Pele`s hair and tears-their origin and composition

Pele`s hair and tears-their origin and composition
Diana Oettel (48943), TU Bergakademie Freiberg
Fig.1. Pele-the goddess of fire and volcanoes (WEB 1)
Abstract. Lava Fountains are one of the most impressive volcanic phenomena. In
these fountains lava is ejected to great heights under high speeds and temperatures, producing pyroclastic products such as lapilli, spatter, pumice and scoria.
This paper presents a collection of chemical and physical studies on Pele´s hair
and tears, showing their association according to their formation. Chemical zonation rims on both of them allow to assume an interaction of these glasses with acid
gases in the plume. Furthermore vesicle studies display volatile exsolutions before
and after the eruption.
2
Diana Oettel
Introduction
Many native Hawaiians have a strong
belief concerning Pele, the goddess of
fire and volcanoes. In the hawaiian
legends, she is described as a handsome, young woman, who settled in
Hawaii after she was banished from
her home because of a conflict with
her sister, the goddess of the sea. Pele
traveled from the most northwestern
islands to Hawaii, digging craters on
every island. Every time her sister
Fig.2. Pele`s hair (WEB 2)
chased her to the next island. After a
huge fight on Maui Pele went to the Halemaumau crater and has been living there
since. Sometimes people believe seeing her and her white dog running across
lava fields near Kilauea (Big Island). This myth indicates that the Hawaiians
were keen observers of their environment. First they understood that the volcanism becames younger in direction to Big Island. That is because the island chain
is passing over a hot spot in the earth's mantle. Second you can find pyroclastic
products after eruptions of many basaltic volcanoes. Among Pele´s hair (Figure 2) and tears (Figure 3) you can find for example Pele´s skin and Pele`s seaweed “limu o Pele”. These products
were named in honor of Pele. Some
people call the cooled surface above
the continuing pahoehoe lava flow
Pele´s skin, because these walls of
the lava tube can only be a few centimeters thick. Other human-like
shapes of irregular masses are called
Pele`s bones (Naiwi o Pele)1 or
Pele `s fingers. Pele`s seaweed are
curved and paperthin bubble wall
Fig.3. Pele`s tears (WEB 3)
fragments of glass. Limu o Pele is
formed when water is forced into and trapped inside lava, as when waves wash
over the top of the exposed flows of the molten rock. While boiling the water is
converted to steam, expanding to form bubbles within the lava. The lava rapidly cools and the glass bubbles burst 2. However this paper is dealing with two
other forms occuring also due to the effect of rapid cooling: Pele`s hair and
tears, which are glassy materials formed during fountaining of fludial lava in
the air3.
1
2
3
DE BOER, 2005, page 34
CLAQUE et. al., 1998, page 438
POTUZAK et. al., 2006, page 1
Pele´s hair and tears-their origin and composition
3
The origin of Pele´s hair and tears
Oftentimes Pele is shown in pictures in connection with the violent interaction of
water, lava, and explosive eruptions. But typically Hawaiian eruptions are the
calmest of the eruption types. The type of eruption and also the type of volcano
depend on the gas content, the magma temperature and the composition of the
magma. Hawaiian magmas are among the hottest on earth. Temperatures of approximately 2.200°F (1204°C) have been measured in molten lava (Kilauea, Hawaii)4. Therefore Hawaiian eruptions are characterized by gentle emission of very
fluid lava with less gas contents. Compared with other eruptions, the hawaiian
type is less explosive and the relative volume of ejected pyroclastic material is
lower. The gas escaping at the vent forms huge clouds5. The most impressiv attribut of hawaiian-style eruptions are their high (tens-to hundreds of meters) lava
fountains, which shoot into the air, while magma rises up. Clots, which rise within
the fountain, are generally still hot and incandescent when the fall back to the surface and can accumulate to form lava flows. These lava flows are about 30 feet
(9,14 m) thick. Long series of eruptions can build masses of lava flows downslope
around the vent. Small hills are called lava shield and large, broad ones are called
shield volcanoes6.
