ῒΐ  /,  (,**1)
 +  +ῌ,+ ῕ ῔῔ῑ῎ῒ῍῏ῌΐ῍ῐ   ,**0  .  ,/  ,**0  +,  0 Eruptive History of Ohachi Volcano, Kirishima Volcano Group, Southern Kyushu, Japan
Masaaki TSUTSUI῍, Mitsuru OKUNO῍῍ and Tetsuo KOBAYASHI῍῍῍The Kirishima Volcano Group is composed of many Quaternary volcanoes occupying an area about 0** km,.
Ohachi Volcano is a small, active stratovolcano situated at the southeastern part of the Kirishima Volcano Group.
It has a considerably large crater compared to the size of its volcanic ediﬁce, with thick agglutinates that crop out
on the wall of the crater.
We studied the eruptive history of Ohachi Volcano by tephrochronological method, and recognized +/ tephra
deposits around the volcano. Geological and archeological data and documentary records of eruption indicate thatthe oldest tephra from the Ohachi Volcano is the Araso tephra (AsT) erupted in ca. AD 1**. All other tephra
deposits were erupted in historic time such as Katazoe tephra (KzT) in AD 122, Miyasugi tephra (MsT) in ca.
AD +***, Takaharu tephra (ThT) in AD +,-/, and Takachihogawara tephra +-++ (TgT-+ to TgT-++) in the
period of AD +,/*-+1**. Thus, the Ohachi is a very young volcano at +-** years old.
We recognized two types of magmatic eruption : sub-plinian and vulcanian. Lava emission took place at least
four times in association with sub-plinian eruptions. Among these eruptions, ThT is the most voluminous, and apyroclastic ﬂow was also generated. The total volume of erupted magma (volcanic ediﬁce included) was calculated
to be about ,./+*2 m- (DRE). Eruption rate was not constant throughout the eruptive history of Ohachi
volcano, that is, the eruptive history is conveniently divided into three stages by the eruption rate : the early stage
from AD 1** to +,-/ (ca. /.* years), the middle stage from AD +,-0 to +1+1 (.2* years), and the late stage fromAD +1+2 up to present (,3* years). This indicates that more than 2*ῌ of the total amount of magma wasproduced in the early stage, while the remaining ,*ῌ of magma was erupted in the middle stage. Although there
are many recorded eruptions during the late stage, it is di$cult to ﬁnd any tephra deposits around the Ohachi
Volcano, which suggests that the scale of volcanic eruption is progressively diminishing through time.
The volcanic ediﬁce of Ohachi is composed mainly of succession of thick tephra layers, some of them changed
to agglutinates. Correlation of the proximal deposits to the distal tephra suggests that the volcanic ediﬁce hadgrown mainly during the two eruptive stages of KzT and ThT, which are comparatively large-scale sub-plinian
eruptions (order of +*1 m- to +*0 m- ). Hence, the most important process in generating agglutinates is rapid
accumulation of voluminous tephra around the crater which are generated during sub-plinian eruptions.
Key words : Ohachi volcano, Kirishima volcano group, eruptive history, sub-plinian eruption, agglutinate

0123

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DIA Consultant Co., Ltd., Sabo and Disaster Prevention Center, ,῍,1,῍- Yoshino-cho, Kita-ku, Saitama--+῍20-2, Japan.
N2+.῍*+2* hiQj8Skl 2῍+3῍+himnn:opqrnr
Department of Earth System Science, Faculty of Science, Fukuoka University, 2῍+3῍+ Nanakuma, Jonan-ku,

Fukuoka 2+.῍*+2*, Japan.
N23*῍**0/ #$%Qst +-,+--/#$%mnn:opu*rnr
Department of Earth and Environmental Sciences, Faculty of Science, Kagoshima University, +῍,+῍-/ Korimoto, Kagoshima 23*῍**0/, Japan.

 

Corresponding author : Masaaki Tsutsui
e-mail : m.tsutsui@diaconsult.co.jp

A_*h8 h*"FG2

Fig. +. Map showing the location and topography of the southern part of Kirishima volcano group. Contour
interval is +** meters.
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Table +.





3Comparison of tephra layers with previous studies.

 

  !"#$%&'ABCwxyz Fig. -ABC2xyz/t1( )*+,-. /01 Inoue (+33-)  { 5'& AsT KT

2/31 (  04 5'& 6, YABC |Oh+ uv Oh,} /RS%&'

7/89&'%+% Oh+ uv Oh,  ~ % Y(, : /;< /+sL),#~

!1 ( +

=41 ( ,>/? % 

* ~

2@  ABC DEF+*

(1,-** cal BP) QJ , 

0> G'&HI1

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% .,1**ῌ,,,** cal BP $w/% %+% ~
G'& JKABC

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L MNO,ῌ+

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L^ABC ^L )¡¢% ~, 

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(+*~

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% KTU.VWABCY (AsT) ABCY (KzT)

$w G'&? '[' (U¬ABC\_ABCY (MsT) abABCY (ThT) acfbT  mn/­%& AsT )%&'

-* X

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ABCY +h++(TgT-+hTgT-++)ij (k* +/ Y

ABC XkZkl^mn U9&o
k

(

,Ppk

Table +

BCP  DEF/t1

qr

5s

 Fig. ,a uv ,bA%°[s TgT-++ T  *®1 ¯+/ 1%°[s "²¬ e¯+ῌ± ,³´ |Sm-KP µ- +1+0h+1+1 $ ;¶·¸¹. +33+} ):º#%&'(Figs.

,a, ,b) p*  Sm-KP T  » + m /¼14



Fig. ,a. Stratigraphic columns showing the lateral correlations of representative tephra (Locality number +-+/).
AsT : Araso tephra, KzT : Katazoe tephra, MsT : Miyasugi tephra, ThT : Takaharu tephra, TgT-+TgT-++ :Takachihogawara tephra +-++, MiP : pumice of Miike and Sm-KP : Shinmoedake-Kyoho pumice (AD +1+0-+1+1).

