Información sobre las fuentes de abastecimiento

The construction o f volcanic edifices is due to an accumulation o f erupted

material over time. The complexity o f each volcanic structure governs the location and

frequency o f eruption, whether through a central vent or from points on the flanks.

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ind i c a t i ve o f ar eas w h e r e the crust is u nd er e xt en si on a l stresses. Rift z o n e s p r e s ent a l o n g t he s u m m i t s o f v o l c a n o e s ar e the s u r f a c e e x p r e s s i o n s o f d y k e s w a r m s (as d i s c u s s e d a b o v e ) and ar e re la t ed to the s h ap e and si ze o f t he v o l c a n o a nd the local te c t oni c re gi me . Sites o f e r upti on a w a y from the m a i n vent , l o we r d o w n on the flanks ar e t e r m e d flank, p a r as iti c or satellit e ve n t s a nd a r e c o m m o n l y s e e n on t errestrial v o l c a n o e s (e.g. D o w n i e and Wi lk i ns on , 1972; Fiske a nd J a c k s o n , 1972; C h e s t e r et al., 1985; F r a n c is , 1993) ( F i g u r e 2.7). E r u p t i o n s f r o m t h e s e v e n t s ar e fed by d y k e s r a dia ting out from the m a g m a reservoir. Fo ll owi ng a st udy o f S ap as M on s , Ke ddie and H e a d ( 1 9 9 4 b ) c o n c l u d e d that ve nt s located on the f l anks o f ‘t y p i c a l ’ large v en u si an v o l c a n o e s do not s h o w signi ficant associated lava flows. S tudi es by Brian et al. (2000; see C h a p t e r s 6 and 7) h o w e v e r s h o w e d t hat m a n y v e n u s i a n v o l c a n o e s d i s p l a y large n u m b e r s o f edifices on their flanks and m a n y exhi bit vent s with a s s oc ia te d lava flows. O n Earth flank vent s ca n o c c u r due to g r avit ati onal d e f o r m a t i o n o f t he m ai n edifice u n d e r its o w n w e i g h t ( F i ske and J ac ks on, 1972). P ro g r e ss i ve s a g g i n g o f the relat ively thin l i t ho sp h er e as v e n us i an edi fi ce g r o w to l arge v o l u m e s ( M c G o v e r n a nd Sol oma n,

1997) m a y pr o vi de a similar m e c h a n i s m for fissure dilation.

S u m m it eruption

r Flank eruption

7 P arasitic eruption

Fi gu r e 2.7. T e r m s c o m m o n l y used in d e s c r i b in g the sites o f e r u p t i o n s relative to a s i m p l e co ni ca l vol ca n o . F la nk e r up t i o ns c o m m o n l y c o m m e n c e wi th s u m m i t activity, but a c ti v i t y shifts to l o w e r levels w h e r e m o s t lava e m e r g e s . ‘ L a t e r a l ’ e r u p ti o n s are si mi l ar but m a y i nvol ve onl y mi ni mal s u m m i t activity. ( Af t e r Francis, 1993)

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