Fig.4. Shield volcano (HAZLETT, 1996)
In Figure 4 you can see a cut through a typical Hawaiian shield volcano. While
shield volcanoes stand above hot spots they grow rapidly and their mounds can
enlarge to have tens of miles in diameter.
Observations show that lava fountains occur in short spurts or can last for hours.
Under certain conditions scoria and spatter is formed and accumulated downward.
The basalt can quench into a recitulite (glassy rock) during periods of high vesiculation. But the smallest pyroclasts carried downward are Pele´s tears. During high
winds they drawn out to form long filaments called Pele´s hair7.
4
5
6
7
HAZLETT and HYNDMAN, 1996, page 13
MACDONALD et.al., 1983, page 9
PARFITT, 1998, page 197
CAMP, 2006
4
Diana Oettel
Natural Glass
Basaltic glasses are of interest as they are the major constituents of many products
(e.g. Pele`s seaweed and recitulite) from basaltic volcanism. Minerals in general
have regular geometric arrays. But glasses originates from magma with such a
high cooling rate (shown in the Figure 5), that the atoms in the melt can not organize in a crystal lattice8.
Fig.5. Cooling rate of Pele´s hair (GÖTZE, 2008)
Instead it forms a viscous amorphous glass, which can be explained as a solution
of elements. These elements are for example Al, Si, O, Ca, K. Because glass is
formed under special conditions it is metastabile near the surface, and Calcium
and potassium get lost first. Furthermore the glass starts to recrystallize into more
stable minerals. Thats the reason why most of the glasses are only of the cenozoic
age. As shown in Figure 5 different kinds of natural glass are formed under special
conditions. Pele´s hair generates by cooling down from a very high temperature
with the highest cooling rate. Other glasses produced by some lightning strikes
(Fulgurite), by frictional processes in fault zones, burning of underground coal and
impact of large meteorites have either lower temperatures or cool down more
slowly. Fast chilling of magma during building of basaltic ash cones can result in
the formation of the brown glass sideromelane9. Furthermore rhyolithic glass (>
69% SiO2) is particularly widespread because of the high viscosity of silica melt.
An example is Obsidian. While rhyolitic glasses are grey-black, the increasing
content of Ca, Mg (decreasing Si and K) produce cinnamon-brown colors in thin
sections of basaltic glasses10. Pele`s hair is especially of interest to show the element composition of hawaiian tholeiitic melts. Two rock types represent either a
rock composition mixture of Pele`s hair and olivine or a composition of parental
magma, which seems to be the result of subtracting plagioclase and clinopyroxene
from the magma of Pele`s hair11.
GÖTZE, Angewandte Mineralogie 2008/2009, Skript 6
MCDONALD et. al., 1983, page 20
10 BEST and CHRISTIANSEN, 2001, page 22
11 KATSURA, 1967, pages 157 to 168
8
9
Pele´s hair and tears-their origin and composition
5
Pele´s hair and tears
Morphology
Pele´s tears are spherical pyroclasts, which have sizes varying from few µm to
hundreds of µm of diameter. As shown in Figure 6 (part A of SEI) their surfaces
are rough and uneven. The prevalent bumpiness and their appearance on all sides
of the tears suggests particle-particle interaction. In case of shocking during
ground impact events, one or more deformed sides would appear in a none-spherical size. As shown by the arrows in
Figure 6, small particles adhere to
the surface of the Pele's tear. They
are interpreted as sublimates condensed from gases of the plume or
small glass particles12. The hair,
shown in Figure 7 has a cylindrical
form, is 8 mm long and has a width
varying between 1-500 µm in diameter. Pele´s hair can be up to 2 m
long, but is never found complete,
because of breaking during transport Fig.6. Pele´s tear from Masaya Volcano (secin the wind or contact with the ondary electron image, JOEL 5910LV: accelerground. The hair is associated with ating voltage-15kV, probe current - 2 nA, worka “knot” in the middle and a droplet ing distance - 19 mm; MOUNE et. al., 2007)
at the end. If you assume that hairs
can be formed from stretching into
strands, than knots are maybe the
result of not stretchable crystals enclosed in the glass. If you have a
closer look at this hair, you can see
oftentimes entire and broken vesicles, which have parallel orientation
to the axis of elongation. Sometimes
you can find particles adhering to
Pele`s hair, too and these particles
may have distinct chemical charac- Fig.7. Pele`s hair from Masaya Volcano (secteristics. In this case, they have a ondary electron image, JOEL 5910LV: accelerhigh cloride content, which is typi- ating voltage-15kV, probe current - 2 nA, working distance - 19 mm; MOUNE et. al., 2007)
cal for the Masaya gas plume.13
12
HEIKEN and WOHLETZ, 1985, page 245
13
MOUNE et. al., 2007, page 245
6
Diana Oettel
Formation under certain conditions
Some experiments on ink jets produzed from nozzle were performed using different Weber number (We) and Reynolds number (Re). As shown in the following
Figure, if Re is large in comparison with We a droplet is produced. On the other
hand if We is large and Re is low a thread is the result.