Fig. ,b. Stratigraphic columns showing the lateral correlations of representative tephra (Locality number +0-,+).
ThT : Takaharu tephra, TgT-+TgT-++ : Takachihogawara tephra +-++, Sm-KP : Shinmoedake-Kyoho pumice(AD +1+0-+1+1). Locality number are referred to Fig. ,a.

*»+¼

5

Fig. .. Isopleth map of Araso tephra (AsT). Values
in centimeters. Dashed lines indicate the limit of
distribution of tephra, and dotted lines indicate theisopleth.

hxy$%&/vz,ῌ+ῌ, ῕῔ῌ῍῎ΐ (KzT). |}{$%&5 (KzT)  68'~9

(Ybcde5 (KzS) / 68'
~9(kF5 (KzA) #6768'<=

>

/o'

(Fig. /)

9#>Y KzS  Fig. ,a ^ / 5L
 +3 cm  PD 'pqYZpqlDm
Fbcde fgP *./ cmi CDbcde
Fig. -. Idealized columnar section of tephra layers
from Ohachi volcano (not to scale).

fgP *./ cmi hom#CD  lDbcde5
fgP + cmi ' -z o=

AYoE59-> '



9->#= y'  , km 

. - 'pz ./}

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$%&'(  )*+

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Z' 5L - cm F5/T

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23$%&5 (AsT)  6789:;'<¡¢F k£FD£lD!

 4

=

>  ?/@A BCD EFG:'

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'ST

(Fig. .) 7UV'WX' KzT YZ' ,/ cm CD EF9[\]

Fig. ,a ^ +  5L + cm CD_`aD

bcde5 fgP *./"¤ mF#

5L#  lD$¥G:¦§X#¨`©D9ª «%&¬
KzS / KzA '$¥Gw>/q

Inoue (+33-) st­® (+331)  KzA 9¯'.$%&/°±. (=(z$¥G KzA #= .²³´T/ KzAkZ)qµ@¶´Ok$¥G/}

cm hP ../ cmi  4jbcdekZ

4 ·} KzS / KzA  'p $%&/

'lDmF9n /ov.

AsT pqYZ' rst

R/v" $%&w#'u
.T AsT ,ῌ+ῌ- ῏ῒῌ῍῎ΐ (MsT)´>º¸¹$%&5 (MsT)  mF (MsA) µ¶·¸¹ º¸»¼

6

Fig. /. Isopach maps of KzS (scoria) and KzA (ash)of Katazoe tephra (KzT). Values in centimeters.
Dashed lines indicate the limit of distribution oftephra, and dotted lines indicate the isopach.

Fig. 0. Isopach maps of MsA (ash) and MsS (scoria)
of Miyasugi tephra (MsT). Values in centimeters.
Dashed lines indicate the limit of distribution oftephra, and dotted lines indicate the isopach.

 

5 +- (MsS)

MsA

  (Fig. 0)
MsS  MsA

 q\r\ ,, cm / cm mn .. cm 6

ThT-a

 

 !#$ WXY9 + cmZ %&'( 987 ;V3u&-!"#$%&'( $) * +,-*.

Svwxy <0 p ThT-b/ 0123 Fig. ,a 45 1

!  WXY9 - cmZ %&' 9 +*6 +0 cm

 789: ;<%'=>? @2cm

2A2AB4 6CD23 EF GH

vwxyR~" EF }

IJKLMNO_8/^_ tF

MsS $)%&PQRPQ ' , S0

1TUV30123 Fig. ,a 45 1

6  !  WXY9 + cmZ 8

1 cm,ῌ+ῌ. ῐ῏ῌ῍῎ῑ (ThT)F%



ghij= (ThT)N{ }kI^  ThT-c  R} 988p

cmZ'( czc OR
ThT-a R ThT-b ThT-b R ThT-c  2A2A$`abc ! de8 t J'E

 987:l;( ThT-a ThT-b mn ThT-cc{|nF z !  WXY9 +./S[\F;]' %&'( E\ I^_8$`abc ! defNO

@t# z;(k- o0 p q\r

t ' q\ ¡ ThT-aThT-c¤$¥\$)%&s mnsPQ 01TUV301

FR«¡&\ '¬ ThTt (Fig. 1) ThT-a ThT-b mn ThT-c¯

 Fig. ,a 4 ¢£¦23 §2F - ¨¤$ ;V3©ªu\­®ij=( $° CDK±V3 W,ῌ,ῌ0 ²³´Z¸¹º»T¼

7=7' >/ TgT-/TgT-1  ?@AB C A
DEF< G(?' H TgT-3TgT-++ BI 
12JKDEF< G(? 45/D LF<=/'
TgT-+ MNOMPO QR?S T

N3 UVWIVXY

/0?

' Fig. ,a $% , E -0 cm ' MsA
I  Z([\Q]/ ^ _`Oa
bcde f$E gh/0?' () TgT-+ 
TgT-, iOjTNkU l cm mn

Z(MNOop?qrsOTNtuv7
w3 jTNkxyzA{B12
(Q|/0?w=}/0?'TgT-, ~ Q?iOPO

~ TN OQ?
~ B @d'   , -  ' Fig. ,a $% , E
 / cm # L *./ cm& ' ThT-aThT-c I - 0xyzAB AA

o L/  ((?Jn ¡'TgT-- ¢OqrsOTN3 TNOQ?~ POo`OQR?S TN (' Fig. ,a $% ,E +, cm ' TgT-+ I  UVWIVXY12 /0?' () TgT-- U £ t?iOjTNkuw'TgT-.  n3¤k¥TN ~ S

TN - ¦" #TgT-.a TgT-.b ,- TgT-.c&'-  §¨=7©ª( m4{«¬A' TgT-.a TgT-.b,- TgT-.c  Fig. ,a $% +/  AA *./ cm
+- cm ,- . cm E' TgT-.a p­O¤k¥

TN POo`O QR?S 
Fig. 1. Isopach maps of ThT-a, ThT-b and ThT-c of
Takaharu tephra (ThT). Values in centimeters.
Dashed lines indicate the limit of distribution oftephra, and dotted lines indicate the isopach.

