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8/16/2019 --sutiknobro-16437-1---sutikn-a

1/18

J . G . S . M . V o l . 1 5

N o . 4

N o v e m b e r 2 0 1 4 h a l .

1 6 5 - 1 8 3

1 6 5

L O N G S O R A N R A K S A S A

G U N U N G

A P I

M E R A P I

Y O G Y A K A R T A -

J A W A

T E N G A H

G I G N T I C

L A N D S L I D E S

OF M E R P I

V O L C A N O Y O G YA K A R T A

C E N T R A L J A V A

O l e h :

S u t i k n o

B r o n t o

u

,

A n t o n i u s R a t d o m o p u r b o

u

,

P u d j o A s r n o r o

d a n

M a l i a

A d i t y a r a n i

2 >

' ' P u s a t S u r v e i G e o l o g i , j l n . D i p o n e g o r a 5 7 B a n d u n g

4 0 1 2 2

" A l u m n u s T e k n i k G e o l o g i , U G M

Y o g y a k a r t a

E - m a i l : s b r o n t o @ g r d c , e s d m . g o . i d ; s u t i k n o b r o n t o @ g m a i l . c o m

Abstrak

L o n g s o r a n r a k s a s a m e r u p a k a n l o n g s o r a n s a n g a t b e s a r k e r u c u t g u n u n g

a p i

k o m p o s i t

k e

a r a h t e r t e n t u s e h i n g g a

m e m b e n t u k k a w a h b u k a a n t a p a l k u d a , y a n g d i h a d a p a n n y a t e r l a m p a r e n d a p a n b e r b e n t u k t o p o g r a f i g u m u k . P e n y e l i d i k a n

l a p a n g a n d i d a e r a h G o d e a n d a n s e k i t a r n y a , K a b u p a t e n S l e m a n

Y o g y a k a r t a

t e l a h m e n e m u k a n e n d a p a n l o n g s o r a n r a k s a s a

d a r i G .

M e r a p i , y a n g m e m b e n t u k t o p o g r a f i g u m u k d i t e p i u t a r a p e r b u k i t a n b a t u a n g u n u n g a p i p u r b a G o d e a n . S e b a r a n s i s a

e n d a p a n l o n g s o r a n M e r a p i

i t u

m e n u t u p i a r e a b e r u k u r a n

2

k m

x 2

k m d a n

k e t i n g g i a n g u m u k k u r a n g d a r i

3 0

m

d i a t a s

d a t a r a n

d i

s e k i t a r n y a . E n d a p a n l o n g s o r a n m a s i h s a n g a t l e p a s , b e r u p a f a s i e s b o n g k a h b e r l a p i s , y a n g t e r s u s u n o l e h

e n d a p a n p i r o k l a s t i k a , a l i r a n l a v a

d a n

e n d a p a n r o m b a k a n . S e l u r u h e n d a p a n m e n g a l a m i f r a k t u r a s i s a n g a t k u a t ,

m e m b e n t u k r e k a h a n g e r g a j i d a n s e s a r m i n o r s e b a g a i a k i b a t g e r a k a n l o n g s o r . E n d a p a n l o n g s o r a n i n i d a p a t t e r a w e t k a n

k a r e n a m e m b e n t u r d a n t e r t a h a n o l e h p e r b u k i t a n b a t u a n

T e r s i e r

G o d e a n . D a r i

G .

M e r a p i s a m p a i

G o d e a n

e n d a p a n

l o n g s o r a n i t u b e r g e r a k s e j a u h 3 0 - 3 5 k m d e n g a n v o l u m e m e n c a p a i 1 0 k m 3 d a n d a e r a h t e r l a n d a m e n c a p a i 3 0 0 k m 2 .

K e

a r a h s e l a t a n , m a t e r i a l l o n g s o r a n b e r u b a h m e n j a d i a l i r a n l a h a r , y a n g m e l a n d a d a e r a h B a n t u l s a m p a i

d i

w i l a y a h P a n d a k ,

b e r j a r a k 5 0 k m d a r i

G .

M e r a p i . D i b a g i a n b a r a t l a h a r m e n g a l i r m e l a l u i K . P r o g o d a n d i s e b e l a h t i m u r m e n g i k u t i

K .

B e d o g .

D i

b a g i a n t e n g a h e n d a p a n l a h a r t e r t a h a n o l e h p e r b u k i t a n b a t u a n F o r m a s i S e n t o l o s e h i n g g a m e n y i s a k a n b a n y a k b o n g k a h

b e s a r a n d e s i t d i w i l a y a h S e d a y u . U n t u k m e n g a n t i s i p a s i t e r u l a n g n y a b e n c a n a k a t a s t r o f i k l o n g s o r a n

G .

M e r a p i p a d a m a s a

m e n d a t a n g d i p e r l u k a n m i t i g a s t y a n g l e b i h s e k s a m a .

K a t a k u n c i : G o d e a n , l o n g s o r a n r a k s a s a , l a ha r , M e r a p i ,

Y o g y a k a r t a

Abs t r ac t

Gigantic landslides

are very

large sectoral collapse

o f

composit e volcanic cones that form horse shoe-shaped craters

facing hummocky topography o f the deposits. In the Godean area, Sleman Regency

Yogyakarta,

th e deposit o f Merapi

gigantic landslide has been found, forming

hummocky topography

in the north

o f

Godean paleo volcanic rocks. The

rest

o f

Merapi lan dslid e deposit co vers

an

area

2 km x 2 km and the

height

o f

hummocks

is l e s s

than

30 m

above

the

surrounding paneplain. The deposit is very loose, as block phases composed o f pyroclasti cs, lava flows and reworked

deposits.

All

the deposits are highly fractured to form jigsaw cracks

a n d

smal l-scale fault displacement. Merapi gigantic

landslide deposits

is

well preserved beca use

i t was

blocked

b y

preexisting

topography o f

Tertiary Godean hiils. Flow

distan ce from M erapi to Godean is about 3 0 - 3 5 km, total volume o f the deposit 10 km3 and covered an area ofca. 300

km2. To the south, landsli de mat erial becam e iaharic d eposits which

are

extend ed

in

the Bantu area

up

to

Pandak,

that

i s

50 km away

from Merapi Volcano.

In the

west part la har flowed down

through

Progo

River,

whereas

in the east

following Bedog River. In the m iddlearea, the lahar deposit s were blocked by hil ls o f Sentolo Formation, leaving some

andesitic mega blocks

in

Sedayu area.

In

order

t o

anticipate catastrophic disaster

due to

future M erapi gigantic

landslides, more intensive

mi t igat ion

efforts should be considered as a necessity.

Key

words:

Godean, gigantic

landslide,

lahar,

Merapi, Yogyakarta

Pendahuluan

K a w a h g u n u n g a p i b e r b e n t u k t a p a l k u d a (horse shoe-

shaped

craters)

y a n g m e m b u k a k e a r a h t e r t e n t u d a n

d i

d e p a n n y a t e r h a m p a r p e r b u k i t a n k e c i l y a n g

m e m b e n t u k t o p o g r a f i g u m u k (hummocky

topography)

t e r s u s u n o l e h e n d a p a n k a t a k l a s t i k a

N a s k a h d i t e r i m a : 1 4 M e i 2 0 1 4

R e v i s i t e r a k h i r : 2 0 O k t o b e r 2 0 1 4

g u n u n g

a p i ,

m e r u p a k a n c i r i b e n t a n g a l a m y a n g

t e r b e n t u k o l e h l o n g s o r a n t u b u h k e r u c u t g u n u n g a p i .

B u k i t k e c i l a t a u g u m u k m e m p u n y a i r a g a m k e t i n g g i a n

1 0

h i n g g a 1 0 0

m d i

a t a s d a t a r a n

d i

s e k e l i l i n g n y a .

D i

a n t a r a n y a s e r i n g d i j u m p a i c e k u n g a n t e r i s o l i r

(isolated depressions). D a l a m b e b e r a p a h a l s u m b e r

l o n g s o r a n y a n g s e m u l a b e r u p a k a w a h t a p a l k u d a

t i d a k n a m p a k l a g i k a r e n a t e r t u t u p o l e h k e r u c u t

mailto:[email protected]:[email protected]


2/18

1 6 6

J . G - S - M . V o l . 1 5 N o . 4 N o v e m b e r 2 0 1 4 h a l . 1 6 5 - 1 8 3

e n d a p a n g u n u n g a p i y a n g i e b i h m u d a . L o n g s o r a n

s a n g a t b e s a r

i n i

d i n a m a k a n s e b a g a i l o n g s o r a n

r a k s a s a (gigantic landslides) k a r e n a m e l i b a t k a n

v o l u m e b a t u a n s e r t a t a n a h y a n g s a n g a t b e s a r

( >

0 , 1

k m 3 ) . D a e r a h y a n g t e r l a n d a j u g a s a n g a t l u a s

( p u l u h a n h i n g g a r a t u s a n k m 2 ) . P a r a p e n e l i t i

t e r d a h u l u m e m b e r i k a n n a m a l o n g s o r a n g u n u n g a p i

s e p e r t i i n i d e n g a n b e r b a g a i

i s t i l a h ,

m i s a l n y a volcanic

dr y

avalanches ( U i , 1 9 8 3 ) , rock slide avalanches

( V o i g h t d m , 1 9 8 1 ; G l i c k e n , 1 9 8 3 ) , d a n volcanic

debris avalanches ( S i e b e r t , 1 9 8 4 ) . D e n g a n

d e m i k i a n l o n g s o r a n g u n u n g a p i d a p a t d i n y a t a k a n

s e b a g a i g e r a k a n m a s s a b a t u a n d a l a m j u m l a h s a n g a t

b e s a r d a r i t u b u h k e r u c u t g u n u n g a p i m e l o n g s o r k e

k a k i

d a n d a t a r a n d i h a d a p a n n y a .

D i

d u n i a , l o n g s o r a n g u n u n g a p i p a d a m a s a s e j a r a h

a n t a r a l a i n t e r j a d i d i G u n u n g a p i ( G . )

U n z e n

p a d a

1 7 9 2 , G . B a n d a i ( 1 8 8 8 ) , k e d u a n y a d i J e p a n g , G .

B e z y m i a n n y ( 1 9 5 6 ) d a n G . S h i v e l u c h ( 1 9 6 4 ) d i

K a m c h a t k a R u s i a , s e r t a G . A u g u s t i n e ( 1 8 8 3 ) d i

A l a s k a A m e r i k a S e r i k a t ( S i e b e r t d r r . , 1 9 8 7 ) .

P e n e l i t i a n

I e b i h l a n j u t t e r h a d a p e n d a p a n l o n g s o r a n

G . B a n d a i d i l a k u k a n a n t a r a l a i n o l e h N a k a m u r a d a n

G l i c k e n ( 1 9 9 7 ) d a n U i ( 1 9 9 7 ) . D i J a w a B a r a t

I n d o n e s i a , l o n g s o r a n G . P a p a n d a y a n t e r j a d i p a d a

1 7 7 2 ( N e u m a n n v a n P a d a n g ,

1 9 5 1 ) .

L o n g s o r a n

g u n u n g a p i p a d a m a s a p r a - s e j a r a h d i I n d o n e s i a y a n g

s a n g a t t e r k e n a l a d a l a h

d i G .

R a u n g

J a w a

T i m u r

( N e u m a n n v a n P a d a n g , 1 9 3 9 ; S i e b e r t d r r . , 1 9 9 7 )

d a n

G .

G a l u n g g u n g

J a w a

B a r a t ( N e u m a n n

v a n

P a d a n g , 1 9 5 1

;

B r o n t o , 1 9 8 9 ) . E n d a p a n l o n g s o r a n

G . G a l u n g g u n g m e m b e n t u k g u m u k s a n g a t b a n y a k ,

d i k e n a l d e n g a n n a m a P e r b u k i t a n S e p u l u h R i b u

T a s i k m a l a y a (The Ten Thousa nd Hill s of

Tasikmalaya).