Shimozuru defined Pele`s number (Pe) as the ratio of (We~Re).
We = p v 212/σI: pv 2 I/ σ (1)
Re = po v l/η (2)
Pe = We~Re = pv η/ po σ (3)
p is the density of the liquid
v is the velocity of liquid flow
l is the effective length of flowing liquid
σ is the surface tension of the liquid.
po and η denote the density and viscosity of the
liquid
Fig.8. Ink jet produced from nozzle under
different We and Re-time sequence from top to
bottom (Left:We = 20, Re = 44; Right: We =
50, Re =32); SHIMOZURU, 1994
Considering that p/ po in equation 3, velocity, surface tension and viscosity of the
liquid flow are the parameters of remainder for observation. The temperature of
the lava is involved in vicosity and surface tension. Measurements of the viscosity
of hawaiian melts show results of 87 Pa s and 48 Pa s at temperatures of 1160°C
and 1190°C (documented temperatures of Alae eruption at Kilauea). So if the
range in temperature is small, a small range in viscosity is the result. The effects
of temperature of magma on surface tension of the liquid are different. Positive
temperature derivates14 and surface tension decreases with increasing temperatures15 were determined. But at least surface tension has also not high effects on
Pele´s number. Thus, the most significant parameter is eruption velocity. To conclude: If the velocity is high- Pele´s number became large and Pele´s hair will be
produced. On the contrary Pele`s tears are formed.
Experiments with artificial glass fibre also display low viscosities (<100 Pa s)
spurting of molten silicate. To produce a high quality fibre glass a certain viscosity
of the silicate and the temperature of re-heating, the combination of flow velocity
from the nozzle and also revolving speed of the spinner16 is necessary. That means
Pele´s hair might be produced under very complicated conditions including turbulences while spurting.
14
15
16
MURASE and MCBIRNEY, 1973
KING, 1951
SHIMOZURU, 1994, page 218
Pele´s hair and tears-their origin and composition
7
Transport and Interaction
Usually Pele`s hair and tears are collected together downwind from the vent.
Due to the high spurting velocity Pele`s
hair is often carried very high in the air.
Additional strong winds can blow the
hair threads up to tens of kilometers
away from the vent. In Figure 9 you can
see Pele`s tears in the cavities of Pele`s
hair. This is a fact, which supports the
hypothesis of funnel capture during
transport in the volcanic plume. The hyFig.9. Cavity of Pele`s hair (MOUNE et.
pothesis says that cavities act like funal., 2007)
nels and samplers of tears during transport of Pele´s hair in the volcanic plume. Another argument to support this theory
is that Pele´s tears are observed in high concentrations at the bottom of the cavities. So it is possible that Pele´s hair and tears are associated due to the effects of
transport and independent of their mechanism of formation. The arrows in Figure
9 show that sublimates also adhere to the surface of the tears in the cavities, as
shown in Figure 6 (page 6).
Pele´s tears are also observed on walls
of Pele´s hair, outsides the cavities.
