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,**3  1 : +. ; ,**3  +, : ,, ;Re-activation Process of Showa Volcanic Vent at Sakura jima Volcano in ,**2 :Evidence From Volcanic Ash
Isoji MIYAGI, Jun’ichi ITOH, Hiroshi SHINOHARA and
Kagoshima Observatory, Japan Meteorological Agency
We describe reactivation processes of the Showa volcanic vent at Sakura jima volcano, Kagoshima, Japan.
The Showa volcanic vent is located on the east side hill of Minami-dake summit vent at Sakura jima volcano.
While Minami-dake summit vent has been active intermittently for the past ﬁve decades, the Showa volcanic vent
was dormant for an interval of about /2 years until . June ,**/. Ash samples analyzed were obtained fromvolcanic explosions of both Showa and Minamidake summit vents from +32+ to ,**3. The analyses andobservations on the volcanic ash samples include (+) amount of water soluble chlorine and sulfur adsorbed on
volcanic ash particles, (,) mineral identiﬁcation using X-ray di#raction patterns, (-) color measurement, (.)
simpliﬁed particle size analysis of volcanic ash, (/) micrographic observations of ash particles using an opticalbinocular microscope and a SEM, and (0) chemical analysis of minerals and glasses in ash particles with an
EPMA. (+) and (,) suggested that the proportion altered/non-altered blocky particles in volcanic ash from theShowa volcanic vent was decreased from ,**2 to ,**3. (,), (-), and (/) indicated a gradual increase intemperature of the vent with time. We regard (+)-(/) features as results of a gradual reactivation process of the
Showa volcanic vent since . June ,**/ by May ,**2.
Key words : Sakura jima, Volcanic ash, Backscattered Electron Images, XRD, Volcanic gas+ῌ ῏ ῍ ῐ ῎<=5 >+,+-?@7 A'BCDEF$

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Kagoshima observatory, Japan Meteorological Agency
Geological Survey of Japan, Tsukuba Central 1, +ῌ+ῌ+Higashi, Tsukuba, Ibaraki -*/ῌ2/01, Japan.
Corresponding author : Isoji Miyagi
e-mail : miyagi.iso+.***@aist.go.jp

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26

Table ,.

Fig. ,. Water soluble chemical components of volcanicash (,**0ῌ,**2). (a) Concentration of chlorine andsulphate ion (mg/kg). (b) Ratios of chlorine andsulphate ion (mol). All the plotted data are fromash samples from Showa volcanic vent, except for asample (IDSakura,**2 *.,2) which is a mixtureof those ash from Showa vent and Summit vent.

-.

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Amount of water soluble F, Cl, S.

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Fig. -. Collection of X-ray di#raction patterns (cps over ,q). (a) X-ray di#raction patterns ofHydrophobic very ﬁne particles which was ﬂoated on water surface during ultrasoniccleaning of ash samples. (b) X-ray di#raction patterns of ﬁne particles suspended in water
for longer than + minute after the end of ultrasonic cleaning of ash samples for about -*minutes and recovered by overnight heating at 3*. Condition of X-ray di#raction analysis
is described in the text.

27

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28

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894:BbwQxTc=

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RST­S Fig. + 8],"®ῐ8[\]^I(
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Fig. .. Color of volcanic ash plotted on a*-b* system of
CIE L*-a*-b* color space. The CIE L*-a*-b* color
space was described in the second Commission Internationale d’Eclariage (CIE) +310, and the values ofa* and b* correspond to the intensities of red (a*)and green (a*), and yellow (b*) and blue (b*)color, respectively. (a) Color of bulk dry volcanicash. Open circles represents ash samples from +32+
to +33+, all of which were derived from the Summit
vent of Sakura jima volcano. Solid circles are
samples of the beginning of ,**2 activities from February to ++ April, and solid triangles are thosefrom the succedent activities after ,2 April. A
straight arrow indicates a possible color change trendof a mixture of color less powder and native sulfur.
A curved arrow shows an observed change in colorof heated volcanic ash in air (Miyagi and Tomiya,,**,). (b) Comparison of the color of dry bulk
volcanic ash (dots) with those of dry ﬁne particles(solid circles for samples from -* May ,**2 to +*March ,**2, open circles for those from ,**0 to +/May ,**2, and open triangles for those from Minamidake Summit vent from +32. to +33,) recoveredfrom murky water after ultrasonic cleaning of bulk
ash samples for about -* minutes.

 ,**2
Table -.

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Average value of Color measurements.