TN iOQ/~ (+d' UVWIVXY12 /0?' T
E4® , cm ¯ °Y±?'
TgT-.b  iOPOQ?~ #

L *./ cm& o;A²(~ (3,ῌ+ῌ/ ῒΐ῕ῐῑ῍῎῏῔ +ῌ++ (TgT-+ῌTgT-++)

HA`O³´d'  e7' TgT-.c  MµOMNO QR    +++ (TgT-+TgT-++)  ThT

 Sm-KP 
TgT-,  



?S TN (3 UVWIVXY1+* !" #Fig. ,b $% +1&' (2 /0?' H MsA o TgT-+ /g) *+ KzT MsT ,- ThT ./012

h¶· #[\Q] abcd& /0?'3 45/06789 

TgT-/ TgT-0 ,- TgT-1  ?@AB Q

 (TgT) :;' Fig. 2  TgT-+TgT-++  <

R?S TN (' 4®E +, cm B/ 8



Fig. 2. Isopach maps of TgT-+, TgT-,, TgT--, TgT-.a, TgT-.b, TgT-.c and TgT-2, and isopleth map of tephra
layers from TgT-3TgT-++of Takachihogawara tephra (TgT). Values in centimeters. Dashed lines indicate
the limit of distribution of tephra, and dotted lines indicate the isopach or isopleth.

º¤¥ »¼



  !"#$%& 'TgT-2 %()*+,-* - ./ 01*

 . R /| (KjL) |gE  #  ¡' g %RS& I¢VE£ia|  ¤¥I¢| (CrL)  ¡'  F¦§¨©% ThT ª 5«g¤¥?@AB

J#KLJM§¨© eOhSf ; ¬­® +322f .' Table , ¯°=* 56 > ?@ABC9DE&' Fig. ,aH / cm ./ I(SnL) | (JdL) | (TgL) 

23* ῌ456 7 89--:;<G , %

9/

±²x"| ³´µ¶ n Fig. 3 ¤¥NOPQRS '
TgT-3 TgT-+* TU TgT-++ %

VWῌ456

|¦§¨© RS·¸¹

µ¶7 89-2E&'  

2

%

!"#$

VWXY -%&

TgT-++

Comparison of lava ﬂows with previous studies.

Z[ & \]^_`ab%cd. eFig. ,b
TgT-2  Sm-KP

Table ,.

' TgT-3+TgT-++hija

FG +1f' b g
kl TgT-3+

9mng' TgT-3+TgT-++ %

op22qrs/tguI Jov
wRS ' &x IyEzvH +./ km

FG%{m +* cm  |}W',ῌ, ΐ῎῔ῌ῍῏῔ῑῐῒ~% RSa||W

Fig. 3. Distribution of lava ﬂows and pyroclastlc ﬂow deposit from Ohachi volcano. Their stratigraphic positions
are also shown in the idealized tephra section. Base map is + : /*,***-scale topographic map of “Kirishimayama”
published by the Geographical Survey Institute of Japan.

¸¹oº& »ok¼'

10



b-! c -./IJ. >?@/

 (+322)    -   ῌ῍ 

!

" 



* +,!-. /01

! 23ῌ῍ #$%&'()dῌ῍/eP38

8fg /3-0+ wtῌhij ab-!
e= kl (+3,,) mnop (+3/1) nok(,**+)

qrQ$ stquv

qwQ xy +/ῌ῍45! Oh+ 67 Oh, 8,/,*** HzQ { xy +/+*,*** +32/|,῍+ 9 3:; #$<"=-. >?@Htq}~Q { xy +/-*,*** +333| 67

AB!C/D="/EF3

- 5 qw"=

Fig. +* /G H -./IJ.

%&'()LK

MNO=P3 K, O-SiO, Q SiO, wtῌR /!/

K STUAsT D /*-/+ wtῌ/S8VW  SnL SIU
TgT-3TgT-++ 67 CrL D /2-0* wtῌ /$$XW

G

H



^ qw:F!/ Fig.++ ῌ῍-."= 3/:;

E E -. -."qwD5  -. C= /qwFK 3DX -.
!/D ]P^_

:FP!3geP 

K ` /+-/0 wtῌ

aῌ῍



 23 ThT-b - YZ[\ 0, wtῌ/S8XW!D stquv qwQ xy +/,/,*** E "= ]P¡P ¢£Dqwi¤ !C/D¥¦P! ]P§ῌ῍ -. / 3,ῌ,ῌ+ ῐ῏῎῍ῑῌ (KjL) (KjL) *+,

 S8¨AH©"= 0 km ª P3

G2A ! «¬ / m ^/ KjL *­Z&H®t¯

MsT P° KzT

H

! X±!" * ²# 3
Fig. +*.

Whole-rock K, O-SiO, diagram.