These walls are oftentimes very thin and
they can break easily. Sometimes these
walls are so thin, that they allow observations through the walls of cavity.
Pele ´s tears are concentrated at raised
edges and surrounding them, because
these edges form a kind of barrier during transport, so that the tears can trap.
Remarkable is that these tears have a Fig.10. Cross-section of Pele`s tear
high varity in their sizes. In Backscat- (MOUNE et. al., 2007)
tered Electron Images (BSEI) of Pele´s
tears spherical gas bubbles can be found (Figure 10). Dark material in the bubbles
is derived from polishing. The bubbles can be up to 150 µm in diameter in tears
with sizes of 800 µm). Furthermore a tabular shaped crystal of plagioclase is
linked to the gas bubble. Remarkable is also the chemical zonation rim of this
droplet17, which is between 6 and 10 µm broad.
17
MOUNE et. al., 2007, page 246
8
Diana Oettel
Chemical Composition
Fig.11. The total alkali-silica (TAS) diagram showing three
analysis of Pele´s hair and one of Pele´s tear (modified after Streckeisen et. al., 1985, complete chemical data see Appendix)
Figure 11 displays three analysis of Pele`s hair and one of Pele`s tear, which are
plotted in the TAS-diagram. They all have a basaltic composition and you can see
that Pele`s tear (the point in the top right corner of the Basalt field) has a different
composition, while Pele´s hairs are
more similar. Pele`s tear is from Masaya Volcano (Nicaragua) and Pele´s hair
from Kilauea (Hawaii) and actually not
comparable. But what I want to show
is, that both, Pele`s hair and tears, are
basic (contain 45 an 52 wt % SiO2).
The composition Pele´s tear in Figure
11 is the result of an average taken
from measurements of the inner part of
the tears (between 10 µm and 30 µm,
shown in Figure 12). Furthermore mea- Fig.12. Chemical zonation rim (MOUNE
et. al., 2007)
surements of the outer part of the tears
were also taken. A strong chemical gradient in concentration of the major elements was measured comparing the outer part and the inner part of the tears. At a
distance of 2 µm and 6 µm a much higher SiO2 content was observed. The average
of analysis represent lower SiO2 content and small variation in the inner part of the
tear18.
18
MOUNE et. al., 2007, page 247
Pele´s hair and tears-their origin and composition
9
The major element totals are normalized at 100%. In the outer zone of the tear the
major element totals are too low. In contrast, the totals of the analysis in the inner
part of the tear are much higher (97–98%) and homogeneous (Figure 13). The
sums of the analyses 1 and 2 (86 to 88 wt.%) performed in the outer zone are
maybe a result of the high volatile content in the tears suggesting that the Masaya melt was not totally degassed while erupting. The chemical variability from
the tears' interior to its rim display increasing silica enrichment and decreases
when all other elements increase.
Fig.13. Compositional profile along the line of measurements
(MOUNE et. al., 2007)
Pele´s hairs also contain euhedral plagioclase crystals and chemical zonation
around the external part. Chemical zonation can also be found in cavities on their
internal walls along Pele´s hairs. The thickness of silica enrichment at the cavity
walls inside and outside is constant. Some tears inside these cavities display
chemical zonation, some have no zonation and others are transformed.
Furthermore along-axis sections of Pele´s hair show spherical and curved sizes,
so that they are not always elongated to the hair axis. This variations can be observed on the same hair19. So a complex formation of Pele´s hair can be assumed
(compared with page 7).
19
MOUNE et. al., 2007, page 249
10
Diana Oettel
Conclusion
Pele´s hair and tears are fundamentally composed of glass, and that infers a rapid
cooling in the eruptive plume. These pyroclastic materials are unique, caused by
their formation including rapid quenching and exceptional high temperatures of
magma resulting from fountaining of hawaiian-style eruptions. The fact that cavities in Pele´s hairs act like funnels of Pele´s tears displays that they are associated
due to the transport and formation. The most important parameter, which decides
whether a droplet or a hair is formed is the spurting velocity. If it is high Pele´s
hair is formed, it not Pele´s tears are the result.
