ῒΐ  .3  (,**.)
 /  ,-1ῌ,.2 ῕ ῔ ,3**
,**-  +*  ,  ,**.  2  ,- A Large-scale Collapse Event at the Eastern Slope of Fuji Volcano
about ,3** Years Ago
Naomichi MIYAJI῍, Shigeko TOGASHI῍ and Tatsuro CHIBA῍
A large-scale collapse occurred at the eastern slope of Fuji volcano about ,3** years ago, based on calibrated
C age of a wood sample collected in the resulting debris avalanche deposit. The collapsed slide deposit, called“Gotemba debris avalanche deposit” (Goda), is distributed on the eastern foot of the volcano covering an area ofmore than /- km,. The source amphitheater is not preserved because it became covered by younger tephra
erupted from the summit crater. This avalanche deposit is overlain by the “Gotemba mudﬂow deposits” (Gomf)
emplaced repeatedly after the avalanche. Some ﬂow units of the Goda and Gomf entered pre-existing rivers andwere ﬁnally emplaced as ﬂuvial deposits. The Goda is composed of debris-avalanche blocks, showing jigsaw
cracks, along with smaller blocks ranging from several tens of centimeters up to + m in diameter. The
debris-avalanche matrix is a mixture of smaller pieces of blocks and ash-sized materials due to mainly shearing andfragmentation of large blocks. Igneous rocks include fresh and altered gray basaltic lava, weathered tephra
including red scoria and white clay. Petrographical and geochemical data indicate that most blocks were derived
from the Older Fuji volcano. The volumes of the Goda and Gomf are about +.*/ km- and *.1+ km-, respectively,
based on presently available geological and borehole data.
Since the blocks of Goda are composed mostly of the products of the Older Fuji volcano and the older stage
lavas of Younger Fuji volcano do not extend to the eastern foot of Fuji volcano, a bulge of Older Fuji volcano musthave existed in the eastern ﬂank of Fuji volcano preventing the older stage lavas to ﬂow to the east. This bulge
collapsed in the form of three blocks from the foot of the mountain. The abundance of hydrothermally altereddeposits in the Goda and the absence of fresh volcanic products within the Goda suggest its origin as a rupture
inside the altered deposits possibly triggered by a large earthquake or phreatic eruption.
Key words : altered deposits, debris avalanche, Fuji volcano, geochemical data, mudﬂow+.

+ῌ ῐ ῎ ῑ ῏ !" #$%&!'()*+,"'()!`>()89:a`bc]def-.IJ
89:`g6>K-V !;<=>$%&-./!0123.4567389:#;<=> ]'()!`>()89:*FGH45J89:

 +32+ ; ?@ A +32.B C89:"DE FGHI

Goda KLbIJ89:Khi-. Fig. +B

J89: Gomf : ?@ +30. KLM3 '()!NGoda !jkV";< eflm efno6p!jE=>89:OP>QRS#TU23VW. ?@kVkqjr]stu#P>v]] wx +320 ; ?@+311B  +32. "XYZ[\]^_ Gomf,*** ()yz{|}"~rO"6kB ,3" 

+/0ῌ2//* &@ h -ῌ,/ῌ.*CYY
College of Humanities and Sciences, Nihon University, -ῌ,/ῌ.* Sakurajousui, Setagaya-ku, Tokyo+/0ῌ2//*, Japan.
-*/ῌ2/01 jqM +ῌ+ῌ+  1stX[\
Geological Survey of Japan, AIST, Central 1, +ῌ+ῌ+Higashi, Tsukuba -*/ῌ2/01, Japan.
,+/ῌ***. fh ¡¢ +ῌ,ῌ,£¤£¥¦Asia Air Survey Co., LTD., +ῌ,ῌ,, Manpukuji,
Asou-ku, Kawasaki ,+/ῌ***., Japan.
Corresponding author : Naomichi Miyajie-mail : miyaji@chs.nihon-u.ac.jp

o(hl@?m¼@nopq

238 




 











 !  "# "$%«G]m Goda 5 6 Gomf C]mN 
OC#%3  Goda CD#E¬^GI:;& ' &"()*+,-.

<C$F% ([ +\2  2 ([ >Fig. ,A "(Goda­_`)"kl   ® >debris-/0 123 45 67

avalanche block ; Ui et al., ,***A

8  95 6:; <=!