P e m a h a m a n t e r h a d a p l o n g s o r a n s a n g a t b e s a r t u b u h

k e r u c u t g u n u n g a p i i n i s e m a k i n j e l a s b a g i p a r a a h l i

k e b u m i a n s e t e l a h t e r j a d i l o n g s o r a n y a n g d i s e r t a i

l e t u s a n

M o u n t S t . H e l e n s p a d a 1 8 M e i 1 9 8 0 d i

A m e r i k a S e r i k a t ( G a m b a r 1 ) . B e r h u b u n g d e n g a n

a d a n y a k u b a h l a v a d i p u n c a k M o u n t S t . H e l e n s , y a n g

b e r f u n g s i s e b a g a i s u m b a t , m a g m a t i d a k m a m p u n a i k

t e g a k k e a t a s t e t a p i m e n e r o b o s k e s a m p i n g s e h i n g g a

t e r j a d i

p e n g g e m b u n g a n (bulging) p a d a l e r e n g u t a r a

d i s e r t a i p e n s e s a r a n d i d a e r a h p u n c a k . T e k a n a n

m a g m a s e c a r a m i r i n g y a n g s a n g a t k u a t d a n b e b a n

m a s s a b a t u a n y a n g s a n g a t b e r a t m e n y e b a b k a n

t e r j a d i n y a l o n g s o r a n d i i k u t i e r u p s i t e g a k d a n

m e n d a t a r . B e r d a s a r k a n p e n g a l a m a n b e k e r j a d i

d a e r a h g u n u n g a p i , B r o n t o ( 2 0 0 1 ) t e l a h m e l a p o r k a n

e n d a p a n l o n g s o r a n g u n u n g a p i d i I n d o n e s i a .

G a m b a r

1 .

P r o s e s p e m b e n i u k a n l o n g s o r a n g u n u n g a p i M o u n t S t . H e l e n s ,

d i

A m e r i k a S e r i k a t p a d a 1 8 M e i 1 9 8 0 ( L i p m a n dan

M u l l i n e a u x ,

1 9 8 1 } , y a n g d i j a d i k a n a c u a n l o n g s o r a n

s e b a g i a n t u b u h k e r u c u t k o m p o s i t g u n u n g a p i y a n g d i s e r t a i

e r u p s i l e t u s a n .

D i G .

M e r a p i

J a w a

T e n g a h , v a n B e m m e l e n

( 1 9 4 9 )

m e n y a t a k a n a d a n y a l o n g s o r a n k e a r a h b a r a t p a d a

1 0 0 6

M .

E n d a p a n l o n g s o r a n t e r s e b u t m e m b e n t u k

p e r b u k i t a n G e n d o l d i w i l a y a h K e c a m a t a n S a l a m d a n

M u n t i l a n , K a b u p a t e n M a g e l a n g ,

J a w a

T e n g a h .

P e n d a p a t t e r s e b u t t e l a h d i s a n g k a l o l e h N e w h a l l d r r .

( 2 0 0 0 )

k a r e n a d i p e r b u k i t a n i t u t i d a k d i t e m u k a n

a d a n y a c i r i - c i r i e n d a p a n l o n g s o r a n , s e p e r t i h a l n y a

s t r u k t u r r e k a h a n g e r g a j i (jigsaw

cracks)

d a n d i a t a s

b u k i t t e r d a p a t

s i t u s c a n d i H i n d u , y a n g d i b a n g u n p a d a

a b a d 7 - 8 M . P e n t a r i h k a n d e n g a n m e t o d a K - A r

t e r h a d a p b a t u a n p e r b u k i t a n G e n d o l m e m b e r i k a n

u m u r 3 , 4 j t l . ( j u t a t a h u n y a n g l a l u , N e w h a l l d r r . ,

2 0 0 0 ) . I n i b e r a r t i b a t u a n p e r b u k i t a n G e n d o l b e r u m u r

I e b i h t u a d a r i p a d a u m u r G . M e r a p i , y a n g k u r a n g d a r i

1 0 0 . 0 0 0 t a h u n .

D i b a n d i n g d e n g a n u m u r b a t u a n

g u n u n g a p i d i P e g u n u n g a n K u l o n P r o g o ( 1 2 , 6 -

2 9 , 6 3 j t l . , S o e r i a - A t m a d j a d r r . , 1 9 9 4 ; N g k o i m a n i ,

2 0 0 5 ; P e r m a n a d e w i d r r . ,

2 0 0 8 )

b a t u a n d i

p e r b u k i t a n G e n d o l b e r u m u r j a u h I e b i h m u d a .


3/18

L o n g s o r a n R a k s a s a G u n u n g A p i M e r a p i

Y o g y a k a r t a - J a w a

T e n g a h

1 6 7

3

S i

»1

; Iter

• I

3

KULOMFHOG0

4 \ u

S . ' ' / l • . ' T —

r ut / ; - - f / ,

u

- . 1 2

U

I

K A 0 G U W W G W W A

Aran

sarin

grMaij

G a m b a r 2 _ P et a l o k a s i d a e r a h p e n e l i t i a n ( k o n t a k

h i t a m ) .

ya n g m e l i p u t i d a e r a h

K a b u p a t e n S l e m a n d a n B a n t u l , Y o g y a k a r t a .

O l e h s e b a b i t u B r o n t o

( 2 0 1 4 )

m e n y i m p u l k a n b a h w a

p e r b u k i t a n G e n d o l m e r u p a k a n s i s a g u n u n g a p i p u r b a

s e t e m p a t .

P e r m a s a l a h a n l o n g s o r a n k e r u c u t

G

M e r a p i

d i m u n c u l k a n l a g i k a r e n a d i t e m u k a n d a t a b a r u d i

d a e r a h

G o d e a n

K a b u p a t e n S l e m a n d a n d i s e l a t a n n y a

d i d a e r a h K a b u p a t e n

B a n t u l ,

D a e r a h I s t i m e w a

Y o g y a k a r t a . M a k a l a h

i n i

d i s u s u n b e r d a s a r h a s i l

p e m e r i k s a a n l a p a n g a n s e c a r a b e r k a l a p a d a t a h u n

2 0 1 4 . D a e r a h p e n e l i t i a n t e r l e t a k d i w i l a y a h

G o d e a n

d a n s e k i t a r n y a , K a b u p a t e n S l e m a n d a n K a b u p a t e n

B a n t u l ,

D a e r a h I s t i m e w a

Y o g y a k a r t a

( G a m b a r 2 ) .

H a s i l s e r n e n t a r a m e n u n j u k k a n b a h w a k e d e p a n

G .

M e r a p i m a s i h b e r p o t e n s i l o n g s o r s e h i n g g a p e r l u

p e r h a t i a n I e b i h c e r m a t , b a i k m e l a l u i p e n e l i t i a n I e b i h

l a n j u t

m a u p u n p e m a n t a u a n g u n u n g a p i i t u s e n d i r i .

Tataan G e o l o g i

S e c a r a r e g i o n a l , g e o l o g i d a e r a h

G o d e a n d a n

s e k i t a r n y a t e l a h d i l a p o r k a n o l e h R a h a r d j o d r r .

( 2 0 1 2 )

d i

d a l a m p e t a g e o l o g i l e m b a r Y o g y a k a r t a . B a t u a n

t e r t u a d i m a s u k k a n

k e

d a l a m F o r m a s i N a n g g u l a n

( T e o n ) , y a n g b e r u m u r E o s e n . F o r m a s i i n i t e r d i r i a t a s

b a t u p a s i r d e n g a n s i s i p a n H g n i t , n a p a l p a s i r a n ,

b a t u l e m p u n g d e n g a n k o n k r e s i

l i m o n i t ,

s i s i p a n n a p a l

d a n b a t u g a m p i n g , b a t u p a s i r d a n t u f . D i a t a s F o r m a s i

N a n g g u l a n d i e n d a p k a n F o r m a s i K e b o b u t a k ( T m o k ) ,

y a n g t e r s u s u n o l e h b r e k s i a n d e s i t , t u f , t u f l a p i l i ,

a g l o m e r a t d a n s i s i p a n a l i r a n l a v a a n d e s i t d a n b e r u m u r

O l i g o - M i o s e n . K e d u a s a t u a n b a t u a n t e r s e b u t

k e m u d i a n d i t e r o b o s o l e h

d i o r i t

( d r ) d a n a n d e s i t ( a ) ,

y a n g b e r u m u r M i o s e n B a w a h . L e b i h k e s e l a t a n d a r i

G o d e a n , y a k n i d i d a e r a h K a b u p a t e n B a n t u l , t e r d a p a t

F o r m a s i S e n t o l o

( T m p s ) ,

y a n g t e r d i r i a t a s

b a t u g a m p i n g d a n b a t u p a s i r n a p a l a n b e r u m u r M i o s e n

- P l i o s e n . V o l k a n i s m e K u a r t e r d i d a e r a h

Y o g y a k a r t a

m e m b e n t u k G u n u n g a p i M e r a p i , y a n g m a t e r i a l n y a

d i b a g i m e n j a d i E n d a p a n G u n u n g a p i M e r a p i Tu a

( Q m o ) d a n E n d a p a n G u n u n g a p i M e r a p i M u d a ( Q m i ) .

H a n y a

E n d a p a n G u n u n g a p i M e r a p i M u d a y a n g

s a m p a i d i d a e r a h

G o d e a n

d a n

B a n t u l .

Hasil Penelitian

M e n g a c u t a t a a n g e o l o g i t e r s e b u t

d i

a t a s b a t u a n

d i

d a e r a h

G o d e a n

d a n s e k i t a r n y a d i b a g i m e n j a d i d u a

k e l o m p o k u t a m a , y a i t u 1 . B a t u a n b e r u m u r T e r s i e r

d a n 2 . E n d a p a n

G .

M e r a p i , y a n g b e r u m u r K u a r t e r .


4/18

1 6 8

J . G . S . M . V o l . 1 5 N o . 4 N o v e m b e r 2 0 1 4 h a l . 1 6 5 - 1 8 3

B e r d a s a r k a n h a s i l p e n e l i t i a n , b a t u a n T e r s i e r d i d a e r a h

G o d e a n

d i h a s i l k a n o l e h k e g i a t a n g u n u n g a p i p u r b a

s e t e m p a t , y a n g d i n a r n a k a n G u n u n g a p i p u r b a

G o d e a n .

D i

b a w a h i n i d i p a p a r k a n b e n t a n g

a \ am d a n

b a t u a n h a s i l k e g i a t a n G u n u n g a p i p u r b a

G o d e a n

d a n

G . M e r a p i . E n d a p a n

G .

M e r a p i t e r d i r i a t a s e n d a p a n

l o n g s o r a n d a n e n d a p a n l a h a r .

Gunung

Api Purba Godean

, S e k i t a r

1 0 k m d i

s e b e l a h b a r a t k o t a Y o g y a k a r t a

t e r h a m p a r d a t a r a n G o d e a n

d a n

s e k i t a r n y a , y a n g

m e m p u n y a i k e t i n g g i a n a n t a r a 1 0 0 m - 1 4 0 m

d i

a t a s

p e r m u k a a n

a i r l a u t . D i

d a e r a h d a t a r a n

i t u

t e r d a p a t

d e r e t a n p e r b u k i t a n b e r a r a h u t a r a - s e l a t a n , y a k n i

G u n u n g N g a m p o n

( +

2 2 2

m ) ,

G e d a n g

{ + 1 9 3

m ) ,

G e d e ( + 2 1 8 m ) , B u t a k ( + 1 5 4 m ) , d a n G u n u n g

B e r j o ( + 1 7 5 m ) ( G a m b a r 3 ) . P a d a b a g i a n t e n g a h ,

p u n c a k - p u n c a k b u k i t b e r d e r e t d e n g a n a r a h t e n g g a r a

-

b a r a t l a u t , y a n g d i b e r i n a m a G u n u n g P a t u k ( + 2 3 1

m ) ,

W u n g k a l

( + 1 8 7

m ) ,

G e d e ( + 2 1 8 m ) ,

d a n

G u n u n g S i w a r e n g ( + 1 9 4 m ) . A g a k t e r p i s a h d i

b a g i a n b a r a t t e r d a p a t G u n u n g S o

( +

1 7 3

m ) ,

y a n g

t e r l e t a k d i

D e s a

S i d o r e j o , K e c a m a t a n G o d e a n .