;/
"=* * ! r"³=³\f$%´µ\¶·Fig. ++. Schematic diagrams showing geomorphic development of volcanic ediﬁces around Ohachi volcano. Eb :Eboshidake, Yn : Yunotanidake, Ss : Shishikodake, Yd : Yatake, Ry : Ryuodake, On : Onamiike, Ot : Ohatayama,
Oh : Ohachi, Nk : Nakadake, Tk : Takachihonomine, OTk : Old-Takachiho, Sm : Shinmoedake, Ft : Futagoishi.

tu $¼


ShTU _VFz

,ῌ,ῌ,  (SnL) (SnL)+.2* ; W +300b        /./ km! " #$%&'( % )
*+,-'(,(. /0
3/* m 1 234 56 7

8 / m 9& 2 +* m 9&:. ;< '(=>,*,/ m'( SnL?(' MsA

K, O wtῌ

CrL '( .]'(MNO DX

CrL

YH(F Q ddZ
 (OhSf),ῌ,ῌ0qFGH (OhSf)

// "' 6 (4"2A0
0 +,+**+,*/* m 1%oCp

[[ cm \q]Qw,. zzM, _TM^_EF" SnL  MsS

MsA  D%

 G.H,,( !&,IJK '(. MsSMsA 
MsS $

LM6N SnL)OP*+.0( Q ,R

, mb `O]8a{ bc _TM^ . m 12b c d / 
6 OhSfN"M,eQHQ.f C

" OhSf

/ ThT-b "(

ThT-cLM6



ThT-c $ )OFGHghB"

,ῌ,ῌ-  (JdL)

S. (JdL)
U0

SiO, wtῌ/3.1-!"3"'( @# SnL

A MsA 7B SnL $5C

D%C11

/ OhSf

/   T2 ../ km 12%&'( 7/m 9&3( 045VW/ X(,!

68 Y7, JdL 8Z (OhSf) .9[:\ThT-c $B4"]'( OhSf?^ _,-,-0 =`ab JdL)(;<'

ThT $ )OA/ <UB"vX]' (i  6 djvkl& & 8 / m 9A7{. mn 3FG
'(N2 T2U0e_ +./km o 0 10* m 1%&'(0/ OhSf
'p¡&(i% 

 8 ,- m 12

(F Q R-c>,dd7{ '  r2d+,! x]' ¢,2 ,- {,ῌ,ῌ.  (TgL)

045VW (TgL)£¤v¥¦w.§sB" / OhSf

<?%]/e

& T2U0 ,./ km 12%&'( 7 8 , m 9& e1+ m 9&B 3( TgL

/

?('fg@hi:\' TgT-( N"9j/A/"3"'

ekF'l". %&m4A/ @%%Bn TgL .oCp A/Bn TgL
7B. /+* m 12 ThT "( TgT-, qrstuvwx]'=`ab .]'!8"3"'( _.῍+῍,
TgL

TgT-, $ )O(F Q R-c>,dd (CrL)D (CrL)

_ +./ km o%Jq&__ - kmbe

6. @"9U?('2 tuS0 JdL A oM

'( (Fig. 3) % 045VW/ X(68 Y7, JdL 8 OhSf .9[:\B4 !
"]'( NxO,¨©uMN

ªV _*v +320ab ]w%:x'( JdL A

OhSf .FG OhSf .«¤h x^&

G ¬yB"N-­62",(,? / z6%A/

T

00 +,+0* m 1% OhSf ]Qq^ ,m6M,® bc.

oM'( (Fig. 3) NFGH w¯ °±&²£³xO. eQHQ,ῌ,ῌ/e_ , km %Jq

Z'?4´µ¶w·v¸v2C",( %%T2Y

 ¹{&,r|hC",(. ?

 D/ yz^{(' 6 |]'7}

  OhSf

EFGH "3"# }". D/NFGH%~(A.] OhSf Oº/ I J,~K<.oCp A »^B"FGHEF"e1LA/(MNOP.M'(. _Q R ,**/b @

Jq6 N¶·¸&¹º' »¹£(¼)

12

Fig. +,. Sketches of the crater wall of Ohachi volcano. Ed-L (Lower unit), Ed-M (Middle unit) and Ed-U
(Upper unit). Ed-M is subdivided into four units ; from the bottom, Ed-M+ to Ed-M..

- 

 I8 Ed-M+REd-M.
Ed-M+REd-M.  

    ! "# $ %&'

()*

+

,- .# /0 12#  345 67 89:; 2#

 IBC + 3Rl3KLgh,i - l3gh,ik- N 2 z{;<=2$9:%:# +

# -

 , 3, &l32

B<=>?@ABC D E8F>GH 89

C(3gh,i # $2 :I; (Ed-L) J; (Ed-M) KLM; (Ed-U)- UQ

:

- N 2 (Fig. +,)#

# / + BC - ¡  1(

 (Ed-L)-ῌ+I; (Ed-L) ¢;5

OPQ " +/R,* m STi-;£>¤¥¦R§§¤¥¦ BC

i- Fgh;U V WI XYZ[ >\ ]^_2,i;§§ ¡(!¨k

># `abH

E:#cdefgh,i;2j1k l3m:#. &' ()*1noP+,-2  Ed-L &' np%F# /C/(BC2

WI Ed-M+©/( ;U +/R,* m ST2 oP2ªf U +*R+/ m STi-(>9:# f`abHc W«;U +/R,* m

2> 1I  q: Ed-L 2:6 , m ¬M d$:# Ed-M,

rst&# >u WM  k vwxy

ST2 "P2 Iªf i-(

Ed-M (>9:# WMz{2%:#-ῌ,   (Ed-M)

J; (Ed-M)
|P}:~ 

;U -* cm ST­3®¯;

 °#$±2 # Ed-M

Z[ 1>#  k Ui

2  

;U +*R+/ m ST

Ed-M, (²:# "P2  M(I , ;³ªfi-(>9:-(>9: OP q:fg

# /WM´%2

h,i;2  k> . V

 Ed-M.

­3®¯de# WM

 ;U / m ST(µ q:f2¸¹ºY¶» 



13

 P)v<RS-ῌ-  (Ed-U)

 Ed-M /0

1 23N ) Ed-M  Ed-U  

 (Ed-U 

,!

JD'b (TgL ; Fig.+,) mne" # $  Ed-U  $%&'() *+ +/,* m ,-). Ed-M /01. 

234 56"789:;
Ed-U =>?

