The dead wood becomes saturated with mineralladen water
The porous nature of wood allows the
movement of water-borne particles
The water itself needs to harbor specific
minerals necessary for petrification
How?
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After burial and saturation, chemical
reactions take place between the
minerals and the cellulose
compounds in the cell walls
Mineral crystals grow in the spaces
left behind by the dissolution of the
cell walls
Two phases of crystal deposition
result in complete mineral
replacement of the wood
Cross-section, cell walls infiltrated
by quartz. X350
Colors?
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Minerals - iron, manganese,
carbon, and chromium, cause the
colors of the petrified wood
Red – iron
Green – chromium
Black – carbon / magnetite
Yellowstone National Park
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Continental “hot spot” in Wyoming
Mammoth Hot Spring Terraces
100 hot springs scattered over terraces
 Thermal springs deposit CaCO3 as travertine
between 2.8 – 56.5 cm/year
 Silica deposition rates into blocks of wood in
alkaline springs at Yellowstone between 0.1 and 4.0
mm/yr
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Liberty Cap
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Liberty Cap
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45 ft tall
Cone formed from a
steady flow of hot water
from a single source
Presently inactive
Opal Terrace
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Opal Terrace
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160° F
Known for its pastel colors
A tennis court had to be removed because it grew too quickly
New Highland Terrace
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Terracette
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Semicircular ledge formed
by travertine that is
deposited around slowly
rising pools
Hot water flows over the
lip and forms stalactites
“Instant” Petrified Woods
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Advanced Ceramic Labs at the University of Washington,
Seattle
Wood-ceramic composites 20–120% harder than regular
wood
Simple process – soak wood in silicon and aluminium
solution, then oven-cure at 44°C (112°F)
Hamilton Hicks, Connecticut – made a chemical 'cocktail' of
sodium silicate, natural spring or volcanic mineral water high content of calcium, magnesium, manganese and other
metal salts, and citric or malic acid
Potential Uses for
“Instant” Petrified Woods
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Fireproofing wooden structure
Longer-wearing floors and furniture
Greater strength wood
Insect, decay and salt-water proof wood in
buildings
Conclusions
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Misconception: fossilized wood buried in rock
strata must have taken thousands, if not
millions, of years to petrify
Can be rapid
Good knowledge base – we can make petrified
wood for our benefit