G u n u n g N g a m p o n , y a n g t e r l e t a k p a l i n g u t a r a d a r i

p e r b u k i t a n G o d e a n , t e r m a s u k w i l a y a h D e s a

M a r g o d a d i , K e c a m a t a n S e y e g a n . P e r b u k i t a n

t e r s e b u t s e b a g i a n t e r s u s u n o l e h b a t u a n b e k u

t e r o b o s a n d a n s e b a g i a n l a g i o l e h b a t u a n p i r o k l a s t i k a .

P a d a u m u m n y a b a t u a n b e k u t e r o b o s a n

i t u

m e r u p a k a n p e n y u s u n b u k i t - b u k i t y a n g I e b i h t i n g g i

d i b a n d i n g p e r b u k i t a n y a n g t e r s u s u n o l e h b a t u a n

p i r o k l a s t i k a .

S e l u r u h b a t u a n p e n y u s u n p e r b u k i t a n

i t u

s u d a h m e n g a l a m i p e l a p u k a n s a n g a t

l a n j u t

m e n j a d i

t a n a h J e m p u n g d a n t e r t u t u p o l e h v e g e t a s i l e b a t .

S i n g k a p a n b a t u a n s e g a r h a n y a d i t e m u k a n p a d a

l o k a s i p e n g g a l i a n t a n a h d a n b a t u .

B a t u a n b e k u t e r o b o s a n p e n y u s u n p e r b u k i t a n

G o d e a n

a d a l a h a n d e s i t p o r f i r i - d i o r i t m i k r o , s e b a g i a n b e s a r

t e l a h t a p u k m e n g u l i t b a w a n g ( G a m b a r 4 ) . P e l a p u k a n

l a n j u t b a t u a n b e k u i t u m e n j a d i t a n a h l e m p u n g

d i m a n f a a t k a n o l e h p e n d u d u k s e t e m p a t u n t u k

p e m b u a t a n g e n t i n g d a n b a t a m e r a h . I n t i p e l a p u k a n

k u l i t b a w a n g b e r u p a b o n g k a h

s e g a r

d a r i a n d e s i t

p o r f i r i -

d i o r i t m i k r o b e r u k u r a n 0 , 5

m - 2 m ,

b e r b e n t u k m e m b u n d a r . S e c a r a u m u m , b a t u a n b e k u

t e r o b o s a n

i t u

b e r w a r n a

s e g a r

a b u - a b u s a m p a i

a b u -

a b u k e h i j a u a n t e r k l o r i t k a n , b e r t e k s t u r p o r f i r i d a n

b e r s t r u k t u r p e j a l . F e n o k r i s t e r d i r i a t a s p l a g i o k l a s

b e r u k u r a n 1 - 5 m m , k e l i m p a h a n 2 0 - 3 0 % d a n

p i r o k s e n b e r u k u r a n 0 , 5 - 1 m m , k e l i m p a h a n 5 - 1 0

G a m b a r 3 p e t a s e b a r a n p e r b u k i t a n d i w i l a y a h G o d e a n d a n s e k i t a r n y a ,

K a b u p a t e n S l e m a n , D a e r a h I s t i m e w a Yo g y a k ar t a . S u m b e r :

P e l a r u p a b u m i s k a l a

1 :

2 5 . 0 0 0 , l e m b a r

j 4 0 8 - 2 2 3

Y o g y a k a r t a d a n l e m b a r

1 4 0 8 - 2 4 1

S l e m a n ( B a k o s u r t a n a l ) .

% .

K e d u a f e n o k r i s i t u t e r t a n a m

d i

d a l a m m a s s a d a s a r

a f a n i t . A n d e s i t p o r f i r i d a n d i o r i t m i k r o d e n g a n m a s s a

d a s a r a f a n i t t e r s e b u t , y a n g m e m b e n t u k b u k i t - b u k i t

t e r p i s a h m u l a i d a r i G u n u n g N g a m p o n d i s e b e l a h

u t a r a s a m p a i d e n g a n G u n u n g B e r j o d i b a g i a n

s e l a t a n ,

d i y a k i n i s e b a g a i t u b u h - t u b u h b a t u a n b e k u

t e r o b o s a n d a n g k a l . B a t u a n t e r s e b u t m e r u p a k a n h a s i l

p e m b e k u a n m a g m a

d i

b a w a h g u n u n g a p i p a d a m a s a

l a l u , a t a u I e b i h d i k e n a l s e b a g a i b a t u a n s e m i g u n u n g

a p i

{subvolcanic intrusive rocks,

B r o n t o ,

2 0 1 3 ) . D i

b a g i a n b a r a t p e r b u k i t a n G o d e a n , b a t u a n t e r o b o s a n

a n d e s i t p o r f i r i

{diorit mikro)

t e r s i n g k a p

d i

G u n u n g

S o

( +

1 7 3 m ) ,

D u s u n C e l u n g a n , D e s a S u m b e r a g u n g ,

K e c a m a t a n M o y u d a n p a d a k o o r d i n a t 0 7 ° 4 4 ' 1 5 , 1 "

L S

- 1 1 0 ° 1 5 ' 5 8 , 7 " B T .

S i n g k a p a n b a t u a n

i t u

b e r u p a

i n t i p e l a p u k a n b e r s t r u k t u r k u l i t b a w a n g , b e r b e n t u k

m e m b u l a t , b e r u k u r a n

1 - 3

m . A n d e s i t p o r f i r i

s e g a r

b e r w a r n a a b u - a b u t e r a n g , b e r t e k s t u r , b e r s t r u k t u r

m a s i f ( p e j a l ) . F e n o k r i s t e r d i r i a t a s p l a g i o k l a s ( 3 0

% } ,


5/18

L o n g s o r a n R a k s a s a G u n u n g A p i M e r a p i Yo g y a k a r t a

- J a w a

T e n g a i

1 6 9

G a m b a r 4 . K i r i a t a s : G . N g a m p o n d i f o t o d a ri s e l a t a n d i j a l a n

G o d e a n

- S e y e g a n , k o o r d i n a t S G T 4 4 '

3 3 4 , 8 " -

E

1 1 0 1 7 ' 4 3 , 3 " ,

L P

1 7 .

K a n a n at a s s i n g k a p a n b a t u a n b e k u a n d e s i t d i D u s u n N g a m p o n ,

D e s a

M a r g o d a d L

K e c a m a t a n S e y e g a n , K ab u p a t e n S l e m a n Yo g y a k a r t a , k o o r d i n a t S 0 7 ° 4 4 ' 1 4 . 3 " - E 1 1 D " 1 7 ' 4 7 , 3 " . K i r i

b a w a h :

S t r u k t u r m e n g u l i t b a w a n g d a r i b a t u a n b e k u . K a n an b a w a h : C l o s e u p b a t u a n b e k u s e g a r b e r w a r n a

a b u - a b u t e k s t u r p o r t i r i .

p i r o k s e n ( 1 0 % ) d a n h o r n b l e n d a d % ) , b e r u k u r a n 1 -

3 m m , t e r t a n a m d i d a l a m m a s s a d a s a r a f a n i t . D i

d a l a m

t u b u h t e r o b o s a n a n d e s i t p o r f i r i i n i d i t e m u k a n

x e n o l i t g e l a s g u n u n g a p i d a n f r a g m e n a n d e s i t ( 5 % ) .

S e b a g i a n b a t u a n t e r o b o s a n s u d a h m e n g a l a m i

s i l t s i f i k a s i , k a o i i n i t i s a s r d a n l i m o n i t i s a s i , s e r t a

t e r b e n t u k u r a t - u r a t k u a r s a .

B a t u a n g u n u n g

a p i

t e r d i r i a t a s b r e k s i p u m i s

d a n

t u f ,

y a n g d i y a k i n i s e b a g a i b a t u a n p i r o k l a s t i k a , t e r s i n g k a p

d i b e b e r a p a t e m p a t ( G a m b a r 5 ) . D i b a g i a n b a r a t

b a t u a n

p i r o k l a s t i k a i n i t e r s i n g k a p d i d u a t e m p a t d i

d e k a t

G u n u n g S o , y a k n i d i D u s u n J e r i n g ,

D e s a

S i d o r e j o , K e c a m a t a n G o d e a n , k o o r d i n a t

0 7 ° 4 4 ' 3 8 , 0 " L S -

1 1 0

a

1 6 ' 2 0 , 9 "

B T d a n d i D u s u n

C e l u n g a n , D e s a S u m b e r a g u n g , K e c a m a t a n

M o y u d a n ,

k o o r d i n a t 0 7 ° 4 4 ' 4 5 , 4 " L S - 1 1 0 ° 1 6 '

0 9 , 6 " B T . D i b a g i a n t i m u r b a t u a n p i r o k l a s t i k a i t u j u g a

t e r s i n g k a p d i D u s u n P e n d e k a n d a n u t a r a D u s u n

K a n d a n g a n , s e r t a d i k a k i G u n u n g

G e d a n g , D e s a

M a r g o d a d i , K e c a m a t a n S e y e g a n , K a b u p a t e n

S l e m a n . S e d a n g k a n d i b a g i a n s e l a t a n p e r b u k i t a n

G o d e a n

t u f

d i j u m p a i

d i

G u n u n g W u n g k a l ( k o o r d i n a t

0 7 ° 4 4 ' 4 4 , 6 " L S - 1 1 0 ° 1 6 ' 4 8

P

8 " B T ) d a n b u k i t +

1 5 3

m ( k o o r d i n a t 0 7 ° 4 4 ' 5 4 , 1 " L S - 1 1 0 ° 1 6 ' 4 4 , 4 "

B T ) , D u s u n M l o y o r e j o d a n J o m b o r a n ,

D e s a

S i d o r e j o ,

K e c a m a t a n G o d e a n . B r e k s i p u m i s s a n g a t d i d o m i n a s i

o l e h

b u t i r a n p u m i s b e r b e n t u k m e n y u d u t , b e r u k u r a n

k e r i k i l a t a u l a p i l i s e h i n g g a s e c a r a g e n e s i s m e r u p a k a n

b a t u a n

p i r o k l a s t i k a y a n g d i n a m a k a n b a t u l a p i l i

p u m i s . P a d a u m u m n y a b r e k s i p u m i s i n i s u d a h l a p u k

b e r w a r n a p u t i h , k u n i n g c o k l a t , d a n y a n g s u d a h l a p u k

l a n j u t m e n j a d i t a n a h b e r w a r n a c o k l a t k e m e r a h a n . D i

D u s u n P e n d e k a n s e b e l a h b a r a t , b r e k s i p u m i s b a g i a n

b a w a h n a m p a k m a s i f , d e n g a n t e b a l k e s e l u r u h a n

I e b i h k u r a n g 2 0 m . K a d a n g - k a d a n g d i d a l a m b r e k s i

p u m i s

d i j u m p a i f r a g m e n

l i t i k ,

b e r u k u r a n b u t i r r a t a -

r a t a 1 - 3 c m , m a k s i m u m 1 0 c m , b e r b e n t u k s a n g a t

m e n y u d u t s e p e r t i d i t e m u k a n d i D u s u n P e n d e k a n

p a d a k o o r d i n a t 0 7 °

4 4 ' 3 1 , 4 "

L S - 1 1 0 °

1 7 ' 0 2 , 5 "

B T .