29

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Horizontal axes represents diameter of ash particles
in f scale (,-f, mm), and vertical axes shows
cumulative weight of particles (ῌ). Particle size
distribution was analyzed according to weight ofparticles on sieves and weight di#erence of ash
before and after the ultrasonic cleaning with water.
Dashed thin lines represent for samples from Minamidake Summit vent from +32. to +33,. Thin lines
represent for those erupted from - February to 2
May ,**2. Thick lines are those from +/ May to+* July ,**2. Dashed thick lines are those erupted
after ,1 Jan ,**3.

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E2_2OP!°°%T) (Fig. /)

[2\«¬501­®¯2'$?/4O$r.

-ῌ/ ῌ῎ῐ῍) tu8   (,**3) 2)

,**2 2D9EO +32*3* d2:N9E29:*f/ Blocky particle C+) Glassy particle;2±l8 ²0 ¢I³2& ~´µ   3 ?n 01 ?!

) 2¦

 (Fig. 0 b,

% ¡,-./& ¬5«¬5201-/8¶

Table .) 8 +32* d2:N9E29:;

Z·9:­®¯& [?! &orI)O L*.*- or *.*/ O¸!8%8¹?! )$ ±l2'8ª] 6$T.C? ,**2  2D  9E29:;%8 , F$ *.2 )  29%J)~º ]^¯»¼Y

*.3 O½ $ ]^OO_ S$? 1 F ,2 $

+323  2 F2 *./0 (n 4267 8,**2  9:2; <* =

31

2  +.. *.,   / !

+/ -* *./ *.-   1 !

+* ,2 

*., *.*2  

-ῌ0 
+32.  ,**2 267>

./0&?@A1  (Fig.

1) Ti, Al, Ca, Mg, Mn, Fe, K, Na

BCDCEF

267GH)./0IJ KLML

&?

@A +32*3* NO ,**2 PO QR
ST ( )SU

(Fig. 1aῌh) 9 VWV

XY&?@A FZ[ ,*** \Z]^PO_PO`aS bc ,**/ Ti

BCDC

EF267 ./0&?@A'5
bc (,**/) 'd,*** \Z]^P X

Y&?@A &ef gh] ,*** \Z]
_P

gi



j) (Fig. 1a) k l>m`n 8o (Altered part)&?@A ,*** \Z] _P gih NOpq)Lr./0Os./0&?@At Table / d5. 

.ῌ+,**2 :2;

Pu)

267

!vwx

"#$%&' ( ) * +, - 
Fig. 0. Temporal change of ash constituent. Ash particles, sieved, mounted, polished and photographed(Miyagi and JMA, ,**3) are classiﬁed into four
categories according to their brightness and microtextures in backscattered electron images ; Altered(dark particles), Blocky (moderately bright particles
with numerous groundmass minerals and enclosed byfracture surfaces), Glassy (moderately blight to slightly
dark glassy particles with bubbles), Etc (crystal
fragments and the rest of particles). (a) Temporalchange of Altered/Blocky particle count. Arrows
represent the sequence of eruptions. (b) Temporalchange of Glassy/Blocky particle count. A superimposed ﬁgure shows the long-term data including
Minami-dake summit vent.

%QOy  z zO 2;{`|Au)} ~" tOo )
 :2; P A>  $%&']  h  + 2* ` Pu)
267}Y ' 1-GH)' 2'345 )}Y 5 z  %QOO 2# } ~"' zOt$5 H 267

X iZ) %

}&SJ L'!  ,**0 ,**2 

 [

%Q

OO ( z)



*

t<¡ :2;)¢ 2#*F 26.
0 +Z%}£, ¡¤O¥¦ FZ§%}JtG¨-Y'2 a}Y O Pu

 *.*2 H`.¢+..- ©  /0)zO`ª1u) zOt5Opq) 

./0}Y  «  2 2* F/ ! 1 2#* ¬3'h­5zOZ]%}J 1®%Q0¯C°4` &' ( ) 
h  + 2* ` Pu) 267
./0 ' 1-  2'345 )5;o ,**2  . ! - . z*.-- 

(Fig. 0b) /0 / ! 1*.,3 ^»¶



|A5'.¢7u) )S SF 6±²`³,**0 O ,**1  ´8 #A'S

9: [)µ) %, 2 2 , Pu)
267t·¸¼½`RS

(¹Opq)' ´8<º`

32

Table ..









!"

01 Zimanowski et al., +331 

Result of particle counting.

#$%&'()!%&' *++!,-./%
.ῌ,  

23,4!

