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Volcanic eruptions can vary in violence depending on the composition, temperature, and dissolved gases of the magma. More viscous magmas, such as those with high silica content, have a more violent eruption as gases cannot escape as easily. Materials produced from eruptions include pyroclastic fragments like ash, dust, pumice, and lapilli. Different types of lava flows, such as basaltic pahoehoe lava and aa lava, are influenced by the magma viscosity and gas content. In general, volcanoes have a conduit that carries magma to the surface vent opening.

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45 views1 page

V

Volcanic eruptions can vary in violence depending on the composition, temperature, and dissolved gases of the magma. More viscous magmas, such as those with high silica content, have a more violent eruption as gases cannot escape as easily. Materials produced from eruptions include pyroclastic fragments like ash, dust, pumice, and lapilli. Different types of lava flows, such as basaltic pahoehoe lava and aa lava, are influenced by the magma viscosity and gas content. In general, volcanoes have a conduit that carries magma to the surface vent opening.

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el
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VOLCANIC ERUPTIONS MATERIALS ASSOCIATED WITH VOLCANIC

- Factors that determine the violence of an ERUPTIONS


eruption - Pyroclastic materials
o Composition of the magma o “Fire fragments”
o Temperature of the magma o Types of pyroclastic material
o Dissolved gases in the magma  Ash and dust – fine, glassy
- Viscosity of magma fragments
o Viscosity – a measure of a material’s
resistance to flow TYPES OF PYROCLASTIC MATERIAL
o Factors affecting viscosity - Pumice – from “frothy” lava
 Temperature (hotter magmas - Lapilli – “walnut” size
are less viscous) - Cinders – “pea-sized”
 Composition (silica content) - Particles larger than
 High silica – high
viscosity (e.g., rhyolitic
lava) VOLCANOES
 Low silica – more fluid - General features
(e.g., basaltic lava) o Conduit, or pipe, carries gas-rich
 Dissolved gases (volatiles) magma to the surface
 Mainly water vapor o Vent, the surface opening (connected
ang carbon dioxide to the magma
 Gases expand near the
surface
 Provide the force to
extrude lava
 Violence of an eruption
is related to how easily
gases escape from
magma
o Easy escape
from fluid
magma
o Viscous magma
produces a
more violent
eruption
o Lava flows
 Basaltic lavas are more fluid
 Basaltic lavas are more
fluid
 Types of lava:
o Pahoehoe lava
(resembles
braids in ropes)
o Aa lava (rough,
jagged, blocks)
 Gases
o One to five
percent of
magma by
weight
o Mainly water
vapor and
carbon dioxide

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