.<.ῌ+  @A1BCDEF).G<<H IJ



 Ed-U  T

Ed-U  T&'(KLMNOPQ <RS

UVWXYZ[\Y] ^_`a bc d

 


KLM Ed-L Ed-M [\$VDb
#<¦S¡¢U£¤#<# ¥ ¦ Y§c¨KLM (KzT) 7©KLM
<# 

ª

N ¬

eWXYZ[\Y]f =>3 gU

(ThT) [\7 8 9 « © KLM (TgT)^_`a - h(Fig. +-) D4 ®¯Ym|{$ Ed-L Ed-M [ijklYZmno34

 . pqrst u)v

­@Q\ Ed-U °±m²3 ±m³H

wx  Ed-U  Ed-M+Ed-M. yz{ Ed-M # ´|}m~ppqrst) + ,. m ,-.ῌ+ῌ+  (Ed-M)). 5 +- m Na

Ed-M  Ed-M+Ed-M.

tDG

4 ).ND DY. uQ  µ ±D^_`a¶ VG@A1·? F{Q <Fig. +-. Correlation of the proximal to distal tephra layers of Ohachi volcano. Ed-L (Lower unit) corresponds
to KzT, Ed-M (Middle unit) to ThT, and Ed-U (Upper unit) to TgT, respectively. Ed-M+ to Ed-M. correspondto ThT-a to ThT-d.

p­qº»r ¼º7fst

14  Ed-M,

 



     


ThT



  ThT-b

! ThT-b"#$ Ed-M, %^!0  345D8<:(/.g7; k!
.ῌ, 
Fig. +.  34G xyz-. e{ :H  | : U}~bf  

&"'%() * +, ef NOH" ef  SiO, wtῌ" .῍+ >8-.

.3_`abIJ 0' MsS % SnL B

/0

1 Ed-M +Ed-M- % Ed-M. ThT-a  2

1 Ed-M.

 / m %

 345

&3_`abKL @  

678 3459$2M%34G  _`abIHK

-   -0!:! .; Ed-M-

HNO B HK 

ThT-c 8< :=3459$HP%1KL()QR8< %m

Ed-M.

 ThT 3>8<.%)( ThT-a?ThT-c 1.

; ThS-d %@AKL"S?0!
T2  AsT () MsT ( SiO,

U-0! (/*/2 wtῌ) ].

.ῌ+ῌ,  Ed-U).῍+῍+ '-.B Ed-M  C<DE Ed-U

 %-0 ThT  TgT-+?TgT-++ !F<ῌVJx  (/-0* wtῌ) .G ThT

3



2

W

ThT-a ()

ThT-d (0 SiO, wtῌ U-0! (/,// wtῌ)

(8<%:? ! Ed-U

 TgT-+ () TgT-3?TgT-++ (0 1n SiO, wt

 Ed-M 1-0! 

! CG7 :H" (TgL) "IJ 
TgL " # $ %   1 K L ( )  ?

!  Ed-U

TgT-,  <)X  Y3Z W3u"IhZ"[&0 SiO, 8!()VJ%"\-0!%"'(-<:!

&! Ed-U  1'(3MNO3)

.ῌ- P* +,-   TgT-+ %Y  PV NOBt:(-Q%() TgT-+   .1RSTUI/0V3M
-* cm W1

X 1Y?Z[\%!2: - ^ ¡-  ] +  ¡)¢?£RSTU ¤ A¥"d/0 i2¦

C%-0+^ 

3() TgT-.a   .; 1RSe f %(;() Walker (+31-) B§¡T`

TgT-.b  ]. TgT-.a 1RST

t3-  KzS MsS ThT TgT-, NO TgT-

TUU  Y?Z[\ , 4!3MB/0 -.b^_`abc8< C1%  - ^F<§¡T`t3_/0"m-0!

_`ab"d^%!() TgT-,  
1'(3MNO3)  TgT-/?TgT-++ !

@ :=  H"  !

] ,  ¡ ¤`M?£ab+c¨!
'(3M():X A¥"d.F Y".

F<( e- 56f g7 .h-©no

1 TgT-+ %i-P*8- #j -?/ cmf +320bf u +3.3 dW¬ghi3 e­j +33+fWi2

Z >8<0!7 :®:H9":#J() TgT-3?

TgT-++ 8<g7; k!
.ῌ+ῌ-  Ed-L)
Ed-L©ªv +3// dW«e e7% B ¯~°±t3²kBX>8<. MsA TgT-+ TgT-- NO TgT-/

34<l:% ,* m   Ed-L

@

] -  ¡  /0V3M"¤%³´µ %-0  AsT KzS NO MsS  -3B Wl% : !

^-(:! AsT : KzS : MsS m= no , : .2 : 1

F<m¶-. , ^e.῍/ >pqf X 34?9= m= l:% MsS TgT-. TgT-/ NO TgT-2  

@%rA<s Ed-L:= AsT NO MsSKzS 8< TgT-, NO TgT-.b %3B

+^

 

¡·}·3_/0!

 i2



: KzS u ThT:  ³´µ3¸n +^ :!.; !

t m=uvw -Q-0! C>2D8<:X·}·3 +o-.( +o-0!.%-06

u!EF:C>-. TgT-, NO TgT-.b /

7  %-0 D8<(/.

0 345 / m W-(: AsT % MsS ¹º»lmR¼]R`

15Fig. +.. Variation of Whole-rock SiO, content of the erupted material on the crater wall of Ohachi volcano anddistal area. Br : breccia. Date of CrL are taken from Shinno (+300).

.ῌ. ΐ῏῍ῒῑ   +33, ; }~ +322 ;  +321 ;  (+32/)   +.C

+32/ 7'( MM ThT Z* 3+*   +331 ;  +33, ;  !"#$

 M  +330 ; ῌ +331' )

%& +332 ; Okuno et al. +332'( )*+ ,῕-.

+o 52( wx Okuno et al. (+332)/012 +.C34ῒ

9  : ; <+.