F r a g m e n l i t i k

i t u

b e r k o m p o s i s i a n d e s i t , b e r w a r n a

a b u - a b u g e l a p , b e r t e k s t u r g e l a s , a f a n i t s a m p a i p o r f i r i

h a l u s , d a n b e r s t r u k t u r p e j a l h i n g g a b e r l u b a n g h a l u s .

P a d a b a g i a n a t a s b r e k s i p u m i s b e r s e l a n g - s e l i n g

d e n g a n t u f , d e n g a n t e b a l p e r l a p i s a n b e r a g a m a n t a r a

5 - 3 0

c m . T u f

t e r d i r i a t a s

t u f

k a s a r ( b a t u p a s i r

t u f )

d a n t u f h a l u s b e r w a r n a m e r a h u n g u s e d a n g y a n g

a g a k l a p u k b e r w a r n a m e r a h c o k l a t .


6/18

1 7 0

J . G . S . M . V o l . 1 5 N o . 4 N o v e m b e r 2 0 1 4 h a l .

( 6 5 - 1 8 3

G a m b a r 5 A l a s : B a t u l a p i l i p u m i s d i D ' i s u n J e r i n g , D e s a S i d o r e j o , K e c a m a t a n G o d e a n , k o o r d i n a t

0 7 '

1

4 4 ' 3 3 , 0 " L S - 1 1 0 1 6 2 0 , 9 " B T ( k i r i ) d a n b a t u l a p i l i p u m i s b e r c a m p u r d e n g a n f r a g m e n

l i t i k

a n d e s i t s a n g at m e n y u d u t ( k a n a n ) d i D u s u n P e n d e k a n , D e s a M a r g o d a d i , K e c a m a t a n

S e y e g a n ,

k o o r d i n a t

0 7

r

4 4 ' 3 1 , 4 " L S - 1 1 0

e

1 7 ' 0 2 , 5 " B T. B a w a h : P e r l a p i s a n

b a t u l a p i l i

p u m i s

d a n t u f d i D u s u n C e l u n g a n ,

D e s a

S u m b e r a g u n g . K e c a m a t a n M o y u d a n , k o o r d i n a t

0 7 " 4 4 '

4 5 , 4 "

L S - 1 1 0 °

1 6 ' 0 9 . 6 "

B T ( k i r i ) d a n t u f h a l u s m e r a h u n g u d i k a k i G u n u n g

G e d a n g ,

t e n g g a r a D u s u n K a n d a n g a n , D e s a M a r g o d a d i , K e c a m a t a n S e y e g a n , k o o r d i n a t

0 7 * 4 4 ' 5 6 , 4 "

L S - 1 1 0

n

1 7 ' 2 6 , 6 " B T .

G a m b a r 6 A t a s : Tu f t e r s i l i k a ( t t ) m e n j a d i b a t u a n a t a p d i a t as b a t u a n b e k u ( b b ) ( k i r i ) d a n x e n o l i t t u f

t e r s i i i k a

( It ) d i d a l a m b a t u a n b e k u ( b b ) ( k a n a n ) , k o o r d i n a t

0 7 M 4

3 4 , 3 "

L S

- 1 1 0 '

J

1 6 ' 4 5 , 7 "

B T. B a w a h : E le k p a n g g a n g t u f t e r s i l i k a ( h i t a m ) p a d a k o n f a k t u f t e r s i l i k a ( t t ) d e n g a n b a t u a n

b e k u ( b b ) ( k i r i , k o o r d i n a t D 7

P

4 4 ' 3 0 , 9 " L S - 1 1 0

;

1 6 ' 4 6 . 7 " B T) d a n t u f m e n g a l a m i

s i l i s i f i k a s l

k a o l i n i t i s a s i d a n l i m o n i t i s a s i d i t e m p a t p e m a k a m a n u m u m K a b u p a t e n S l e m a n ,

k a k i t i m u r G u n u n g G e d e , k o o r d i n a t

0 7

c

4 4 ' 4 8 , 4 "

L S -

I 1 0

1 7 ' 0 1 , r

B T . K e e m p a t n y a

t e r l e t a k d i l e r e n g l i m u r l a u t G u n u n g G e d e , D u s u n P e n d e k a n , D e s a M a r g o d a d i , K e c a m a t a n

S e y e g a n .


7/18


Y o g y a k a r t a

- J a w a

T e n g a h

1 7 1

P a d a l e r e n g

t i m u r

G u n u n g G e d e t u f m e m b e n t u k

b a t u a n a t a p {roof pendant) d i a t a s b a t u a n t e r o b o s a n ,

d a n s e b a g i a n m a s u k s e b a g a i xenolit ( G a m b a r 6 ) . D i

k a k i t i m u r

G u n u n g G e d e t u f k a s a r m e r a h c o k l a t y a n g

d i t e r o b o s o l e h b a t u a n b e k u m e n i m b u l k a n e f e k

p a n g g a n g p a d a k o n t a k n y a , b e r w a r n a

h i t a m

d a n

b e r s u s u n a n s i l i k a j u g a .

D a r i u r a i a n t e r s e b u t

d i

a t a s m a k a b a t u a n g u n u n g

a p i

p u r b a

G o d e a n

t e r d i r i a t a s b a t u a n p i r o k l a s t i k a y a n g

d i t e r o b o s o l e h b a t u a n b e k u t e r o b o s a n . B a t u a n

p i r o k l a s t i k a

t e r d i r i a t a s b a t u l a p i l i p u m i s , t u f k a s a r

d a n

t u f

h a l u s , y a n g s e b a g i a n s u d a h t e r u b a h

u t a m a n y a m e n j a d i

t u f

t e r s i l i k a

d a n

a r g i l i k . B a t u a n

t e r o b o s a n d i d u g a m e m b e k u d i d a l a m d a p u r m a g m a

a t a u k a n t o n g m a g m a d a r i G u n u n g a p i p u r b a G o d e a n ,

s e h i n g g a d i n a m a k a n b a t u a n t e r o b o s a n s e m i g u n u n g

a p i .

B e r d a s a r k a n p e n a m p a k a n

f i s i k d i

l a p a n g a n

d i p e r k i r a k a n p a l i n g t i d a k a d a t i g a t a h a p

p e n e r o b o s a n . B a t u a n t e r o b o s a n t e r t u a k e a d a a n n y a

s u d a h t e r u b a h k u a t d a n m e n e m p a t i d e r e t a n G u n u n g

G e d e .

P e n e r o b o s a n k e d u a t e r j a d i j u g a d i G u n u n g

G e d e ,

y a k n i d e n g a n t e r s i n g k a p n y a b a t u a n t e r o b o s a n

b a s a l , y a n g s u d a h t e r s i l i k a s a n g a t k u a t . P e n e r o b o s a n

k e t i g a m e m b e n t u k G u n u n g B e r j o , B u t a k ,

G e d a n g ,

N g a m p o n , G u n u n g S o d a n B u k i t + 1 5 3 m d i s e b e l a h

s e l a t a n G u n u n g

G e d e .

M a g m a t i s m e t a h a p k e t i g a i n i

d i d u g a j u g a m e n e r o b o s

d i

G u n u n g

G e d e

d a n

t e r s i n g k a p

d i

D u s u n K l e b e n . S e c a r a u m u m

p e n e r o b o s a n m a g m a p a d a t a h a p k e t i g a t e r s e b u t

d i c i r i k a n o l e h p e n a m p a k a n y a n g m a s i h s e g a r ,

s e k a l i p u n d i d a l a m i n t i p e l a p u k a n m e n g u l i t b a w a n g ,

S t r u k t u r g e o l o g i b e r u p a k e k a r , p a d a u m u m n y a b e r a r a h

U t a r a - S e l a t a n ( N 1 7 0 ° - 1 8 0 ° E ) , d i j u m p a i d i G u n u n g

N g a m p o n , G e d e , B u t a k

d a n

G u n u n g B e r j o . A r a h

i n i

a g a k n y a s e s u a i d e n g a n b e n t u k s e b a r a n p e r b u k i t a n d i

d a e r a h

G o d e a n

d a n s e k i t a r n y a . P o l a u m u m k e k a r d a n

k e m u n c u l a n b a t u a n t e r o b o s a n , y a n g b e r a r a h u t a r a

-

s e l a t a n , m u n g k i n d i k o n t r o l o l e h s i s t e m s e s a r n o r m a l d i

d a l a m

graben

B a n t u l - Y o g y a k a r t a ( B a r i a n t o , 2 0 0 9 ) .

G a m b a r 7 m e n y a j i k a n p e t a s e b a r a n b a t u a n

d i

d a e r a h

G o d e a n

d a n s e k i t a r n y a .

Endapan

Longsoran

Raksasa

G M erapi

D a r i h a s i l p e n e l i t i a n d i t e m u k a n t a n d a - t a n d a l o n g s o r a n

r a k s a s a G . M e r a p i d i d a e r a h G o d e a n , K a b u p a t e n

S l e m a n , Y o g y a k a r t a . S e b a g i a n e n d a p a n l o n g s o r a n

t e r s e b u t t e r a n g k u t m e n j a d i l a h a r , y a n g t e r s i n g k a p

d i

d a e r a h K a b u p a t e n B a n t u l d a n t e p i b a r a t K a l i P r o g o ,

K a b u p a t e n K u l o n P r o g o , Y o g y a k a r t a . D i t e p i u t a r a

p e r b u k i t a n

G o d e a n

t e r d a p a t s e b a r a n g u m u k

UMUR

SATUAN BATUAN

Kuarter

. Endapan Later ft Almlum G M erapi

:

Endapan Longsoran C Msrap

:

Daluan TenXramn

Am u Porta

CMoK Mfco

: Bout Lapili Fumii 1 Tuf

G a m b a r 7 P e t a s e b a r a n b a t u a n

T e rs i e r G o d e a n

d a n b a t u a n K u a r t e r d a r i

G . M e r a p i d i d a e r a h

G o d e a n

d a n s e k i t a r n y a , K a b u p a t e n

S l e m a n , D a e r a h I s t i m e w a Y o g y a k a r t a .

(hummocky topography), y a n g I e b i h r e n d a h d e n g a n

r a t a - r a t a k e t i n g g i a n a n t a r a

1 4 2 - 1 4 6 m d i

a t a s

p e r m u k a a n

a i r l a u t ,

t e t a p i k u r a n g d a r i

3 0

m t e r h a d a p

d a t a r a n

d i

s e k i t a r n y a .

D i

b a g i a n

t i m u r

t o p o g r a f i g u m u k

b e r a d a d i u t a r a G u n u n g

G e d e ,

s e d a n g k a n d i s e b e l a h

b a r a t t e r l e t a k d i u t a r a G u n u n g S o ( G a m b a r 8 ) .

G u n u n g

G e d e

d a n G u n u n g S o m e r u p a k a n b a g i a n d a r i

b a t u a n g u n u n g

a p i

p u r b a G o d e a n y a n g b e r u m u r

T e r s i e r

d a n s u d a h l a p u k l a n j u t . S e b a r a n g u m u k i t u d a r i

t i m u r

k e b a r a t d i m u l a i d a r i D u s u n P e n d e k a n d a n

J l e g o n g a n ,

D e s a

M a r g o d a d i , K e c a m a t a n

S e y e g a n

s a m p a i D u s u n D u w e t , J a t e n , d a n S u n t e n

D e s a

S e n d a n g r e j o , K e c a m a t a n M i n g g i r , b e r j a r a k I e b i h


8/18

G a m b a r 8 S e b a r a n b u k i t - b u k i t k e c i l

(hummocky topography)

y a n g

tersusun

o l e h e n d a p a n l o n g s o r a n G u n u n g a p i M e r a p i

di

s e b e l a h u t a ra b u k i t - b u k i t s i s a G u n u n g a p i p u r b a G o d e a n ( G .