>debris-avalanche matrix ; Ui et al., ,***A a°3 >?@" +331A% B Goda CD#

C$FGGe  k l®T ­(H IJb±"¬C ¬²G°C³% (E:; <C$FBG[ + . /  - (["( ´ ® H 0 0C12KCEBGL%G M%IB" &N(' (<$O" P)QR*+)*+,-ST,U#V.5

H -! Goda

6I/C% W Goda

CD#E:; <C$F 
Gk l¯< cT" +2 0­I;56:; <C$F% 120(dµ ¶#5
6U/#C·¸ X O,e >?@" +331A

H

f%

 !   !  CXY%-(I#0V."Z1 C[H2
% 3 +* 4\+.+ 4]^57"( ,.. 4_6 Tn ` >78@4a +310A-ῌ+ 

P"( w ¹  S-+., Gomf,
S-+/ῌ4 >g@

b`cbd Ge . f9:Gg" +311A% Goda ( Gomf h i S-+. C

 >h@" ,**,A% & +.+ 4cb ^5 Gomf Cº S-+/ῌ

4"(i;jk lC9:3m + fnj#»k Gomf

% Goda ( CH»k3BG%"$ >o( +322A% (&<9:EGpq
rsCt#JBE I9:uDCT!EBG(
=r>vw x? y@"$%5 

 5@z{|}~(A BC3DEB( e >Ui
et al., ,*** ; 8@" ,**,A k>Debris flowA G

!F(GGk5 6HI6@ 
C(H >eJ > @" +31.A
 KL"( Goda FC i;jk l GE%,  ' (<$O P)QR*+ )*+,-ST,
H Goda 5 6 Gomf M | N OC#% W ' (<$OC
P QRP
(" '

]S /**\+/** mT Goda 5

6 Gomf >MA C#% W P)QR*+

Hw

(U(UC$O Goda  V >|
A GX&W(UC X|C#% Y¡¢"(£r>v&¤G¢¥¦)*+,-SC2HWG >Y¡¢(£>vy +32-A% IB" $O>§(Z3 3* ([)*+,-$O¨SC©\ ' (<$OªFig. +. Study area and distribution of the Gotemba
debris avalanche deposit (Goda). Dotted areashows the distribution of the older stage lava
ﬂows of Younger Fuji Volcano (after Miyaji,+322).

 B³V ,3** d.16%Y¼
    

A : N -/,,῍+/ E +-2/0῍+/  Goda 





239

-ῌ, ῐ῏ῌ῍῎Goda gG| Gomf =># ?6 Goda  , m  /* cm B@ A`'" BCC !"#$%&'"() *"+#,

!"-.

 2 cm /01234a() *R Goda *

(uDf /**+*** m E

56 789:;<=3>6) ?@6 Gomf *"GoBFuDf /** m A *BCD.

 Goda 3G^

EF AMS G(a( Fig. ,)!HI"J ,1+*K./ yrs. B.P. PLD-,,,. L+HG Goda ῌ) *#3$M% &NAGLO'P3QR dpI&k( Fig. -) Goda 

CST,+.,U V ,11/K./ yrs.B.P. L) ' ( Goda IJ<"KL M¡"O+-

ῐV^R /WPXY INTCAL32 Stuiver et al., +332 (W

g+n Goda ¢N¡£¤LGG

PZ[\<] CALIB ..- Stuiver and Reimer, +33-¥"() ?* ¦O§¨= ©ª\«G Goda3)^OF_6@A (WP# cal BC 3+/ +s$ Mk ?P¬$­¡"(*`®QG(*` cal BC 3.*ῌ23* L) *#+o% m f^R3M{c¯ Goda $°(+,a(V b-c!" ,3** d.16

V+,6) ¢$S3G

e/I$f^) g hi0+" Goda #3

RGR+Hk(c¯o *GRc¯6

jk12lm( ^n"o(WP3QLO^

w6w±V²TU³´a() g Fig.
-  Gomf 35jk Gomf GEV3G¥"µ

^!HI"J#()Gomf p^O q3 ,-0*K+** yrs. B.P. Gak3.-, : 4 +30. V$0+"O^() ' r tu w+

5svx6 ,.0 yYz^¡"O^uDf /** m  Goda 



o6)