/ Table - +56( 78 ῒ=ῒC>&%#?@<+w2f7 +.C[\/M ]Rb῔b/dῐM21 KzT ]RINTCAL32 (Stuiver et al., +332) +ABCD$EF&

1'

OP (+331) < lmrr+6ῌQ ,῕,**+) /L῍M2( N2 OP (+331) < ῌQ῎BRS KjL B JdL + ' +oW῏X!YZ/[\M/^\M

2( )*[\_.+ΐ`a ]Rb῔cdef
7gh/ijk lm]R
.ῌ.ῌ+/dn6(

( ThT +o< pO (+3/1)
1tuv

b῔+q*M rῒ 122 s ῒ 1'

ῒ P'

B^\M2(KzT B ThT +¡¢)B/5

M2( ,῕£*2 KjL ¤¥!¦§¨ +.C(Table -) A Okuno et al.(+332) ©ªyzB«¬f

AsTῌ KzT ῐ῎ ThTKzT 34 ThT +o<  +. C

KjL B JdL / +,-/ / 122 sῒ

%GHIJK Oxcal ver. -.+* (Bronk Ramsey, +33/ ;῎TUVW῏X!YZ/[\M ]R

 ThT ]R

tuv


]R

]RB^\M w

xyz-.A)d1/{|M2  +33. ;i( )*)B* KzT B ThT ]R<­ ®¯°+ rῒ 122 sῒ 1'34+,-/  ῒP'

B±²Mῑi³(´Z AsT <£*72µ KzTMsT 34 ThT ¶·¸¹/AB+ ·¸T*¸¹+º6 »º¼,-.

16
Table -.



Radiocarbon dates for the erupted material of Ohachi volcano.

  AsT

?SE

ghijklhi MsT C-O? 3 89m

KzT  /*,**   

no"S4 5 0^_`pAqrs]\ +332 ; !  AsT "#abctuvwx ,**-1 MsT /yz:{KzT  +** $%&'( 1** ) *+.ῌ.ῌ, ( 30* #)| } 0~1 {
+5

/

 ( +++, 0 -1  ++01 0 ,1 

MsT

MsT  ,-./ KzT 0122 1

++2-

+5

ThT 0+,-/ 1 /0 ,1 { EG' | }{

234 5 6 (,**,)  Okuno et al. (+332)  +.C

 ~/:7+  /> 5> 

# 7 / MsT+* 89:< (+331)  MsT

=/ " 2**+*** )





 ;

SnL />5  (



:

"

 ~

5DS4
G55L 3eC #

 3  ( +++, 0 -1 /   0  MsT @A ( +***+,**  SnL BC  !¡1 ++01 0 ,1 /( ¢ ¡ 0^_`a@A ( 2**+*** # D

 EFGbc£¤"1 ¥¦{S4 5§47:¨O? // MsT /H%# IJK?>L

=/

M

  ?4

C  % O =/&

55 (Table -) E4 .ῌ- ND

+.

FG



S5 G 0 km #©/-ª% (Fig. +) E O? «.¬$­L:® E  ¯L®  5§47

/ MsT  OP QRS4 TUV:!°% {7±&²'³7

E( 5 &´  !:{µS4 55z

HW%XG

O

eX&?

 *YZ.[\] ^_`abcdbf

²7 E ¶ ·) MsT :#

./¼t#$% $h
Table ..

The estimated eruption age of Takachihogawara tephra (TgT-+ to TgT-++).



 3**++** +***  
.ῌ.ῌ-.ῌ/ 

t# uvL .wUVW %v $xy
$x$KL]^%z$ . {<  | -w

TgT-+TgT-++

TgT-+TgT-++   ThT +,-/   Sm-KP
+1+0+1+1   !  "

M&}~: ' (UVW!+,+,- -./01 $' 23$/45617 ,* /8!

:;4 <4< =>?@A$'45GH)

F

BC<!


93)

5 TgT-+TgT-++
3 .ῌ0 DE$AIJKL<: '(CAUVW (TgT-.

a)  u* *./+* m- 2b: :~ '
0



(

CAUVW (TgT-/TgT-1 TgT-3

TgT-++)  u* *+ *./+*0 m- H<: %v!g !

+

KzT  ThT  $%,UVW45GH) -$-ST)

UVW KL<! 45 $% ./%AM1NO<!  : TgT-+TgT-++ PCA $ 2QR<!ST) :UVW23 XYUVWZ[H< 5

7 TgT-, ]^ TgL $Z-_ Z\$) 5 Fierstein and Nathenson (+33,) u[#$%&' () !   * 
 +//. 

17: +. C Z\ +-/* GH`<!

B +/+*,*** +32/  ,/ m 8[v) ,/m 0

b!T)!

%<!}~: $x$KL%z$g ! 12
L3[!u<:772

: :~ DRE (dense rock equivalent) v

3 aZ[H 4b:  cL[}~ Table / ~: 44 $%def TgT-+TgT-++  $Zg ! 

[ +./ g/cm-

h'iUVW]^jk[< Table . 
TgT-+ mn C Z\ (10*o3* BP ;+.

Okuno et al, +332) pq45

 TgT-, +.

 +,/*+-/* C Z\ (/-*o.* BP) ]^="TgL  +.C Z\ (/,*o.* BP) 45 +-/* G

H<: 
)!

$xy[ +., g/cm-

$x$KL[%z$[ ,./ g/cm- 

H<: UVW $x$[¤¥ 5 +.,+*2 m- $x

MGH<:;l+.* g/cm-¡¢£[ *.2 g/cm-

y5 *.3+*2 m- %z$5 *./+*2 m- 3 ¦u*5 ,./+*2 m-  ;l¦ u* 2 § UVW<! u<:
.ῌ0 

 5 $N $'#  TgT-- +.