G e d e

d a n G . S o ) .

Atas:

buKA k e c i l d i s e b e l a h t i m u r

D u s u n J l e g o n g a n ( k i r i ) d a n b u k i t (B t . ) J l e g o n g a n ( + 1 4 5 m , k a n a n ) d i s e b e l a h u t a r a G u n u n g ( G . ) G e d e . K i r i bam n:

B t . Surlen ( + 1 4 3 m ) d i s e b e l a h u t a r a G . S o , k o o r d i n a t 7 ' 4 4 1 0 , 7 " L S - 1 1 0 ' 1 6 3 8 . 0 " B T. K a n a n b a w a h : S e b a r a n

b u k i t - b u k i t

k e c i l {hummocky topography) m u l a i d a ri b u k i t ( B t . ) J l e g o n g a n ( t i t i k + 1 4 5 m ) s a m p a i d e n g a n B t .

P l a n g g o k , d i f o t o d a r i l e r e n g utara Gunwg ( G . ) G e d e , k o o r d i n a t 7°

4 4 3 4

7 " L S - 1 1 0 ° 1 6 ' 4 5 , 1 " B T. k a m e r a

m e n g h a d a p k e u t a r a .

k u r a n g 2 k m . K e a r a h u t a r a sebaran g u m u k masih

d a p a t d i i k u t i s a m p a i D u s u n P l a n g g o k , D e s a

M a r g o k a t o n , K e c a m a t a n S e y e g a n , j u g a s e p a n j a n g

I e b i h k u r a n g

2

k m .

P a d a u m u m n y a d i p e r m u k a a n g u m u k m a t e r i a l b e r b u t i r

h a l u s s u d a h l a p u k m e n j a d i t u b u h t a n a h , t e t a p i

b o n g k a h a n d e s i t d a n

b o m

s k o r l a m a s i h

s e g a r d a n

t e r s e b a r s e c a r a a c a k ( G a m b a r 9 d a n 1 0 ) . P a d a p u n c a k

g u m u k d i D u s u n D u w e t t e r d a p a t a r t e f a k b e r u p a y o n i .

I n i m e m b u k t i k a n b a h w a a b a d 7 - 8 M d a e r a h i t u t e l a h

d i h u n i

o l e h m a s y a r a k a t b e r a g a m a H i n d u . E n d a p a n

k l a s t i k a g u n u n g a p i y a n g m a s i h s e g a r d i j u m p a i p a d a

l o k a s i p e n g g a l i a n

d i Dusun

D u w e t

d a n Dusun

P e n d e k a n .

K h u s u s d i D u s u n P e n d e k a n b e n t u k b e n t a n g

a l a m g u m u k m e m a n j a n g

berarah utara

t i m u r l a u t

-

s e l a t a n

b a r a t d a y a m e n e m p a t i r u a n g d i a n t a r a g u m u k

b a t u a n y a n g I e b i h t u a y a n g b e r a r a h b a r a t - t i m u r , d a r i

D u s u n P e n d e k a n s a m p a i d e n g a n K a n d a n g a n .

D i

D u s u n Pendekan, D e s a M a r g o d a d i , K e c a m a t a n

S e y e g a n e n d a p a n l o n g s o r a n G u n u n g

a p i

M e r a p i ,

m a s i h

m e m

p e r l i h a t k a n s t a i k t u r p e r l a p i s a n

(intact

strata) e n d a p a n k l a s t i k a g u n u n g a p i ( G a m b a r 1 1 ) .

D i

d a l a m

oer\ ap \ san

e n d a p a n t e r s e b u t

a d a

e n d a p a n

p i r o k l a s t i k a ,

e n d a p a n r o m b a k a n d a n a l i r a n l a v a y a n g

m e n g a l a m i f r a k t u r a s i sangat k u a t , b e r u k u r a n b u t i r

h a l u s

( a b u )

s a m p a i k a s a r ( b o n g k a h ) ; senng

d i t e m u k a n s t r u k t u r r e k a h a n g e r g a j i

(jigsaw

cracks)

d a n s e s a r m i n o r . E n d a p a n p i r o k l a s t i k a

dicmkan

o l e h

a d a n y a b o m

gunung

a p i d a n s k o r i a

d i

d a l a m m a t r i k s

a b u d a n l a p i l i g u n u n g a p i d e n g a n p e m i l a h a n b u r u k .

E n d a p a n rombakan b e r b u t i r k a s a r m e n g a n d u n g

b o n g k a h - b o n g k a h m e m b u n d a r s e b a g a i a k i b a t

t e r a b r a s i s e l a m a p e n g a n g k u t a n

d a n

y a n g b e r b u t i r

h a l u s

m e m b e n t u k s t r u k t u r p e r l a p i s a n t i d a k m e n e r u s .

E n d a p a n r o m b a k a n t e r s e b u t d i p e r k i r a k a n s e b a g a i

e n d a p a n s u n g a i p a d a l e r e n g b a w a h a t a u k a k i g u n u n g

a p i s e b e l u m m e n g a l a m i p e r p i n d a h a n t e m p a t s e b a g a i

a k i b a t

g e r a k a n l o n g s o r a n , A l i r a n l a v a s u d a h b e r b e n t u k

b o n g k a h - b o n g k a h b e s a r b e r k o m p o s i s i a n d e s i t ,

b e r u k u r a n 1 - 2 m .

Endapan l o n g s o r a n G . M e r a p i t e r s e b u t d a p a t

t e r k o n s e r v a s i d e n g a n b a i k k a r e n a m e m b e n t u r d a n

tertahan k e m u d i a n m e n g e n d a p p a d a l e r e n g d a n k a k i

p e r b u k i t a n G u n u n g a p i p u r b a Godean bagian utara.

S e c a r a u m u m g e r a k a n a l i r a n g r a v i t a s i l o n g s o r a n

b a t u a n g u n u n g a p i d a r i u t a r a i n i d i t u n j u k k a n o l e h

bentuk

t o p o g r a f i g u m u k b e r a r a h u t a r a

-

s e l a t a n m u l a i

d a r i D u s u n P l a n g g o k s a m p a i D u s u n J l e g o n g a n .


9/18

L o n g s o r a n R ak s a s a G u n u n g A p i M e r a p i

Yo g y a k a r t a - J a w a Te n g a h

1 7 3

G a m b a r 9 K i r i a t a s : t a n a h p e r m u k a a n y a n g s u d a h l ap u k b e r w a r n a c o k l a t - c o k l a t

h i t a m

d a n d i g a l i u n t u k b a h a n g o n t in g / b a t a m e r a h .

K a n an a t as : B a g i an b a w a h t u b u h t a n a h m e n g a n d u n g b o m k e r ak r a t i d a n b l o k g u n u n g a p i y a n g m a s i h s e g a r d a n

b e r s t r u k t u r s k o r i a .

B a w a h : s i n g k a p a n b a t u an y a n g m a t r i k s n y a a g ak l ap u k n a m u n t r a g m e n n y a

r e l a t i t

m a s i h s e g a r . L o k a s i

b u k i t

+ 1 4 5 , D u s u n J l e g o n g . D e s a M a r g o d a d i . K e c a m a t a n S e y e g a n , k o o r d i n a t

0 7

a

4 4 1 3 , 3 "

L S

- 1 1

( H 6 ' 5 2 , 0 " B T .

G a m b a r l O

K i r i :

B o n g k a h an d e s i t s an g a t b e s a r, b e r u k u r a n 8

m d i d e k a t p a t o k t i t i k

k e t i n g g i a n b u k i t i 1 4 5 m , k o o r d i n a t 0 7

l

' 4 4 ' 1 1 , 3 "

L S - 1 1 0 ° 1 6 5 2

;

4 " B T, D u s u n J l e g o n g a n , D e s a M a r g o d a d i , K e c a m a t a n S e y e g a n , K a n a n a t as : S i n g k a p a n e n d a p a n

l o n g s o r a n G u n u n g a p i M e r a p i m e n g a n d u n g b o n g k a h s an g a t m e r u n c i n g , D u s u n S u n t e n , D e s a S e n d a n g r e j o ,

K e c a m a t a n M i n g g i r , k o o r d i n a t

T 4 4 0 5 , 1 " L S —

1 1 0 °

1 6 ' 3 4 , 1

" B T . K a n a n b a w a h : b o n g k a h a n d e s i t b e r d i a m e t e r 4 , 5

m

d i

p u n c a k g u m u k , D u s u n J at c n ,

D e s a

S e n d a r i g r e j o . K e c am a t a n M i n g g i r , k o o r d i n a t

V 4 3 ' 5 6 , 1 "

L S - 1 1 0 °

1 6 ' 2 3 , 9 "

B T .


10/18

1 7 4

J . G . S . M . V o l . 1 5 N o . 4 N o v e m b e r 2 0 1 4 h a l .

1 6 5 - 1 8 3

S e c a r a l o k a l g e r a k a n a l i r a n j u g a d i t u n j u k k a n o l e h

b e n t u k m e m a n j a n g g u m u k P e n d e k a n , y a n g b e r a r a h

utara tim udaut ~ s e l a t a n baratdaya k e m u d i a n m a s u k

d a n b e r h e n t i

d i

a n t a r a

deretan

b u k i t k e c i l

batuan

G u n u n g a p i p u r b a G o d e a n . D e r e t a n b u k i t k e c i l

batuan

y a n g I e b i h

t u a

i t u b e r a r a h b a r a t - t i m u r , m u l a i d a r i

D u s u n P e n d e k a n s a m p a i d e n g a n

t i t i k

k e t i n g g i a n

+

1 6 1 m d a n + 1 4 9 m d i b a r a t l a u t d a n u t a r a D u s u n

K a n d a n g a n . S t r u k t u r s e s a r m i n o r d i d a l a m e n d a p a n

l o n g s o r a n ,

y a n g b e r a r a h N 2 9 5

p

E / 7 0 ° ( G a m b a r 1 1 ) ,

j u g a m e n d u k u n g a d a n y a

g a y a

g e r a k a n d a r i

Utara-

T i m u r l a u t .

P a d a s a a t t e r j a d i l o n g s o r a n d e n g a n

g a y a

d o r o n g y a n g s a n g a t k u a t d a p a t m e n i m b u l k a n s e s a r

n a i k d e n g a n j u r u s t e g a k l u r u s a r a h g a y a . S e b a l i k n y a ,

j i k a a l i r a n s u d a h b e r h e n t i d a n b a t u a n m e n g a l a m i

pemadatan, gaya menurun

b a h k a n b e r b a l i k a r a h , b i s a

t e r j a d i

s e s a r n o r m a l dengan \ urus b e r a r a h N N W - S S E .

D e n g a n d e m i k i a n a l i r a n e n d a p a n l o n g s o r a n

G .

M e r a p i

i t u

s e a k a n m e m o t o n g t e g a k i u r u s t e r h a d a p d e r e t a n

b u k i t k e c i l , y a n g b e r a r a h b a r a t - t i m u r . G a m b a r 7

m e m p e r l i h a t k a n

s e b a r a n e n d a p a n l o n g s o r a n

G .