.ῌ,ῌ+ 

)565789:;<= >?"@A*%+32+  +33, 2HF:&'IJ/KF

LMNO>?28P)3*QRSJ/%&'

BCDE% (&(+D' FGGTUVW a*ῌb* XYZ[ (Fig. .a) \27!

]DAE% ,**2,**3 2^ :&'IJ)_*D! ,.1 A`a""% b/c# ,***

/KFGd$ 2 e +2 %FG"f&Ag'hi(KjW(i +32++33, F:3,)k)l*+2,AE% (Fig. /) m-.

 +32++33, FGd$D$k)p2Aq#,HFGW(iXYrsDtu,v0

wJ/KKx 8yIz2{!H2AqwJ/K

,|}(K~"27%565 3Q27!

32)k)MDuKx,v0'/% 1 A

):&'IJ/K4LFG  ~(i(KFGd$ qw",I&5N" FGW23,4!)6$%

7&'5D8AE%&' LM 3

/  ,**, ,0nAE% mbA1oA c+32+  +33, 2HF:&'IJ/KF

8u,v0'/% m/'d$)2!)M"

GW"2,%, ,**2  ,. eFG

%

:;+2

"6$%b,9AE%&':427%565N?<  "W

789 <=W">9)!%

2(Fig. .a) W@"x%,() X 3,4!)@$%b,x)7Q AB (A CD¡D¢J/%b,&' £¤2¥¦§ W ¨© iª EF2 

«/%



C28%BW"¬­%b,DA*%D,;®DGx'/+! b¯ °D¡()!K

Fig. .a ±Hu&' ,=²IJ"³KA*+

,;®DL8+M 28P)´! FG2=WW"I0%,() FG

J/Kb,"]@$%&3(/+!D °,;®DL&PKBC3M6A*+! · 
(i"Lº()@$%D 1 AJ/K
FGd$ ,f ·¤©"½O,$%EFDt

2µ!W"I0%XYrs hi ,¶2 hi"
N¸$%¹'&XYrsDv0'/%
,**2,**3 H^ :FG ¦N»¼

siª

N¨©§PD +32*+33* Q3



,**2 

33

Fig. 1. Chemical composition of ash particles including fragment of phenocrysts, matrix glass, and glass inclusions inphenocrysts. Open circles represent ash samples erupted from Minami-dake Summit vent from +32. to +33+.
Gray transparent circles are those erupted from February to July ,**2. Analytical ﬁgures are normalized to be
dry and +**ῌ bases. Horizontal axes represent SiO, wt.ῌ. Vertical axis of plot “a” is TiO, wt.ῌ. Two ﬁlled
regions in plot “a” represents whole rock chemical composition data from Uto et al., (,**/) for those samples
younger or older than ,*** years (noted as “,*** yrs” or “ ,*** yrs”, respectively). Vertical axis of plot b,c, d, e, f, g, h are Al,O-, CaO, MgO, MnO, FeO, K,O, Na,O, respectively.

 !"#$%

34
Table /.

Examples of EPMA results for matrix glass and melt inclusions.

&'()*+,-&. /&012345678
9:-6;< 45&012=>#? fO, '#@A

Table 0. Schematic classiﬁcation of the e#ect of t, T,
and fo, on color of valcanic ash.

B .CDE3FGHI&JKLE&MN OP
OPQR-< , S&LT@:U9VW.(X  ,**,  (low, high)  (short, long)&YZ[&\@]B^X 012&JLE_`ab3. S&cdb@[e.(X (Table 0) ,f 012@g

hiXjJ&L5klN mnop9-XJK&LE@
N'(,qr3s8,-78H &YZ[&
high @Ntuv&w1x

yzw1x5{|{& (2** +*** ) 3 low @N012=DEp,),
X3}B^X  low&~N  &,***  2  +2 012.N ,**-**,**, xZ&y&.N .**78 short @N: -3}B^X 

Table 0 &cdb (+) N '#^Xv@{|.{&=p9-XM.X Table 0 &cdb/**

X (Miyagi et. al., +332) OP&YZ[ long @N(-) 5@N4 p9{|{=&C),>#?.OPiH012&J&LE=,-x@ &¡-x¢p9£¤pHM¥ !¦

XT +* T +** [ ¨©p9tupH:<,M=ª«¬iX tu­@'  ,**, :§-3%&'( ,**2  )  *+ ,35-#./0 %&123/45 6744(%& 8 9:;<=$126>

5?@A Table 0 (Fig. . b) 8BC (,)  DE FGF -BC K<=$123/3/( H!"6IJ6> #(,)

L!" FGF MN/ O BC612

5 -# (DE FGF12#PQ# $ BC (+) (-) (.) K

4%R ST&' > (U DE%&V!SO=

)*+ T48 <=W512

12X!" ,3 %&V P-.<X(#YI/ Z/ <A %& [ \0T4]^_`a7=I.b1  E. !"##$/2 (O %&<A(c (,x)

 48#d (

4V5L ef -#34g56. + *.+ mm .