B : N -/,+῍*GR+H@A-¶k ·R+0, E +-2/1῍+2 G456 Gomf 1!Hῌ῎G¥" ῎I"J ,/2*K0/ yrs. B.P. N-.*20 L) *῏VῐG¥" ῍ῐG¥"("+2 d +-C #78({$M%&NA

V+,6) !6 ῏Vῐ¸¹78

'PgG|(WP}9() !6 ~6() g KL$º E.O§

(WPd Goda #V:W6O(V ·3»a(KL,8 ¸¹

+ Goda .1 ,**MkL)-** ,, Gomf 3

o+6;<$.16V+"()·WX  ,* -* m f¡ / m dFig. ,. Locality of outcrops and geological map of the Goda and the Gotemba mudﬂow deposits (Gomf). Gomf
are subdivided into Gomf-m (mud ﬂow deposit) and Gomf-f (ﬂuvial deposit).

» ¨²@¼©ª²«¬­240



y$$%Y|}+M&z{3Do bGomf-fc  | bFig. ,c }~ Gomf-m   ./* m  Goda <$ 56758--  +* m

 /* m    !"#ῌ$ %& ' (()*+,  (*$-$-.

!"#/012



3

¤$

Gomf-f $-$-Wo ^&%_^' Gomf (44jUpqSk_Goda   +*c m 4 m 

567

58 (589!" #:;<$2

G£/$2tQ ¡¢=;<$  +    <    5 o  ;  $=$>?@A567B%4

 Goda 9C&+D'$2=(=Goda (E)*'FG7+H,-./I+) 9a"BQ+l  3PjUp
qSOP_f /Y+* cm $+xjE N q -* 9) Gomf-m  fY > f  x E ; ¥ '  $  N q  ,* Y /*  )  
Gomf-f 

a"$  jUpqSOPy^&

3(01) JK 23L%_B s$ t&iu^- Gomf-m

2=()' 44D'FM563NO +* m )h&i+$ Gomf-f ¦0=,-.PQ4 Goda 56758z[ %RSTUV7+8$ 9 :"&JKbFig. /c<) W  X ,Y- m 

=

W

&i§
  M

Gomf-f @d4o©

 .2 m 3
 4 P

w

Z["\9;]<$2='>^_,yw¨0=M$ 9;B-$ `?aV7)M%ªM=2  $+*'FM

bFig. .c@dA@deBCf*D«D,-. 0=M3@dgE& bFB : F +30.c h-i=GHIJ

$& b +30-c y¨0=¨,%gj\&/I$ (A@dk@d-. b¬ +32* ;  +32+c =$¨$

KL.+lM3m& nN+o1 jUpqS& b  +32.c  Gomf pX2t' bFOP< QrRSsT_SPJK+UV+30. ;  +320c (=Q) Gomf-f or3

$2t' (^_<JKWuv^' FB +X

 Gomf-f w .* m &i+3

wYZx,  A@dKL.

b­ +33.c

567,-.yz[\,-. Goda t^{ Gomf M ( jUpqSOP FB. 

]C|}%,-.uv2=)~=

567,-.56758®J

2 ^&%_+N$2 Goda y Gomf K^'$2 ¯@° a : A±%>fd5

4`4+a"$ ¯@° b : XwYA ¡>fd5 ¯@° c : e(_ Goda  56758bcd²%$

mf³´pµ ¯@° d : %$

>f5ye $ 4  jUpqSSP

d5 ¯@° e : [$%$2xE

+f_+g$h=,-.ij

yd5 / bc |  .5675$¨¢f+g3

= ( ^&%_^' Goda (8¶¯@°KL.4 (_44jUpqSk_+) 9a¯@° a ·qq£¸¤5=$¥<¹£<¹£"BQ+l  3P jUpqSOP>f·qq£¸¤5 =Q)·qq£% f mf+Hf+g$ QrRSs^+ mm 9 <£%  ,Y- mm  ¯@nopY+83q N q /* ° b ·qq£¸¤57 ·qq£%  /Y-* cm $+$&5675]8or3a"$  jUpqSOPy^&%_B s$ t&iu^-
M 



+Y, mm, <£% .Y/ mm  X

%$2= ¯@° c ·qq£¸¤5%³´pµ ·qq£%  +Y, mm, <£% YvEw  Goda &i -* m ] ,Y- mm ' ºbFig. /c2= t ³´pµ¦³´pµ§d$

Gomf B%fe

W

%$

>%=$#%

2  +* cm )h8+D3)) ¯@° d Y|}+\o bGomf-mc  #yxE

¥<¹£·qq£¸¤5=$·qq£¸¤5_`aº ,3** "j#02a»$¼

241

Fig. -. Map showing the extent of ﬂow units of Goda, based on landform analysis of aerial photographs. Gomf
covering Goda are stripped in this map.