C Z\ (03*o.* BP) $)=>6¨[ ©ª¢«¬$[­v<:& (AsTKzTThT) 45 ?@Apq45  +-/*+0/*  TgT-.  p[BC<gg ®¯°±$[­v<:&

q45 +.C Z\ (,,*o.* BP) [r <  +0/* (TgT-+TgT-++) ²³´<!

 : TgT-+ 45

GH<: TgT-/TgT-++  $Z

TgT-1

TgT-++ 4!7 7µ[ST

TgT-2 ]^ TgT-3 g ! +.C Z\[:*!®¯°± $ (TgT-+ TgT--) ¶CA©ª¢«¬"s\723 pq45P42
 +0/*+1** GH<: $ (TgT-, TgT-.)
/ -.

:

·¸

 TgT-®¯°± $7¹8º9$%¶z;4»;

$ TgT-/TgT-1 ¶YTZ»: ¼Z ;<=18
Table /.

Volume (DRE) of erupted material of each eruption of Ohachi volcano. Eruption age is also shown.

TgT-3TgT-++  4 3 >H65zj5]    1**z*e+,  -.7M #  ! "# %&'(#

+,-**

$

,.*)+* m /ky  (Fig. +/) *
2

 + , 

-+*1 +*0 m- -./. (KzTX Vh@, / > #z*#qr/Fc *0 !pVhe,  KzS #\M^ +/* mVhThT) *0 +*0+*/ m- -./. (TgT-+TgT-.) +*/A 0145}7* L@ ThT

m- -./. (TgT-/TgT-++) 123

*0^ 2* m

45

678 AsT *0 ThT "#9:*0;</.*$ = 3 >?@ ABCD 2 >  E
 3 >?@ F TgT-+ ?GHIJK 

A

11*

$

*..)+*2 m-/ky HLVh A  TgT^_,F O2b#PFgz{ ,* m # 45
FP4 z*36 -S+ 
.

 KzS  ThT # }M0 , ¡..*)+*2 m-/ky O4 +/+* P45

 P4!p¢£4¤Vhb\MF5

 Q RSTU F V] ¥¦6 E§¨©ª«qr¬­®

M?N A#BCD W#X5 AYZ[ ,**/ F

BCD  5¯MH #Vhi H°#P4 L \0

F~ z±5"}#X¯ Vh@1

455]

.ῌ1 ῍῏ῌ῎ῐ6¢²³7455^_`.a bc 

SX.#  z±5I

Fig. +0 d6 !

efM45^_g

BCD´ 8,xµ¶©·¸.¹!

Vhi Vk"l m#$V An +/F µ¶©·¸.¹bF ThT-a ThT-b ThT-c+*,*** +32/o H !p! ]45^_  +*1+*0 m- -./.# º µ¶©

%gqr&gVhi st u0*vw#·¸.¹b455 MsS qr TgT-.b '^wxr(yF ^  gz{#

 +*/ m- -./.# Q TgT-, H +*/ m- -.

z)*0

j54

,/* m

# z)

-* m e^_Vhi |p45 }F~ Vh^/.*I z{g#9x#

 z{&g#µ¶©·¸.¹P45 TgT-01;<4;

19

Fig. +/. Cumulative magma volume (DRE) versus calibrated age of each eruption of Ohachi volcano. Light :tepura, upper middle : volcanic ediﬁce, lower middle : lava and left : total erupted material.

Fig.+0.
, 

Cross section of the Ohachi volcano.

 (TgL) op45qrst (Fig. +1) uX/( .bc

 !"#$%&'( )*d v"@mg ThT-c /MwxMOy TgL+$ ; Bacon +32-,- ./( 01%%VWLbcdz{|}L~"N- .

+*0 m- 23X

456789:4; <=>?@ABCD

/("cdE(F%GH"IJKLMNE-< ,**., #$/( 4;m5"O PQ3 (+322)"wxm?dACxE;%LL+,+** m ^_ %`aXEbcd

\x }XE}L;q eNM ;Y[\5LfghLN )01/MCxE.m%dACxE- KzS

ῌ ; TgL ij, klmnF- L[L01;Y

4;%gRS< KjL 5LMOy .4;

E

;YZ[\]

01RS<=TUVWX ;< )Bt $»¼T ¨»<©ª20

 TgT-+ @U3 11* Z&<];)
 +/+*

^.=

>*_?, 

Sm-KP `+1+0E+1+1 A @U 234a@0)<];
-A   KzSF, , b

ThT  , bc&AdB];)(G`+*1E+*0 m- eJfJA 

HIJ

"

234

 % g*! 0*"C, \234,& KLMN"234 5h)*O`+*/ m- eJfJA

CD<];)(GHIJ

D 1)1

1,&i*Rc11@jc 8Ek
"C  lF,)

Fig. +1. Distribution of tephra and lava deposits
around Ohachi crater.

.A ']; ThT  ThT-a ThT-b CD ThT-c 2234

./!

% g* 9QgmXLnoJp
", mXLnoJp ".qr!j 8Ek"C GH)IY?,      ThT     !"# $ %ῑῐ

JKLsMsNtOPuQ vwRxmyz{

&  '& # 

STUVQ vwRf|}~LpW6X()* JdL & +,-. * ThT-c 

Q YZsYZmm J[ Q/& '& # 0)(\]^\_`: aSbQ c[
vwRdLeQ   f,g0<

)1

 
/ῌ ῎ ῍ ῏234 5678 :,; <  9

234!=671"# :,; 9>? @+ $1 )
+A 
KzT

-,

MsT

N

 (GHIJ

 )*O

,-1

tuwῌv wQ JKLxyz(¡JY {Q ¢s67 6!|£,< j#l¤¥~n¦`§¨_: a©ª«Q ¬ !­Bl)i¤£g0< JKL
sMs ® Maria Hannah Mirabueno Q 