M e r a p i d i

d a e r a h

G o d e a n

d a n s e k i t a r n y a , K a b u p a t e n

S l e m a n , D a e r a h I s t i m e w a Y o g y a k a r t a . D i s e b e l a h

barat

d a n t i m u r p e r b u k i t a n G o d e a n t i d a k d i j u m p a i e n d a p a n

l o n g s o r a n g u n u n g a p i , d e m i k i a n p u l a d i s e b e l a h u t a r a

D u s u n P l a n g g o k . H a l i t u k a r e n a t i d a k a d a t i n g g i a n

batuan tua

s e b a g a i p e n a h a n , s e h i n g g a e n d a p a n

l o n g s o r a n g u n u n g a p i y a n g masih berupa b a h a n l e p a s

s u d a h t e r k i k i s m e n j a d i l a h a r .

Endapan lahar

E n d a p a n l a h a r d i j u m p a i

d i

D u s u n N g l a h a r , D e s a

S u m b e r s a r i , K e c a m a t a n M o y u d a n , K a b u p a t e n

S l e m a n ,

Y o g y a k a r t a , k o o r d i n a t 0 7 ° 4 7 ' 1 3 , 7 " L S -

1 1 0 ° 1 6 ' 0 1

p

4 " B T ( G a m b a r 1 2 atas). D i d u g a , n a m a

d u s u n i t u d i l a n d a s i p e m a h a m a n b a h w a d a e r a h

i n i

p e r n a h t e r l a n d a l a h a r . D u s u n i n i t e r l e t a k

3 k m d i

s e l a t a n a g a k k e b a r a t d a r i

G o d e a n

d i d a e r a h a t i r a n

K a l i B l e n d u n g . K a l i B l e n d u n g m e r u p a k a n h i l i r n y a

K a l i

K r u s u k y a n g m e l a l u i d a e r a h G o d e a n . S i n g k a p a n

endapan lahar terdapat d i d a s a r a l i r a n K a l i B l e n d u n g

d a n d i t e p i s e l a t a n D u s u n N g l a h a r . P a d a l o k a s i k e d u a

i t u

e n d a p a n l a h a r b e r a d a

d i

s a l u r a n a i r d e n g a n t e b a l

lui^vyuiA-W VVjCv l

• j^ n ^5? v/ ^ ^ ^ -^ Ste

G a m b a r

1 1

K i r i a l a s : S i n g k a p a n e n d a p a n l o n g s o r a n G u n u n g a p i M e r a p i , y a n g

m e m p e r l i h a t k a n

p e r l a p i s a n , d i D u s u n P e n d e k a n ,

D e s a M a r g o d a d i , K e c a m a t a n S e y e g a n , k o o r d i n a t

0 7 M 4 2 0 . 2 "

L S - 1 1 Q

3

1 7 0 6 , 4 " B T . D i d a l a m p e r l a p i s a n i t u

t e r d a p a t e n d a p a n p i r o k l a s t i k a ( k a n a n a l a s ) d a n e n d a p a n r o m b a k a n (k i r i b a w a h ) . E n d a p a n p i r o k l a s t i k a d i c i r i k a n

d e n g a n a d a n y a b o m g u n u n g a p i . E n d a p a n r o m b a k a n d i t a n d a i o l e h (r a g m e n b e r b e n t u k m e r u n c i n g t a n g g u n g -

m e m b u n d a r t an g g u n g , k e m a s t e r t u t u p d i t i n d i h e n d a p a n b e r b u t i r I e b i h h a l u s b e r l a p i s t i d a k m e n e r u s , y an g d i d u g a

s e b a g a i e n d a p a n s u n g a i

(duvium)

d i k a k i G . M e r a p i s e b e l u m d i l o n g s o r k a n . K a n a n b a w a h : S e s a r m i n o r d i d a l a m

e n d a p a n l o n g s o r a n b e r k e d u d u k a n N 2 9 5 ' E / 7 Q '

J

.

http://urus/http://urus/http://urus/


11/18

L o n g s o r a n R a k s as a G u n u n g A p i M e r a p i

Y o g y a k a r t a - J a w a T e n g a h

1 7 5

G a m b a r 1 2 A t a s : D u s u n N g l a h ar ( k i r i ) d i d u g a s e b a g a i a s a l - r n u l a n a m a l ah a r k a r e n a p e r n a h t e r l an d a la ha r p a d a m a s a

l a l u

d a n

s e k a r a n g m a s i h

a d a

e n d a p a n n y a ( k a n a n ) L o k a s i

d i

D u s u n N g l a h ar , D e s a S u m b e r s a r L K e c a m a t a n M o y u d a n ,

K a b u p a t e n S l e m a n , Yo g y a k a r t a , k o o r d i n a t

0 7

U

4 7 ' 1 3 , 7

M

L S - 1 1 0 °1 6 ' 0 1 ,4 " B T.

B a w a h : B o n g k a h a n d e s i t , y a n g

m e r u p a k a n s i s a e n d a p a n l a ha r G u n u n g a p i M e r a p i

d i

t e p i b a r a t D u s u n B o b o s a n .

D e s a

A r g o m u l y o , K e c a m a t a n

S e d a y u , K ab u p a t e n

B a n t u l ,

k o o r d i n a t

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4 7 ' 5 7 , 4 "

L S

- 1 1

( T 1 6 ' 2 2 , 0 "

B T .

s i n g k a p a n

1 - 2 m

b e r w a r n a c o k l a t l a p u k . F r a g m e n

l a h a r

b e r s u s u n a n a n d e s i t , m e r u n c i n g t a n g g u n g

-

m e m b u n d a r t a n g g u n g , b e r u k u r a n b u t i r r a t a - r a t a

1 0

- 1 5 c m ,

m a k s i m u m

6 0 c m

t e r t a n a m

d i

d a l a m

m a t r i k s

b e r b u t i r p a s i r - k e r i k i l a g a k p a d u .

D i

s e b e l a h s e l a t a n K e c a m a t a n

G o d e a n d a n

K e c a m a t a n M o y u d a n , K a b u p a t e n S l e m a n , y a n g

b e r j a r a k

4 - 5

k m , y a k n i

d i

w i l a y a h

D e s a

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K e c a m a t a n S e d a y u , K a b u p a t e n

B a n t u l ,

d i j u m p a i

b a n y a k b o n g k a h b e s a r b a t u a n b e k u a n d e s i t , y a n g

t e r l e t a k d i

b a g i a n u t a r a d a n m e n i n d i h b a t u a n F o r m a s i

S e n t o l o

( R a h a r d j o

d r r . , 2 0 1 2 ) . K e

a r a h s e l a t a n d a r i

d a e r a h i n i F o r m a s i S e n t o l o m e m b e n t u k b e n t a n g a l a m

p e r b u k i t a n . B o n g k a h b e s a r a n d e s i t

i t u

t e r s e b a r

d i

D u s u n R e w u l u , W a t u ,

P a n g g a n g d a n

D u s u n S e n g o n

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1 2

b a w a h ) . B a t a s b a r a t s e b a r a n

b o n g k a h b e s a r a n d e s i t

i t u

t e r l e t a k

d i D e s a

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k o o r d i n a t 0 7

o

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n

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o

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b a t a s

t i m u r

b e r a d a

d i

D u s u n W a t u , k o o r d i n a t

( t f ^ f f O l ^ " L S - 1 1 0 ° 1 7 ' 0 5 , 8 " B T .

K e d u a l o k a s i

t e r s e b u t b e r j a r a k I e b i h k u r a n g

3 - 4

k m . B e r d a s a r k a n

i n f o r m a s i d a r i p e n d u d u k s e t e m p a t d a h u l u d a e r a h

i n i

d i n a m a k a n D e s a

W a t u , s e b e l u m m e n j a d i b a g i a n d a r i

D e s a / \ r g o m u l y o . P e n a m a a n D e s a W a t u a g a k n y a

d i d a s a r k a n o l e h b a n y a k n y a s e b a r a n b o n g k a h b a t u

d i

d a e r a h i t u , k a r e n a n a m a w a t u

d i

d a l a m b a h a s a

J a w a

b e r a r t i

b a t u .

B o n g k a h a n d e s i t

d i

w i l a y a h K e c a m a t a n S e d a y u

i t u

b e r u k u r a n m a k s i m u m a n t a r a

2 , 0 - 4 , 7 m ,

b e r b e n t u k m e n y u d u t

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m e m b u n d a r t a n g g u n g .

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s e h i n g g a

d i

D u s u n P a n g g a n g o l e h p e n d u d u k

s e t e m p a t

d i n a m a k a n ' W a t u G a j a h ' .

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a n t a r a

b o n g k a h b e s a r a n d e s i t

i t u

k a d a n g d i j u m p a i m a t r i k s

s e k a l i p u n

s u d a h l a p u k b e r w a r n a m e r a h c o k l a t

b e r b u t i r

k e r i k i l ,

p a s i r s a m p a i l e m p u n g

t a n a h . D i

d a l a m m a t r i k s t e r d a p a t b a n y a k f r a g m e n a n d e s i t

s e g a r

y a n g s u d a h m e n g a l a m i a b r a s i b e r b e n t u k

m e n y u d u t

-

m e m b u n d a r t a n g g u n g d e n g a n k e m a s

t e r b u k a . C i r i

l i t o l o g i

t e r s e b u t m e n u n j u k k a n b a h w a

m a t e r i a l

i t u a d a l a h e n d a p a n l a h a r . S e b a r a n b o n g k a h

b a t u b e s a r d a n s i s a e n d a p a n l a h a r t e r s e b u t u m u m n y a

b e r a d a

d i

t i n g g i a n k e b u n

d a n

p e m u k i m a n p e n d u d u k

d i

t e n g a h - t e n g a h d a t a r a n p e s a w a h a n y a n g s u b u r .

K a d a n g - k a d a n g k u m p u l a n b o n g k a h b a t u

d i

t e n g a h -

t e n g a h s a w a h j u g a d i j u m p a i .


12/18

1 7 6

J . G . S . M . V o l . 1 5 N o .

4

N o v e m b e r

20U

h a l .

1 6 5 - 1 8 3

G a m b a r 1 3 S i n g k a p a n e n d a p a n l ah a r ( e l ) m e n u m p a n g d i a t a s b a t u g a m p i n g F o r m a s i Sento o ( Is ) d i D u s u n S e m b u n g a n , D e s a

B a n g u n j i w o . K e c a m a t a n K a s i h a n , K a b u p a t e n

B a n t u l .

G a m b a r

k i r i

d a n k a n a n a t a s d i f o t o d i k o o r d i n a t 0 7

u

5 0 ' 0 2 , 4 " L S

- 1 1 0 * 2 0 * 2 3 , 3 " B T g a m b a r

k i r i

b a w a h d i l o t o d i k o o r d i n a t u T 5 0 ' O 7 , 1 "

L S - 1 1 0

n

2 0 2 3 , 7 "

B T .

S e b a g i a n b e s a r b o n g k a h a n d e s i t m a s i h s e g a r

b e r w a r n a a b u - a b u , b e r t e k s t u r p o r f i r i

-

a f a n i t , s t r u k t u r

m a s i f -

berlubang

h a l u s , f e n o k r i s b e r u p a p l a g i o k l a s

( p u t i h , k e l i m p a h a n u m u m , berukuran < 1 mm) dan

p i r o k s e n ( h i t a m , k e l i m p a h a n j a r a n g , b e r u k u r a n

< 1

m m ) ,

k a d a n g - k a d a n g a m f i b o l , y a n g t e r t a n a m

d i

da\ am massa d a s a r a f a n i t ,

D a r i ura' tan d i a t a s d i p e r k i r a k a n b a h w a e n d a p a n

b o n g k a h besar a n d e s i t d i d a e r a h S e d a y u m e r u p a k a n

s i s a e n d a p a n l a h a r y a n g t e r a w e t k a n

karena

m e n u m p a n g d a n t e r t a h a n d i l e r e n g u t a r a p e r b u k i t a n

F o r m a s i S e n t o l o . A l i r a n l a h a r y a n g m a m p u

mengangkut

b o n g k a h - b o n g k a h b e s a r a n d e s i t

t e r s e b u t b e r s u m b e r d a r i endapan longsoran G u n u n g

a p i M e r a p i y a n g b e r a d a d i u t a r a n y a , y a k n i d i d a e r a h

G o d e a n

d a n s e k i t a r n y a . D e n g a n d e m i k i a n a s a l m u l a

k e b e r a d a a n b a n y a k b o n g k a h b e s a r a n d e s i t d i d a e r a h

S e d a y u i n i dapat d' tsebandlngkan d e n g a n k e b e r a d a a n

e n d a p a n l o n g s o r a n G u n u n g a p i M e r a p i d i s e b e l a h

u t a r a p e r b u k i t a n b a t u a n g u n u n g a p i p u r b a G o d e a n ,

y a i t u s a m a - s a m a t e r h a l a n g o l e h b e n t a n g a l a m

tmgg)an batuan y a n g s u d a h a d a p a d a w a k t u i t u .