[&\[ C./ b'cdY e'f gh#%&iJK[&\+*+ῌ jk# JK2lmn&\[ B- Qop3qQ rCD

qs 3

2 #) rCD qs tE uvwQx2 CDq d y e ,ῌ Qz{)/ Q|2}~ 

3 Table + 2 ) 
3 x rCD qs 3n
YA >  =>' f$

Fig. .. Outcrop of a hummock of Goda at Loc.-,
Kamikobayashi, Gotemba City. Symbols, a, c,d and e show the di#erent types of debrisavalanche blocks.

 Table + _`agh#  JK +*ppm  _`a87n +** ppm Q{z33

#  T  %#  
,

+

, mm,

- mm     e 

!"#

"   



+

+

, mm,

 

#d # Q;2-'3|{ f(, mm $%&'( #)  e *+ ,,-
./0123456789:9;<

@ zA

**

+*cm =>?*'@A

B*3CD EFGH CD<IJK#' LM X NJKO P Q/ 



#*Q¡WH¢£3¤&¥¦§9¨3©# Fig. 0 ª« + 2  ae ¢'¬­®#* ¯°@¤&Q±H z¡W¤&o²f#
*  ³´T G+ G-  - £ f H#

C#%&  R8STUVWXCY

5m³´T G+

 ZW JK[&\[./ ]K'^ ( e ' /*ῌ Q°@ z d '¸!Hn _`a%& b ³´T G,'2@ ZW JK2yµ¶·A#¹?87( c ' /*ῌyixy242

Fig. /.

Table +.

  

Isopach map of the Goda and Gomf based on borehole and ﬁeld data.

Major and trace element concentration of debris-avalanche blocks in the Goda.

a, d/*ῌ  

#$% &' e 

G-  !"G- 

Zr = Y OTUVWZrῌY 'A\]^*XYKLFZU[P
XY  _`aa

 e 

bcC"DdWeY#YFfUgY% hijk()*+ ,-./ ῌ ῍ lmn8MN ,.. o;pqg Tn klrOPc

G+ ,-./῎ ῏



d

G, ,-./ῐ0"12 !"%stu# ZrῌY  -.* #$Fv!UY wixyz +331{% 2MN
Y| -.* #$Fa, b, c  ZrῌY! } ,.. o;pOP0ῌ ῒ῔῎῍ῐῒῑ῏ΐ῕~YF% _3450"16780"129:;<

#$F !} ,.. o;p"YQpmn=>?@ABCD"EF GH%IJKLMN ZrῌY ;< OPQRS"%d, e  Zr ῌ Y  -.*8FG! wFig. 1{%~ijklFhijklmn8#

:'MN¦v§ ,3** jlhi !¨©

243

 Fig. 2,

Sxyz{ |}NqJ.~}eFCob$

Table +    SiO, 

678 a [NqJ.e )* 678

SiO,     TiO,  K, O   

 !"#$ %&'(& TiO,  K, O d, e  ZrῌY  SiO,  TiO, <'= K, O o )* +,-$ +331  Goda ./ 01.2b ,.. jl345678 a9e :*; SiO,  TiO, < 678 b, c  ZrῌY ob678 d, e '(&Cml%Ctub1'= K, O 38>?@ $ +,- +331 AB

nB1 f!$ pqJ.vwSxy ~}$1!C%DE3F1G

|} QRMRSxy `ab1 %

H#IC$ 678 a J.$ 678 d,qJ.HvwSxy[}

e %J.KLM$ 678 b, c 678 aC~}$ QRMRSxy[ + mm

C678 d$ e NOPDEC 

3 rs,-$ +332 C*3 ;<($<$ QRMRSTUVW$ XYZ'([\ T]C^_/ mm

1b678 b, c  ;* ;$ 6`ab1 $ -]cd5Cef(^_ gb1

78 b, c %q

*

 !