,**2  /8 .!" (t  x / D)  i 9

3 jk : D  *.*+,

Zh # +32*3* %7

#6 _H DE?@A +32*3* %(cm,/sec) #./0 (Clark, +300) *.,/ ;,./ lm;7 %&$ 8 <=$123/..no c<P!" p<q6T^_ (,)

*., ;. =35( aL r %&V&#s(>t uv3/ a* <w b*x

E. r E.-y?z.o6>

@$^{$|6> (Fig. .b) zaL ,**2  /Zhr E. "E -A}=~O##B3

BC6>= ,**2  /Zh % E. +32* %7#$.

CD#<aLE. FGHI JK (

D5 LM >  %7I645

 N</0 (rOZP

?@A

QA

a

#O@6 RS  jk% T,W.UL BC (,) 12%R V!"OZ (#IRS  2\6>a(# L?#YI/ O V!" -633/($ RS .<aL$W2. Barron and Torrent,

%&

-#J



L5<A'I

!"W2

(

XYH#4O +* O +** +320 ; Kubelka and Munk, +3-+)  ( 9:;%Z [ ,**, <=$5 %&\&#8# "'/( 5  ].

412Xo6> S %&5% L5 LM$>

V AH )*+ T48V <=12XL

%&[ L 9:; #^R23/($|2.#YI/ Table 0
FGF# #BC (.)  DE

07%R (U.J6>

LaP-bc.J

 %R!" > 8V
V$12g#¥¦/ Z/

 4 )%& ^{$|6> (Yamanoi et al., ,**2)
 5_|3(48.`Z>#MN/YIL<5?@A %&V.4V#4o

84V#6d 12¡¢ef £4¤  h$#§5

W2 4¨?#YIL3 ©I45?@AL %& 9:; # %&i (8.ῌ,ῌ-  # .O#<=  E.y+32*  3* )%73/(%jIFGF P kGlm[.Yª&^«no 5 p¬_­®45 O/¯4A 4 Table 0  ,**2  ,.

BC (+)(.) qo $rs647 BC (.)

s BC/tT.

LM >vw± q86>
,**0  ,**2  / +32* 3/(%& 8#9:;  Jx L= c<o¡¢4{. (Fig. .b) c<o12
XL545O# Table 0K o (+) # (-)
O ,**-**BC (,) # (.)-b) O ²ª¤³ ,**2  ,.

5L 9´ «n2yI Q# z5(¤d
L5 |}

­{A µ!W2    !"##$ +32* %7 $ hs LT(O#d· L5

EE%& 

%&­®/ A ~°  _Z++ ¯4¦/(3N²</0 º»4DE

/L545

½   ,**2
,**2  /%7#^{$A#4a( (Fig. 0

K . zaL O !¶E.Ea(O# d·3/ ³¸ ,**2   QA­   A!"##$°u  ,**2  1

Zh ,**3 <A4

5%

L5

?@A )

5Lx¹ ,*** "5LFGF
T4W 45 Fig. 1a <w¼2`s ,**/FGF 9:;2` $|J 34gef
3/

FGF «n. :v E.#­GA E



36 

!"#$ ! %!&  '(')* +,-./&06789:;<%  =>?
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3&!51@1! !51 
F<'(&4 

GHI ;"JK+,-J&)LM NOIP* +G<& DE%&)L<

ABA,-.?/ 0MQ1 2R2&'(9S T;"U3&VW

4!W ;"%Z 4X< (Cashman and Blundy, ,*** ; Suzuki etX9,-.?YO6ABA?MQ [ %\,-J&'(94 (Dingwell, +330)

al., ,**0 ; Swanson, +311) ]6 ABA56^78

_9RH21  ')* ^] +,-.`:

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94Fl

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A& 65'`a1 I3M 6 '6

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37

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38

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6@7z-=$¡I¢¨ =$AB8C9 ,**2 = P., +-.p.
Anderson, O.L. (+312) The role of magma vapors in volcanic tremors and rapid eruptions. Bull. Volcanol., .+,-.+ῌ-/-.
Barron, V. and Torrent, J. (+320) Use of the KubelkaMunk theory to study the inﬂuence of iron oxides on soil
colour. J. Soil Sci., -1, .33ῌ/+*.
Cashman, K.V. and Blundy, J.D. (,***) Degassing andcrystallization of ascending andesite and dacite. Philos.
Trans. R. Soc. Lond. A, -/2, +.21ῌ+/+-.
Clark, S.P. J. (+300) Thermal conductivity. In Handbook ofphysical constants. Geol. Soc. Am. Mem., 31, .0*ῌ.2,.
Dingwell, D.B. (+330) Volcanic dilemma : ﬂow or blow?.
Science, ,1- +*/.ῌ+*//.
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B,0 12p.
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8C9 ,**2 = P-2 +-*p.
Kazahaya, K., Shinohara, H. and Saito, G. (+33.) Excessive degassing of Izu-Oshima volcano : magma convection in a conduit. Bull. Volcanol., /0, ,*1ῌ,+0.
²³±} ´² (,**2) ³´µvw7DcSM ¶µ=#j{¥=#=$ ¶··¸¸3
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Koyaguchi, T. (,**/) An analytical study for +-dimensional
steady ﬂow in volcanic conduits. J. Volcanol. Geotherm.
Res., +.-, ,3ῌ/,.
Kubelka, P. and Munk, F. (+3-+) Ein Beitrag zur Optik
der Farbanstriche. Zeitschrift fur technische Physik, +,,/3-ῌ0,*.
aP$AQbcdR (,**2) S +* e-=$9Tf@7 '/ +3 = 0 g'/ ,* = - g aP$AQb
cdRZ[=$o\cd\p
Mangan, M. and Sisson, T. (,***) Delayed, disequilibrium
degassing in rhyolite magma : decompression experiments and implications for explosive volcanism. Earth
Planet. Sci. Lett., +2-, ..+ῌ.//.
Melnik, O., Barmin, A.A. and Sparks, R.S. J. (,**/) Dynamics of magma ﬂow inside volcanic conduits withbubble overpressure buildup and gas loss through permeable magma. J. Volcanol. Geotherm. Res., +.-, /-ῌ02.
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   (,**,) W=$Rl : ¡=$ ,*** = 2 g +2 =$¢c =$ .1 1/1ῌ10+.
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=$RKYi BTf\pcd£U
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Miyagi, I., Yurimoto, H. and Takahashi, E. (+331) Water
solubility in albite-orthoclase join and JR-+ rhyolite melts
at +*** and /** to ,*** bars, determined by microanalysis with SIMS. Geochem. J., -+, /1ῌ0+.
Miyagi, I., Matsubaya, O. and Nakashima, S. (+332)
Change in D/H ratio, water content and color during
dhydration of hornblende. Geochem. J., -,, --ῌ.2.
Nakamura, M. (+33/) Continous mixing of crystal mushand replenished magma in the ongoing Unzen eruption.
Geology, ,-, 2*1ῌ2+*.
Ryan, M.P. (+321) Neutral buoyancy and the mechanicalevolution of magmatic systems. In Magmatic processes :physicochemical principles (Mysen, B.O. ed.), Geochem.
Soc. Special Publ., +, ,/3ῌ,21.
Suzuki, Y., Gardner, J.E. and Larsen, J.F. (,**0) Experimental constraints on syneruptive magma ascent related
to the phreatomagmatic phase of the ,*** A.D. eruptionof Usu volcano. Japan. Bull. Volcanol., doi +*.+**1/s**../-**0-**2.--.
Swanson, S.E. (+311) Relation of nucleation and crystal
growth rate to the development of granitic textures. Amer.
Mineral., 0,, 300ῌ312.
, ¤ (+33.) °¬B­®Oy¯ °Li BA±9 .- +ῌ+3.
Takeuchi, S. (,**.) Precursory dike propagation control ofviscous magma eruptions. Geology, -,, +**+ῌ+**..
¹Pº¡¹»$±Hoang NGUYENº¼»$¼½¥½ (,**/) -=$A./

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Yamanoi, Y., Takeuchi, S., Okumura, S., Nakashima, S.
and Yokoyama, T. (,**2) Color measurements of volcanic ash deposits from three di#erent styles of summit
activity at Sakura jima volcano, Japan : conduit processes
recorded in color of volcanic ash. J. Volcanol. Geotherm.
Res., doi : +*.+*+0/j.jvolgeores.,**1.++.*+-.
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Zimanowski, B., Buttner, R., Lorenz, V. and Hafele, H.-G.
(+331) Fragmentation of basaltic melt in the course of
explosive volcanism. J. Geophys. Res., +*,, 2*-ῌ2+..
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