JdL CD TgL

zH ,g0< \]^¯

0 P1! CrL  / :&'F 5

E °±a ²)³,

9Q KjL  KzS

KLM

+# & 5./! KjL JKLnopqs"WrQ sg0<  fh}g|£ [f234 +B". AsTThT CD TgT-+ETgT-++  +/ %&'F 

[ Q N h5(si".j,g0 .jk :,l)mg0<

TgL  TgT-, 

SnL

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2  !)RS

./g0< 8+XQ ´QCD µ¶ Q ­B)¤£g0 [!5 !T,(GHIJ

+,

3 +,-** 4 AsT ",56

@8E² 1¸<! )- [f,

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,A,@U 3 ,./V+*2 m- WXW 7

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f00*·F<¤¥fz 9/|£¹& zN^®s ¦ `0,/.*/22 CD *.0.*1+*A º§<[>&Uῌ ῏ ῎ ῍
Bacon, C. R. (+32-) Eruptive history of Mount Mazama
and Crater Lake Caldera, Cascade Range, U.S.A J.
Volcanol. Geotherm. Res., +2, /1ῌ++/
Bronk Ramsey C. (+33/) Radiocarbon calibration andanalysis of stratigraphy : The OxCal program Radiocarbon, -1, .,/ῌ.-*
Bronk Ramsey C. (,**+) Development of the radiocarbon
program OxCal Radiocarbon, .-, -//ῌ-0-
(+303)  
      +-ῌ-*
Fierstein, J. and Nathenson, M. (+33,) Another look at thecalculation of fallout tephra volumes Bull. Volcanol.,/., +/0ῌ+01  (+330)  !"#$%&'()
*+% ,-./"012  (῍) .2ῌ/3
34 (+3.2)  56!0789 :;<=> +-, ,/+ῌ,/3
? !@ (+33+) "#$%AB ,** C&'()%D&E*F+,G% 
0H 31, 20/ῌ202
Imura, R. (+33,) Eruptive history of Kirishima volcano
during the past ,,,*** years Geogr. Rep. Tokyo Metropol.
Univ., ,1, 1-ῌ23
? !@ (+33.) 0 - .  03, +23-,*3
? !@/0 (+33+) I12JAB -**C&E*  -0, +-/ῌ+.2
? !@/0 (,**+) 03 / 4 +03 ++ 0 K
? !@,L5M (+33,) NO6PQ7
+.
C 8  -1 33ῌ+*,
?RS9 (+322) IT:;<&E*U V 2-, ,0ῌ.+
Inoue, K. (+33-) Across-arc minerelogical and variations
in Kirishima Volcano Group and its implication in thegenesis of the volcanism of the Ryukyu arc (ῌ) Sci.
Hiroshima Univ., C., 3, 1-/ῌ132
/0 (+313) NW=XQYZ  ,., +20/0 (+32.) [>Q\ ]?^@AB_ AB.= `.aC= +**ῌ+*+
/0 (+320a) b_DU!Q7 EFcd
1h i&Jjk
GefgHIKLM7 Q7 H0!fgl  +-1ῌ+0-/0 (+320b) bNO&m9_Dnop qr.d sPtuv HIw +, +ῌ+,
Kobayashi, T. and Kagiyama, T. (+322) Kirishima Volcano Guide book of post-conference scientiﬁc excursions,Kagoshima International Conference on Volcanoes
Volcanol. Soc. Japan +ῌ++
Kobayashi, T., Aramaki, S., Watanabe, T. and Kamada,21

M. (+32+) Kirishima Volcano In IAVCEI symposiumﬁlde excursion guide to Sakurajima, Kirishima and Aso
Volcanoes Volcanol. Soc. Japan +2ῌ-,
ῌQxR  (+331)  !y,z)
{|} +3, ,*2ῌ,+.
~ST (+331) ,.UV[>&a) 8 ,.UVW8pE*UK[=  3Sῌ.
X `Y.Zf`Y.ZfK ,-ῌ,2\] (+30/) ^T_Q +, ,+ῌ-+  .`F.
abEtuv (+332) czd abEtuve   ++ ,/,p+f,g (,**.) hi JI&U .H> ++-, -.3ῌ-2,
? @j (+321) IE*klU%
&m! 8no% p q  --, +13ῌ+22
D% r (+300) _s Tephra s.  00, +/ῌ--tu (+3,,)  0  E -fvZ
=  30 +ῌ/2
 w (+32/) I&a)!exU -*, -+/¡y ¢ (,**,  z£AB{ - 4 C s
 .+, ,,/ῌ,-0
 8.U
Okuno, M., Nakamura, T. and Kobayashi, T. (+332) AMS+.
C dating of historic eruptions of the Kirishima, Sakurajima and Kaimondake volcanoes, southern Kyushu,
Japan Radiocarbon, .*, 2,/ῌ2-,
|}¤ (+3+2) & AB&¥ S -fvZ =  20, +11ῌ+3*
~ ¦$§~? (+3/1) / 4 + 03 il ¨O 0 K /2p V /0, /0ῌy  (+300) .U
1.
(+331) !©_D U U
ª,8 + --ῌ11
Stuiver, M., Reimer, P. J., Bard, E., Beck, J.W., Burr, G.S.,
Hughen, K.A., Kromer, B., McCormac, F.G., van derPlicht, J. and Spurk, M. (+332) INTCAL 32 radiocarbon
age calibration ,.,***-*cal BP Radiocarbon, .*, +*.+ῌ+*2-T«¬­= (,**-) Lzd%,8z®z)
%¯y°±²³2JjabEe  (+)% TE   +*, +/2p?´/0 (,**/) [>NW ,**- +, {*+&E*!µ¶
8E*  /*, .1/ῌ.23·¸¹  º»  

(+33.) F¼®9 (+) - .  03,,.+ῌ,//
Walker, G.P.L. (+31-) Explosive volcanic eruptions -a newclassiﬁcation scheme Geol. Rundsch., 0,, .-+ῌ..0  ¸