Page 148 - Fundamentals of Physical Volcanology

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PYROCLASTIC FALLS AND PYROCLASTIC DENSITY CURRENTS 125

Wilson, L. & Heslop, S.E. (1990) Clast sizes in terres- day and a fall deposit produced by the same
trial and martian ignimbrite lag deposits. J. Geophys. eruption conditions on a windy day?
Res. 95, 17,309–314. 3 A volcano 1000 m high with steep slopes has
Woods, A.W., Bursik, M.I. & Kurbatov, A.V. (1998) a volatile-poor eruption that ejects gas and
−1
The interaction of ash flows with ridges. Bull. pyroclasts at 100 m s . The erupted mixture col-
Volcanol. 60, 38–51. lapses down the side of the volcano to produce
a pyroclastic density current. What is the max-
imum speed of the current when it reaches the
8.7 Questions to think about foot of the volcano? Assume that the acceleration
−2
due to gravity is 10 m s .
1 If you were able to find only one exposure of 4 What do you think might happen to a pyroclastic
a fall deposit but knew the likely vent it came density current if it reaches a shore line and starts
from, what could you infer about the eruption? to flow over the water surface?
2 What should be the main difference between
a fall deposit produced by an eruption on a calm