./

01hijk|} &)*C,3** jlCmnB1FC

ob$ 678 a J.N&pqJ.

1ῌ ῎

῍

++***92*** jl ; rs$ +322 f!NqJ. ./**9

Goda <'= Gomf 3$ .^ Fig. , $-*** jl ; rs$ +322 Ctub1 pqJ.vw¡?@ Fig. - <'=¢£¤¥ Fig. / 3&

Fig. 0. Percentages of debris-avalanche blocks for each type at the studied eight outcrops. Gomf covering Goda
are stripped in this map. Types of debris-avalanche blocks ; type-a : fresh and porous lavas (olivine basalt,
two-pyroxene basalt), type-b : fresh and dense lavas (olivine basalt), type-c : weakly altered tephra (olivine
basalt), type-d : weakly altered lavas (clinopyroxene bearing olivine basalt, olivine basalt), type-e : heavily
altered tephra and lavas (clinopyroxene olivine basalt, olivine basalt)

µ=¶·¸&¹(º¸»)¼*

244

Fig. 1. Zr vs. Y of lavas from debris-avalanche
blocks. Data of volcanic rocks from Older andYounger Fuji volcano are after Togashi et al.
(+331). Symbols show the types of debrisavalanche blocks.

 Goda +.*/ km , Gomf

 /* km, - /- km, *.1+ km   Goda -   !"#$ % & '( .

)*!+,-Gomf /+012 3

Fig. 2. TiO, and K, O vs. SiO, of debris-avalanche
blocks in the Goda. Outlined areas of volcanic
rocks from Older and Younger Fuji volcano areafter Togashi et al. (+331). Symbols show thetypes of debris-avalanche blocks.

4 

& 5 6789:6;<=4  >.#+?@ABCD EFig. -F 78GHIJD EFig. /F
K

?@ABL

Goda?@ABN#M0+OP

Table ,. Volume of the Goda for all units andtypes of debris-avalanche blocks.

KM
?@ABN#M0+#+Q HIKRS0 N#M
HI PT&'U&VW#X+YZ?@AB HIK[ \-*].*ῌ K^$

K^$ ?@AB῏?@AB῎ ῐ?@ABῌ῍ +*]+/ῌ,ῌ M ETable ,F. % ?@AB_`#_a =b
cd  EFig. 0F KefgO_`#Kcd
_`#_a hL K (0)i _`# j0_`#_a2ῌ ῒ῎ῐ῍ῑ῏)= KY$. )=bK"cd!07   k lmn!

 k  # )=_`#_a#+ opq[ 0 % [erW ?@ABLZcd
Kst %Ks0_`#\
cd L Ks
%

uvw d

.-ῌ K^$ . uvw e{|}~ *.,3 km , uvw c_`#4"x_ *../ km- \yzx_KM

!" +/**]-*** m # +=<=$$ %3

K 3%)!  # )=

!0+-  #+$ ¡ )¢ !
 '( £#¤%¥ ¦§ E,***F¨x

 V©lK>ª«¢"K )0  *.,, km- %  #++ E+F «¢K>ªOP _`#_a¬ *.*2&­®«¯° _{®± ²³>. '-*!+_uvw a, b

km , *.*+ km -"M ETable ,F--( -" E,F &­®«¢-*** '´:;<=L ,3** "#$56&'W%

 1** m    ,**,  ! ,3** "#$245

Wa 2&p Y$KL& xs0(<$ q&'V%&'($)* +  +,-./012$(

3 4567'%89(:;<=

+ 0f(qGg\V K  +,Goda 4'&'W%*%!

>?894 -*** m @ABCD* 2 klm c*

:; ( 01

,L(2 :;s$56&'

23 EFGHI  >J89KL M L W% $ {?K2{'!n +32** m, N?O H  ,//* m LP +, HῌL

&' ¡¢?* :;<$(£2)

( *.+- 2 * Q + km- 4R 0123

, ¤ :;¥ EFGnoD * + ¦§qr ¥HῌL

S( *.*/T*.+- UV  Siebert et al., +321 W
F +.*/ km- LP -./0123/X +( Mf-, ¨© +311 :;¥ ῌ  +320

HῌL

Y-+,,-- Yª +33, «¬  Yr ¥ ( Mf-

S YZ$P' * K' [? +/**T-*** m 4%\- ¨© +311 :;¥ ῍  +320 Y-+-- Y& Fig. , 4$%] F4 2.2* km BC&