The glass of Pele´s tears also contains euhedral plagioclase crystals. That shows
that the magma was not super-heated and cooling was rapid as these crystals do
not expose dentritic overgrows. The plume temperature was probable below the
glass transition temperature. This is a supposition made because of the absence of
devitrification textures. Vesicles in tears and hairs suggest that the magma was not
totally degassed at the eruption-time. Pele`s tears seems to have a general concentration of volatiles between 2.9-1,9 wt.% 20.
Another community of Pele´s hair and tears is the chemical zonation rim. This
rim is best explained by dissolution of silica glass during interaction with volcanic
gases in the plume and potentially a important chronometer of residence time in
the plume21. Alteration by rain water is not likely because samples were collected
immediately after eruption. Furthermore the Silica enrichment is not connected
with enrichments in Al and Ti, which should be the effect of different mobility of
network forming and modifying cations22. After all the scenario of forming Pele´s
hair and tears can be decribed as the following:
At the beginning of the eruption the spurting velocity is high during fountaining
at the top of the conduit. Pele´s hair is formed. Vesicles obsevered in Pele´s hair
have parallel orientation to the axis of elongation of the hair. This is a result, if
these vesicles are deformed with regard to direction of magmatic gas jets. Later,
when the spurting velocity is decreased (the fountain might be less high), but the
temperature is still high enough, that Pele`s hair stays in liquid state, gas exolution
produces sperical vesicles. Furthermore Pele`s tears are produced at this time, bacause they contains only spherical vesicles. No stretching is associated with the
formation of Pele´s tears. This result is consistent with the model, saying that
Pele`s tears are produced when spurting velocity is low. Before the ejection, there
are several turbulent mortions inside of the eruptive plume at relatively low temperatures included in this model. Thats a suggestion based on the fact that no devitrification textures are observed23.
20
21
22
23
DEVINE et. al., 1984
MOUNE et. al., 2007, page 250
STERPENICH and LIBOURAL, 2001, pages 181-193
MOUNE et. al., 2007, page 251
Pele´s hair and tears-their origin and composition
11
References
BEST, Myron G.(2001); Christiansen, Eric H.: Igneous Petrology. Blackwell Science, Inc. Press: page 22
CAMP,Vic(2006), Department of Geological Sciences, San Diego State University, link:-www.geology.sdsu.edu/how_volcanoes_work/Hawaiian.html
CLAGUE, D. A.; Davis A.S.; Bischoff, J. L.; Dixon, J. E.; Geyer, R.(2000): Lava
bubble-wall fragments formed by submarine hydrovolcanic explosions on
Loìhi Seamount and Kilauea Volcano. Springer Verlag, Bull Volcano
61:437-449: page 438
DE BOER, Jelle Zeilinga; Sanders, Donald Theodore(2005): Volcanoes in Human
History. Princeton University Press: page 34
DEVINE, J.D., Sigurdsson, H., Davis, A.N., Self, S.(1984): Estimates of
sulfur and chlorine yield to the atmosphere from volcanic eruptions
and potential climatic effects. Journal of Geophysical Research 89, 6309–
6325.
GÖTZE J.(2008/2009), Angewandte Mineralogie, Skript 6
link:-www.mineral.tu-freiberg.de/mineralogie/mintech/lehre/lehrmaterialien
HAZLETT, Richard W.; Hyndman, Donald W.(1996): Roadside Geology of Hawaii. Mountain Press Publishing Company: page 13
HEIKEN, G., Wohletz K.(1985): Volcanic Ash, University of California press,
Berkeley, California: page 245
KATSURA, Takashi (1967): Pele´s hair as a liquid of Hawaiian tholeiitic basalts.
Geochemical Journal, Vol. 1: pages 157 to 168
KING, T.B.(1951): The surface tension of silicate slugs. J Soc Glass Tech 35:
241-259.
MOUNE, Séverine; Faure, François; Gauthier, Pierre-J.; Sims, Kenneth
W.W.(2007): Pele`s hairs and tears: Natural probe of volcanic plume.