L e b i h

k e

s e l a t a n

-

t e n g g a r a d a r i w i l a y a h S e d a y u ,

y a k n i d i

Dusun

L e m a h d a d i ( k o o r d i n a t 0 7

o

5 0 ' 0 7 , 9 "

L S

- 110°18 '16 ,4 " B T ) d a n Dusun

S e m b u n g a n

( S e m p u ) , D e s a B a n g u n j i w o , K e c a m a t a n K a s i h a n ,

K a b u p a t e n B a n t u l , d i j u m p a i e n d a p a n l a h a r b e r b u t i r

l e b i h h a l u s ( p a s i r - k e r a k a l ) m e n u m p a n g d i a t a s

F o r m a s i S e n t o l o ( G a m b a r 1 3 ) .

D i

l o k a s i i n i e n d a p a n

l a h a r m e n c a p a i k e t e b a l a n 3 - 5 m , t e r k o n s o l i d a s i

l e m a h - p a d u , b e r u p a b r e k s i k o n g l o m e r a t a n d a n

b a t u p a s i r , b e r s t r u k t u r p e j a l . L o k a s i s i n g k a p a n b e r a d a

d i

s e b e l a h b a r a t d a e r a h a l i r a n K a l i B e d o g s e k a r a n g

d a n d i s e b e l a h t \ m ur

Gunung

S e m p u .

Endapan

l a h a r

b e r b u t i r h a l u s i t u m a s i h d a p a t

d i i k u t i

k e a r a h h i H r

K a J j

B e d o g s a m p a i d e n g a n j e m b a t a n y a n g

m e n g h u b u n g k a n a n t a r a

D e s a

P e n d o w o h a r j o

K e c a m a t a n S e w o n dengan D e s a G u w o s a r i ,

K e c a m a t a n P a j a n g a n , K a b u p a t e n B a n t u l , koordinat

0 7

o

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(

7 " L S - 1 1 0

Q

1 9 ' 4 2 , 0 " B T

( G a m b a r

1 4

a t a s ) . D i

t e m p a t i n i t e r d a p a t t u b u h t a n a h p u r b a d a r i

Formas\ S e n t o l o y a n g d i t i n d i h o l e h e n d a p a n l a h a r .

L e b i h k e h i l i r h i n g g a K a l i B e d o g bermuara d i K a l i

P r o g o t i d a k d i j u m p a i s i n g k a p a n

d a n

d a e r a h n y a

m e r u p a k a n d a t a r a n .

D a r i h a s i l p e n y e l i d i k a n g e o l i s t r i k d a n p e m b o r a n a i r

o l e h B a l a i B e n i h I k a n , D i n a s P e r i k a n a n d a n K e l a u t a n

Pemenntah Kabupaten

B a n t u l d i k e t a h u i b a h w a

d i

D u s u n G e s t k a n - K a u m a n , D e s a W i j i r e j o ,

Kecamatan


13/18

L o n g s o r a n R a k s a s a G u n u n g A p i M e r a p i Y o g y a k a r t a - J a w a T e n g a h

1 7 7

G a m b a r 1 4 A t a s : S i n g k a p a n e n d a p a n l a ha r p ad a l e b i n g a l i r a n K a l i B e d o g ( k i r i ) , y a n g m a s i h m e m p e r l i h a t k a n f r a g m e n - f r a g m e n h a l u s

b e r b e n t u k m e r u n c i n g , m e n u m p a n g d i a t a s t u b u h t a n a h p u r b a ( t p ) d a r i b a t u g a m p i n g F o r m a s i S e n t o l o , Lo k a s i d i s e b e l a h

u t ar a j e m b a t a n y a n g m e n g h u b u n g k a n D e s a G u w o s a r i , K e c a m a t a n P a j a n g a n

d i

s e b e l a h b a r a t d e n g a n D e s a

P e n d o w o h a r j o , K e c a m a t a n S e w o n d i s e b e l a h t i m u r , K a b u p a t e n B a n t u l , k o o r d i n a t 0 7 " 5 1

;

2 7 , 7 "

L S - 1 1 0 1 9 ' 4 2 , 0 " B T.

B a w a h : G u n u n g S e n t o n o d i f o t o d a r i s e b e l a h t i m u r j e m b a t a n K l an g o n , k a m e r a m e n g h a d a p k e b a r at ( k i r i ) d a n

p e n a m p a k a n s i n g k a p a n e n d a p a n l a h a r

d i

k a k i t i m u r G u n u n g S e n t o n o a t au t e b i n g b a r a t K a l i P ro g o . Lo k a s i

D e s a

B a n j a r o y o , Ke c a m a t a n K a l i b a w a n g , K a b u p a t e n K u l o n P r o g o , Yo g y a k ar t a, k o o r d i n a t

0 7 ^ 3 8 3 2 , 5 "

L S - 1 1 0 ' M 5 ' 1 5 , 8 " B T .

P a n d a k s a m p a i k e d a l a m a n

1 4 0 m d i

b a w a h

p e r m u k a a n t e r s u s u n o l e h e n d a p a n p a s i r ( l e p a s ) d a n

p a s i r l e m p u n g a n ( A n o n i m , 2 0 1 4 ) . E n d a p a n p a s i r

l e p a s b e r f u n g s i s e b a g a i l a p i s a n p e m b a w a

a i r

[aquifer) b e r a d a p a d a k e d a l a m a n 1 6 , 6 1 - 1 8 , 0 2 m

d i p a n d a n g s e b a g a i a k i f e r d a n g k a l , y a n g b e r a d a p a d a

k e d a l a m a n l e b i h d a r i 4 9 , 4 8

m

d i a n g g a p s e b a g a i

a k i f e r

d a l a m . K e d u a a k i f e r i t u d i b a t a s i o l e h b a t u p a s i r

l e m p u n g a n y a n g d i p a n d a n g s e b a g a i l a p i s a n k e d a p

a i r .

E n d a p a n p a s i r l e p a s b a g i a n b a w a h d a n s a n g a t

t e b a l ( h a m p i r 1 0 0 m ) d i d u g a s e b a g a i p e r p a n j a n g a n

e n d a p a n l a h a r d i d a e r a h h u l u s u n g a i a t a u p a l i n g t i d a k

m e r u p a k a n b a h a n r o m b a k a n l e b i h l a n j u t d a r i

e n d a p a n l a h a r m e n j a d i e n d a p a n s u n g a i p a d a m a s a

l a l u . W i l a y a h P a n d a k K a b u p a t e n B a n t u l

i n i

b e r j a r a k

l e b i h d a r i 5 0 k m d a r i G . M e r a p i . K e a r a h s e l a t a n

e n d a p a n l a h a r t e r s e b u t t i d a k h a n y a m e l a n d a d a e r a h

a l i r a n

s u n g a i K a l i B e d o g

d i

b a g i a n t i m u r , t e t a p i

d i

b a g i a n t e n g a h ( d a e r a h

G o d e a n

-

D u s u n N g l a h a r )

j u g a m a s u k k e

h i l i r

K a l i K r u s u k , K a l i K r u w e t d a n K a l i

B l e n d u n g , y a n g b e r n a m a K a l i K o n t e n g , k e m u d i a n

b e r m u a r a d i K a l i P r o g o . A l i r a n l a h a r t e r b e s a r

d i p e r k i r a k a n m e n g i k u t i K a l i P r o g o d i b a g i a n b a r a t .

E n d a p a n l a h a r t u a d i K a l i P r o g o , y a n g d i d u g a

b e r h u b u n g a n d e n g a n e n d a p a n l o n g s o r a n G u n u n g a p i

M e r a p i , t e r s i n g k a p d i G u n u n g S e n t o n o , d i t e p i b a r a t

j e m b a t a n K l a n g o n , k o o r d i n a t 0 7 ° 3 8

,

3 2 , 5 " L S -

1 1 0 ° 1 5 ' 1 5 , 8 " B T

( G a m b a r

1 4

b a w a h ) . K e t e b a l a n

s i n g k a p a n e n d a p a n l a h a r p a d a l o k a s i i n i l e b i h d a r i 2 0

m . F r a g m e n l a h a r b e r u k u r a n b u t i r r a t a - r a t a 3 0 - 5 0

c m , m a k s i m u m

1 5 0 c m ,

b e r b e n t u k m e r u n c i n g

-

m e m b u n d a r t a n g g u n g , t e r t a n a m d i d a l a m m a t r i k s t u f

k e r i k i l a n

b e r w a r n a p u t i h . F r a g m e n l a h a r i t u

b e r s t r u k t u r p e j a l - b e r l u b a n g , b e r k o m p o s i s i a n d e s i t

d e n g a n b e r b a g a i r a g a m t e k s t u r m u l a i d a r i a f a n i t

s a m p a i d e n g a n p o r f i r i , f e n o k r i s t e r d i r i a t a s p l a g i o k l a s ,

p i r o k s e n d a n h o r n b l e n d a y a n g t e r t a n a m d i d a l a m

m a s s a d a s a r a f a n i t .


14/18

1 7 8

J . G . S . M . V o l . 1 5 N o . 4 N o v e m b e r

20)4

h a l .

1 6 5 - 1 8 3

Pembahasan

B e r d a s a r k a n p a d a h a s i l p e n e l i t i a n

d i lapangan

b a t u a n p i r o k l a s t i k a T e r s i e r d i d a e r a h G o d e a n d a n

s e k i t a r n y a , y a n g b e r u p a b a t u l a p i l i p u m i s d a n t u f

t e l a h

d i t e r o b o s o l e h b a t u a n b e k u a n d e s i t p o r f i r i -

d i o r i t m i k r o . S e m a k i n d e k a t d e n g a n t u b u h b a t u a n

t e r o b o s a n

batuan

p i r o k l a s t i k a t e r s e b u t s e m a k i n k u a t

m e n g a l a m i u b a h a n h i d r o t e r m a l m e n j a d i t u f t e r s i l i k a ,

t e m p u n g p u t i f v k e l a b u ( k a o l i n - a r g i l i k ) , s e r t a l i m o n i t ,

S e k i l a s ,

t u f t e r s i l i k a p e n a m p a k a n n y a m i r i p d e n g a n

b a t u p a s i r s i l i k a a t a u k u a r s a . Sela)n d i t e r o b o s ,

s e b a g i a n b a t u a n p i r o k l a s t i k a a d a y a n g m a s u k

( t e r m a k a n )

k e dalam batuan

t e r o b o s a n s e h i n g g a

m e n j a d i x e n o l i t , d a n s e b a g i a n l a g i m e n j a d i b a t u a n

a t a p

(roofpendant)

d i a t a s b a t u a n t e r o b o s a n . B a t u a n

p i r o k l a s t i k a y a n g m e n j a d i x e n o l i t d a n b a t u a n a t a p

t e r s e b u t j u g a t e r u b a h d a l a m b e r b a g a i t i n g k a t a n . O l e h

s e b a b

i t u p e t a g e o l o g i l e m b a r Y o g y a k a r t a ( R a h a r d j o

d r r . , 2 0 1 2 ) d i s a r a n k a n u n t u k d i p e r b a i k i k e m b a l i .