ª +33, «¬* " (qr ¥  ,..T

+ SL +.*/ km- 4^D  %] _`a( ++3,.* "# Yr +./T+.. "#m bc

C  ­ p ®!2&¯°(0123 EF,*#dLeC&'0123 0f g\h %8L(>Y!$i:;

jGLP

klm a no& p qr$:;s klm b, c  $p

qr$(:;ts

'eC

klm d, e EF&Fig. 3* klm au)(#v w

i:; xs 0,2 s 0(y)z,&,no&2,{'Fig. +* s0<=$|}~no&2,{'

&

GLP

¥

EFGe

Yª +33,* D2V§:; <=L(£2) ,..T,.* "# +./T+.. "# W%4g+&',* Goda $( ,.. "#2&p # jGK  +,Goda 4&'%

$(+  ,  %L(2,{'<= :;W ®!%&'

* :;±]$²³ ´µ=L(+.0T+.. "# :;s$W%6¶'

s 04j&' <$:;$h 8+,$ ?KP s 0(+ :; W ?

p %/¸(,L(2* + '¹:;±]K4 q&'+

* + $&

xs 0  $(i:; W:; 

Fig. 3.

· ,**+ 

L(K3 {':; W ?K i:; Wq$ºD¡¢(»CL¼2*

Schematic proﬁle of Fuji volcano at the time of the landslide about ,3** years ago.

º(;RG»w¼xy@z

246
3 

+ defg SS-+*$ ++T$ Odefg SOsT %N

 1P S-3 Kb>

 Godah$ 1>"H -r*+ !"# !ῌ$ ῍ %&'( G+  ,qH  Q5 ,$ -/**-*** #)  ! *+),-. /0KaRStw)5$v/,z$

 - 



 1$ 1 !


234





/

4567,8/,,q 7,8 VW( e ,q,
123 $ >?2TK5

  !ῌ" !῎$ ῏ %&'( G, 

 Q5 )1$ 1  !ῌ$ ῍94U -*** #K1$v$ V0/z: ;$ 1<==%&'( G- )>?@AB !ῐ,:CD  ! , E

>$$ K5,q,Ir5

,q,Ir1  + $7OW(S $ OdefgABV0,qq*X3 SYZ$ ,***T +[FFG5  H ;1

SZ\]$ ,*** ; O[T ,K 1

5$  ,IJ K$ @Lmt,MN; OP Q, !ῌ$ ῍ ^Q,$ K923:$ R5>?,_`5V0,q,Ir5 7,

῎$ ῏ :$ @9@4,!

 V0,q>? -sz CD$

 !ῐ:   SFig. 3T 1 -a(.0uv1,<= ?

  5 @9 ,@4=H$  !

, 1 ¡ Ga7FG

ῐ UKVW( d ),

bE3

 .-ῌ !N a <=k1 K46 S

OP

QU0KX",YZ[ \]!^_]`a+32* #$a54%N

SVoight et al., +32+T b$&cdefgVW( c );',%&'( G, *+1$ )0 Kh:d-*** #K/b?$ 1/,G¢]$ ,**,T Ac S+33*T

deK f4*oKb?$SgI£¤5 , 7,6
b$ %&'( G+- *+VW( e ),$ %&'(5j¥¦Y,%N

efg  ( iGjH qhi SFig. 3Tn  KD#$  ,FI§ <=k1 Kl?) $ 
kmn "#@:B*o VW( d$ ep CD +VW( e,q,Ir51-s56?$ =(./t0u

F,,q,Ir5 ¨K$ GF, G+VW( eVW( e >?4,q,Ir51,kl ,$ 1KQ ,z© %N
n 

CD

/F$  9$  / ;mªbn +32. #4aw),  56x7([ SGomf-mT tª  SGomf-fT «zv1>?23

Kl?),p.y $ jH$ :,89z {|}3,Kl?)nS~:$ +321T

CD ;94h¬> Goda ;:(3< ,**-** #­® $oR[,gI CD

1,=146?$  >"%$atO}d! S2$ +332T

%5=

+*

$ ?@A

Gafw)5¯p  °

54 S-+-+/ O}d!t

$ (q±q$ r±qs²t³´=$ ;

B>KCDh:{|}3,%5=n 1$  ^2qqC $ 

U ,3** #K

 SGodaT ,$ + $ ;oR«/>?[-rDE /F$ 2  Ga$
,qH,=I%Nµ¶`·¸u  1$ 1>?Gaf 

J,qH-/**-*** #K$a{|}56 S-3$ LMN

 SGomfT ,  Z*K Goda +.*/km-, Gomf*.1+ km- 5$ HῌL*.+- ¹4

Goda 'Ga,q {|}tv8 ,3** $           
           -  !"  