Journal of Volcanology and Geothermal Research, Vol. 164 issue 4: pages 244 to 253.
link:-ftp.whoi.edu/pub/users/ksims/public_pdf/Moune et al_2007.pdf
MURASE T.; McBirney A.R.(1973): Properties of some common igneous rocks
and their melts. Geol Soc Am Bull 84: 3563-3592.
12
Diana Oettel
PARFITT, Elisabeth A.(1998): A study of clast size distribution, ash deposition
and fragmentation in a Hawaiian-style volcanic eruption. Journal of Volcanology and Geothermal Research 84: pages 197 to 208
link:-www.sciencedirekt.com
POTUZAK, M.; Dingwell D.B.; Nichols A.R.I.(2006): Hyperqueched Subarial
Pele`s hair Glasses from Kilauea Volcano, Hawaii. Geophysical Research
Abstracts, Vol.8, 06908: page 1
SHIMOZURU, D.(1994): Physical parameters governing the formation of Pele's
hair and tears, Bulletin of Volcanology 56: pages 217 to 219
link:-www.springerlink.com
STERPENICH, J., Libourel, G.(2001):Using stained glass windows to understand
the durability of toxic waste matrices. Chemical Geology 174: pages
181–193.
List of Figures
Figure 1: Pele- goddess of fire and volcanoes
WEB 1: www.solcomhouse.com/images/peleherb.jpg
Figure 2: Pele´s hair
WEB 2: http://geology.about.com/library/bl/images/blpelehair.htm
Figure 3: Pele´s tears
WEB 3: http://www.swisseduc.ch/stromboli/glossary/peletears-en.html
Figure 4: Shield volcano
HAZLETT, 1996. page 13
Figure 5: Cooling rate of Pele´s hair
GÖTZE, 2008
Figure 6: Pele´s tear from Masaya Volcano
Figure 7: Pele`s hair from Masaya Volcano
6, 7:MOUNE et. al., 2007, page 246
Figure 8: Ink jet produced from nozzle
SHIMOZURU, 1994, pages 217 to 219
Figure 8: Cavity of Pele`s hair
Figure 9: Cross-section of Pele´s tear
Figure 10: Chemical zonation rim
8, 9, 10: MOUNE et. al., 2007, pages 247-248
Figure 11: The total alkali-silica (TAS) diagram showing three analysis of Pele`s
hair
and one of Pele´s tear modified after Streckeisen et. al., 1985
Figure 12: Chemical zonation rim
Figure 13: Compositional profile along the line of measurements
12, 13: MOUNE et. al., 2007, pages 248-249
Pele´s hair and tears-their origin and composition
13
Appendix
Pele`s tears
Pele`s hair
1
2
3
50,9 (0,6)
48,82
50,26
50,04
TiO2
1,42 (0,13)
2,77
2,69
3,02
Al2O3
13,5 (0,4)
13,8 (0,4)
0,25 (0,08)
4,67 (0,14)
8,81 (0,30)
13,42
9,9
0,18
9
11,32
13,48
9,57
0,17
7,04
11,45
14,02
9,45
0,17
6,93
11,45
2,83 (0,18)
2,25
2,22
2,42
1,39 (0,13)
97,6 (0,8)
0,58
100,22
0,45
99,96
0,57
100,24
SiO2
FeO
MnO
MgO
CaO
Na2O
K2O
Total
Pele´s tears: Masaya Volcano (Nicaragua)
MOUNE, Séverine; Faure, François; Gauthier, Pierre-J.; Sims, Kenneth
W.W.(2007): Pele`s hairs and tears: Natural probe of volcanic plume. Journal of
Volcanology and Geothermal Research, Vol. 164 issue 4: pages 244 to 253.
link:-ftp.whoi.edu/pub/users/ksims/public_pdf/Moune et al_2007.pdf
Pele´s hairs: Kilauea (Hawaii)
KATSURA, Takashi (1967): Pele´s hair as a liquid of Hawaiian tholeiitic basalts.
Geochemical Journal, Vol. 1: pages 157 to 168