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Unformatted text preview: esult of enhanced runout over the sea.
It is proposed that the generation of steam at the
flow/seawater interface may have led to a reduction in the
sedimentation of particles and consequently a delay in the
time before the flows ceased lateral motion and became
buoyantly convective. The buoyant distal edge of these
ash-and steam-laden clouds lifted off into the atmosphere,
leading to cooling, condensation, and mud rain.” 10 Pyroclastic surges are Pyroclastic Surges dilute, high energy
pyroclastic density currents
that typically produce thin,
bedded and cross-bedded
to massive deposits. Pyroclastic surges are
commonly associated with
explosions, but may also be
associated with other
phenomena, such as dry
volcanic explosions and
pyroclastic flows. In reality, surges and flows
form a continuum - with
grain density and turbulent
energy main factors. Characteristics of Pyroclastic
Surge Deposits Partially topographically
constrained T h in o v e r h ills , th ic k e n in v a lle y s Sorting variable W e a k to g o o d V e r y c o a r s e c la s ts a n d b lo c k s o f
p y r o c la s tic flo w s g e n e r a lly la c k in g F in e s t fr a c tio n a ls o la c k in g N o t a s w e ll s o r te d a s fa ll d e p o s its Often show evidence of lateral
transport R ip p le s B a s a l s c o u r in g C r o s s b e d d in g Highly fragmented (generally
small grain size) 11 Generation of Surges B a s e S u rg e Explosive interaction of magma and water Eruptive colu...
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This document was uploaded on 03/04/2014 for the course EAS 458 at Cornell University (Engineering School).
- Fall '06