D i d a e r a h G o d e a n d a n s e k i t a r n y a b a t u a n p i r o k l a s t i k a

b e r u p a b a t u l a p i l i p u m i s , t e r k a d a n g b e r c a m p u r

f r a g m e n l i t i k m e r u n c i n g ,

d a n t u f

m e m p u n y a i

k e t e b a t a n t e r s i n g k a p l e b i h d a r i 3 0 m. Batuan

p i r o k l a s t i k a k a y a p u m i s d a n s a n g a t t e b a l i t u b i a s a n y a

d i h a s i l k a n o l e h l e t u s a n k a l d e r a gunung a p i atau

t a h a p p e n g h a n c u r a n (destruction period) k e r u c u t

k o m p o s i t , y a n g t e r b e n t u k s e b e l u m n y a y a k n i p a d a

t a h a p p e m b a n g u n a n (construction period).

B a t u l a p i l i p u m i s y a n g t e b a l

(iebih

d a r i 2 0 m ) d a n

m a s i f d i p a n d a n g s e b a g a i i g n i m b r i t a t a u a l i r a n p u m i s

(pumice flows), s e d a n g k a n p e r s e l i n g a n b a t u l a p i l i

p u m i s

dengan t u f

d i p e r k i r a k a n s e b a g a i p r o d u k

l e t u s a n

T i p s P l i n i (Piin ian type ashfall s) yang

b e r l a n g s u n g b e b e r a p a t a h a p . B e r h u b u n g y a n g

t e r s i n g k a p

d i

p e r m u k a a n h a n y a b a t u a n p i r o k l a s t i k a

h a s i l t a h a p penghancuran dan t u b u h b a t u a n

t e r o b o s a n s e m i g u n u n g a p i , m a k a b a t u a n h a s i l t a h a p

p e m b a n g u n a n k e r u c u t k o m p o s i t s e b e l u m n y a

d i p e r k i r a k a n s u d a h h a b i s t e r e r o s i a t a u s e b a g i a n

m a s i h b e r a d a d i

bawah

p e r m u k a a n . D i P e g u n u n g a n

S e l a t a n

Y o g y a k a r t a - J a w a T e n g a h d a n

P e g u n u n g a n

K u l o n p r o g o Y o g y a k a r t a , b a i k b a t u a n h a s i l e r u p s i

p a d a t a h a p p e m b a n g u n a n m a u p u n t a h a p

p e n g h a n c u r a n , d a n b a t u a n t e r o b o s a n s e m i g u n u n g

a p i p u r b a m a s i h c u k u p l e n g k a p t e r s i n g k a p d i

p e r m u k a a n ( B r o n t o , 2 0 1 3 ) .

H a l i n i

m e n u n j u k k a n

b a h w a b a t u a n k e r u c u t k o m p o s i t G u n u n g a p i p u r b a

G o d e a n j a u h l e b i h t u a d a r i p a d a y a n g a d a d i k e d u a

p e g u n u n g a n b a t u a n g u n u n g a p i

T e r s i e r

t e r s e b u t

d i

a t a s . K e m u n g k i n a n l a i n k a r e n a G u n u n g a p i p u r b a

G o d e a n t e r l e t a k d i d a l a m g r a b e n B a n t u l - Y o g y a k a r t a

( B a r i a n t o , 2 0 0 9 ) , t u b u h b a t u a n k e r u c u t k o m p o s i t n y a

m e n g a l a m i p e n u r u n a n s e b a g a i a k i b a t k e g i a t a n

t e k t o n i k d i

d a e r a h i t u .

D a r i u r a i a n d i a t a s d i k e t a h u i b a h w a g e r a k a n

l o n g s o r a n G . M e r a p i m e m b e n t u r p e r b u k i t a n batuan

Tersier

G u n u n g

a p i

p u r b a

G o d e a n

s e h i n g g a

e n d a p a n n y a t e r t a h a n d a n t e r a w e t k a n c u k u p b a i k d i

bagian

utara.

D i

d a l a m e n d a p a n m a s i h d i j u m p a i

p e r l a p i s a n e n d a p a n s e b e l u m l o n g s o r , y a k n i e n d a p a n

p i r o k l a s t i k a ,

a l i r a n l a v a d a n e n d a p a n r o m b a k a n .

S e b a g a i a k i b a t p e r g e r a k a n l o n g s o r a n p e r l a p i s a n

e n d a p a n t e r s e b u t m e n g a l a m i f r a k t u r a s i s a n g a t k u a t ,

t e r b e n t u k r e k a h a n g e r g a j i d a n s e s a r k e c i l (minor).

C i r i - c i r i t e r s e b u t m e n u n j u k k a n b a h w a e n d a p a n

l o n g s o r a n G . M e r a p i d i G o d e a n t e r m a s u k f a s i e s

b o n g k a h (block

phases

atau

block

fades; U i , 1 9 8 3 ;

G l i c k e n , 1 9 8 6 ;

U i ,

1 9 9 7 ; N a k a m u r a d a n

Glicken,

1 9 9 7 ) . F a s i e s b o n g k a h e n d a p a n l o n g s o r a n i t u

d i y a k i n i b a h w a g e r a k a n l o n g s o r a n l e b i h b e r s i f a t

a l i r a n g r a v i t a s i l a m i n e r ; tidak turbulen s e p e r t i a l i r a n

p i r o k l a s t i k a .

P a d a s a a t t e r j a d i l o n g s o r a n t e m p e r a t u r

m a t e r i a l

j u g a d i n g i n , j a u h l e b i h d 'm g in d i b a n d i n g

t e m p e r a t u r a l i r a n p i r o k l a s t i k a . P e n e m u a n e n d a p a n

l o n g s o r a n G . M e r a p i d i

daerah

G o d e a n i n i

m e n u n j u k k a n b a h w a p a d a m a s a

l a l u

t e l a h t e r j a d i

l o n g s o r a n s a n g a t b e s a r t u b u h G . M e r a p i k e a r a h

b a r a t d a y a ( b a r a t

d a n

s e l a t a n ) m e l a n d a w i l a y a h

K a b u p a t e n M a g e l a n g J a w a T e n g a h k e m u d i a n

K a b u p a t e n S l e m a n Y o g y a k a r t a , s a m p a i j a r a k 3 0 - 3 5

k m d a r i p u n c a k M e r a p i ( G a m b a r 1 5 ) . D e n g a n a s u m s i

k e t e b a l a n r a t a - r a t a e n d a p a n l o n g s o r a n G . M e r a p i 3 0

m

d a n m e n u t u p i d a e r a h d a r i a l i r a n Kali Bedog

s a m p a i t e p i

t imur

P e g u n u n g a n K u l o n P r o g o ( K a l i

P r o g o ) s e l e b a r 1 0 k m , m a k a d i p e r k i r a k a n v o l u m e

e n d a p a n l o n g s o r a n i t u l e b i h d a r i 1 0 k m 3 . D e m i k i a n

b e s a r v o l u m e e n d a p a n d a n d a e r a h y a n g t e r d a m p a k

s a n g a t l u a s {lebih dan 3 0 0 k m 2 ) , m a k a e n d a p a n

l o n g s o r a n i n i t e r g o l o n g e n d a p a n l o n g s o r a n r a k s a s a

g u n u n g a p i .

B e r d a s a r k a n f a k t o r

p e n y e b a b

l o n g s o r a n Siebert

drr.

( 1 9 8 7 )

m e m b a g i l o n g s o r a n g u n u n g a p i m e n j a d i 2

t i p e ,

y a i t u

T t p e

B e z y m i a n n y d a n

T i p e

B a n d a i .

T i p e

p e r t a m a d i s e b a b k a n o l e h e r u p s i m a g m a p a d a w a k t u

l e t u s a n g u n u n g a p i , s e d a n g k a n T i p e B a n d a i

d i a k i b a t k a n o l e h

letusan

f r e a t i k ( h i d r o t e r m a l ) a t a u

t i d a k b e r h u b u n g a n d e n g a n k e g i a t a n g u n u n g a p i .

U n t u k l o n g s o r a n G . M e r a p i b e l u m d a p a t d i m a s u k k a n

k e d a l a m s a l a h s a t u t i p e l o n g s o r a n t e r s e b u t

d i

a t a s

k a r e n a b e l u m d i t e m u k a n e n d a p a n p i r o k l a s t i k a

p e n y e r t a

( T i p e Bezymianny)

a t a u m a t e r i a l u b a h a n

h i d r o t e r m a l s e b a g a i p e n c i r i a k i b a t l e t u s a n f r e a t i k .


15/18


Y o g y a k a r t a -

J a w a

T e n g a h

1 7 9

*

/

\

KAB SLEMAN

VOGlfAKARTA

^ ~ 1 E » w i l « ? ' I ^

; / I ,

U

i

1 3

s

k m

„

Aral

W I T H pnwiHi

G a m b a r 1 5 P e t a a r a h a l i r a n g r a v i t a s i l o n g s o r a n b a t u a n G. M e r a p i m e l a l u i d a e r a h

K a b u p a t e n M a g e l a n g , J a w a Te n g a h, m c n e r u s

ke

d a e r a h K a b u p a t e n

S l e m a n ,

Yo g y a k a r ta . E n d a p a n l o n g s o r a n

i t u

m e n g a l a m i r o m b a k a n

m e n j a d i a l i r an l a ha r , y a n g m e l a n d a d a e r a h K a b u p a t e n B a n t u l , d a n t e p i

t i m u r

K a b u p a t e n K u l o n Pr o g o , D a e r ah Is t i m e w a Y o g y a k a rt a .

J i k a

k e d u a n y a m e m a n g t i d a k a d a , m a k a l o n g s o r a n

G .

M e r a p i d a p a t d i p i c u o l e h k e g i a t a n t e k t o n i k . P e r i s t i w a

i t u b u k a n

h a l

y a n g t i d a k m u n g k i n , k a r e n a s e c a a r a

u m u m g u n u n g a p i i n i t e r l e t a k d i j a l u r t e k t o n i k a k t i f

P u l a u

J a w a , d a n

s e c a r a

k h u s u s b e r a d a d i d a l a m

g r a b e n

B a n t u l - Y o g y a k a r t a . D i J e p a n g , p a d a

2 1

M e i

1 7 9 2 G .

M a y u y a m a

d i

k a w a s a n

G . U n z e n

l o n g s o r

d i p i c u o l e h

g e m p a

b u m i t e k t o n i k

d a n

t i d a k

b e r h u b u n g a n d e n g a n k e g i a t a n v u l k a n i s m e s e t e m p a t

( N a k a m u r a d a n G l i c k e n ,

1 9 9 7 ) .

M e n g a c u p e n d a p a t U i d r r . , ( 1 9 8 6 ) d a n d e n g a n

m e m p e r t i m b a n g k a n k e t i n g g i a n p u n c a k

G .

M e r a p i

( +

2 9 0 0 m )

s e r t a d a t a r a n

G o d e a n Y o g y a k a r t a ( + 1 0 0

m ) , s e b a g a i l a n d a s a n l o n g s o r a n t e g a k

(vertical

collapse), d a n

v o l u m e e n d a p a n m e n c a p a i

1 0

k m 3 ,

s e h a r u s n y a j a r a k l u n c u r b a h a n l o n g s o r a n d a p a t

m e n c a p a i 5 0 - 1 0 0 k m d a r i s u m b e r . N a m u n

j i k a

b e n a r

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