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Igneous Structures and Field Relationships - Faculty web pages

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Figure 4-184<br />

18. Types of pyroclastic flow deposits.<br />

After MacDonald (1972), Volcanoes. . Prentice-Hall,<br />

Inc., Fisher <strong>and</strong> Schminke (1984), Pyroclastic<br />

Rocks. SpringerS<br />

pringer-Verlag. . Berlin.<br />

a. collapse of a vertical explosive or plinian column<br />

that falls back to earth, <strong>and</strong> continues to travel along<br />

the ground surface.<br />

b. Lateral blast, such as occurred at Mt. St. Helens<br />

in 1980.<br />

c. “Boiling-over” of a highly gas-charged magma<br />

from a vent.<br />

d. Gravitational collapse of a hot dome (Fig. 4-18d). 4

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