#$

%&

'

 Goda  ()*) +',- Goda .  

/

 0 123  . 
!' 

 6"#

4 5 %& +.+ $7%&8  89 :';(2),#<)= *+  

8 + ,    

#(-> ? . (   @/ 
0 AB C1#0'  )*)D2#EF+6"#H 8

3  G45& . 6, 'I2J789 89:AAG
G  ;<=KL
>M8NAC1#
OP



 

 A

?A@Q.R7'ASA B 89῏

῎!"C!A9 DTE8U FGHIVWXY*J#K$Z6  &  [\W]^_` abc ,#<(!LM abc deN
%fO<P (&gQ$ & abchijklV5RSI$TUdA
mBnVW? XYZF'I
$TU$[#S\X  &  DT(o]^_p`!"C!9>(Q()qnV& rWs(ot*uovY

wW Schmincke, H. p` xFa <bN89y(oczY{!dea f|}ghic
zY+Fjka ,l~89-amnoG)qpq & r%fst rA !cz.  /
! +/ $u0 uovuocz.1w32cz B a,cx'Xsw`3U4pAyzTW] ) !   c z aT 5 N :  { 6 7 J 7 8 |+/-**-*2c K$ 247ῌ ῑ ῐ ῍}~{kGk F 9 a,**,c 
)   :uod;o,**, $iX(3nl ῌ*-,ῌP*+/.
 k<67kr =k{67kmFk]km> a+311c  z W
 cz +0 21ῌ3*.
]?@7 a+321c A5!%BE#r   5 2 ++-ῌ+,/.
F * a+30.c Tephrochronology #P
CM % aP + ,c o 1- ,3-ῌ-*2 --1ῌ-/*.
F * a+311c  SD y -., p.
F * a,***c LME 2
.0TF(  ,, /*1ῌ/++.
F *kD- a+310c MA
G Tn  VPn  uo .0 --3ῌ-.1.
F * k D- k ]FD- k {67 k mBa+32.c ¡¢l !
ooczdeA¡¢l£w * ¡C¢,  0¤£dA
H uo_0k¤/uo 20/ῌ3,2.
¥m¦ a+32.c §¥I¦ /B5 % J /1A -1ῌ/0.
¢¨ a+32+c ©! !
o ªl ++ 13ῌ2*.
¢¨ a+32.c  %
 a§ªc  ,3 +./.
¢¨ a+322c x%  3. .--ῌ./,.
¢¨k¨^Kk©Fªk«Lk{67k¬«M a+332c {m­UVWXY*®  }o' 8uo}gczYczN¬ /2 +*/ῌ+,*.
DTE9:J a+32-c DTEVWXY*­-Ql
Siebert, L., Glicken, H. and Ui, T.(+321) Volcanic hazards
from Bezymianny- and Bandai-type eruptions. Bull.
Volcanol., .3, .-/ῌ./3.
Stuiver, M. and Reimer, P. J. (+33-) Extended +.C databaseand revised CALIB-.* +.C age calibration program, Radiocarbon, -/, ,+/ῌ,-*.
Stuiver, M., Reimer, P. J., Bard, E., Beck, J. W., Burr, G.
S., Hughen, K. A., Kromer, B., MacCormac, F. G., vander Plicht, J. and Spurk, M. (+332) INTCAL32 radiocarbon age calibration, ,.,***ῌ* cal BP. Radiocarbon,.*, +*.+ῌ+*2-.
®F¯k°F±kOP ¯kQ{@k° Ra,**,c vY²k³iY´ +32* $ %&,#<± +32. $ %&µx¶·¸s²$
 .1 +ῌ1.
S<T¹ a+30-c U³V ,´}
P $5¤  J -0 ,.ῌ.+.
FWºk¢¨k»Tµkr¶- a,***c r·- % !o ,*** $¸¼(3nl 0/.
<¹µ a+32+c º»/B % º»¼X%Y  2345

248

 / 3,῍++1.
  +32*    .+ .῍+-.
 
 +331   !"#$ !%&'()*)  +, -. !/0!1" 2345*67 8#+$%& !
., .*3῍.,+.
Togashi, S. (+323) XRF analytical Report +/23, Determination of major elements in igneous rocks using Sc/Mo
dual anode tube. Geological Survey of Japan, Open-ﬁleReport, +-,, +῍-/.
'( ) +33*  !*+ 9 :;<,-./,+ : S=,/>Y=++., ?* @ +0 -῍,2.
'( )  01 A     2345  67
8BC901DE#:; +33, F!<= :;<>G ?* @ +1 -῍--.
Ui, T., Takarada, S. and Yoshimoto, M. (,***) Debris
avalanche. In Encycloperia of volcano (Sigurdsson, H.,
Houghton, B. F., McNutt, S. R., Rymer, H. and Stix, J.
eds.), Academic Press, London, 0+1῍0,0.
Voight, B., Glicken, H., Janda, R. J. and Douglass, P.M.
(+32+) Catastrophic rockslide avalanche of May +2. U.S.
Geol.Surv., Prof.Pap., +,/*, -.1῍-11.
!HC?@IA?@BAC7DE +31. J
KL!FM,GH IN, JK *O ,,* p.
!PQ L  ,**+  !
R
STM : NO!PU 2345*VWQX YR
SZ?T[ ,**+ U\VJ[W]X Jn*+2.
!PQ L^_C ,**,  ! 8`
abM  !, !cd Y W!, ef Y,. 0.*῍0...
!gZ +33. h [\]& h[R,^_` +῍+**.
01DE# +320 iab<= iabc& ?
* @ +, ,+῍-+.
-deAjfk +332 glmno ! +0.* U!hFp ! .- +-1῍+.2.
n

32.0-ῌ %I|v a(3 / {

\

|!o|'

  32./3ῌ + ,-y *.+/ῌ {'  y%} w X | !oyz wklxm yz wsm
yz DMvu( atdpq r !oJB+A !o} 32.-3ῌ U' Togashi +323  JB+A

L |!o%~L$M' MM  !o root mean square #$no M(h !o}+ ,-yU *.*2ῌ U(C+ XRF !o%tuv} !o~L yJu }Tm|#$noU( 8vULy%Jaw X | !oz

U( %£¤#$ Al, O-, MgO,

U *.,ῌ
Na, O{¡( SiO,}8¢U} + ,-y





Ju

¥¡$M( 

SiO, ~L u rvM$ y{ SiO,

}

 

\}y{¥|v , ,-yU%~(y*.2ῌ q^ ¦§$M( D' wsmyz }¨©{

|auªLM$ y~L}(#% uq'  #$ «%kl|aur !o\M *.2ῌ q''b\}

+**ῌ

'(.} wklxmz t~¬ wklxm yznoU(
'b| 

no}!oIU}au$ dpqU} wklxm yz#­{®p|vu($M' wyz %}'¯ #$no M(y{$#%¡(§ °J($% VCTm|{~u'CT !oUL #± vt~¬x%~²³vu(r´ jsU( U zI$a wkl
xm yz

&%?J(®p%v%¡(µ{¶±

Togashi +323 },-r JB+A {~uv {TM| x{JKv - %|'b\at dpq !o%{'vq^ +iU r B-

js%tuv wklxm

yz {no|' dpqU} Togashi +323 %rukl|aur{sm|v XRF %~L!o|' b\ 3 %r}t +*** DUkl M 
u% vw&M( %~LxmJ( V% , x - %a(vy|\ wklxmz%z{J( rv !o \

+**ῌ

M

.} wklxmz wklxm yz w X | !
oyz wsmyz} u %a(

 !7.

8{. |',-r JB- {V%!o|'  ,-r%±uv§ x{JKv - %|'b\ n\} +**.-/ῌ UL dpq
JB-

r

!o

\!o} +**./.ῌ U'

JB- {}·¸!

²+**ῌ {¡'{¡|vu(x ² 3
¸U( r!o\}  ! 8}

¹ x º+  Ju'

%±uv§'¯

®p

¢\$U

(
`X£{ »¼¤