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Ch.5 & 8
Volcanos & Volcanism - Metamorphism & Metamorphic Rocks
28
Geology
Undergraduate 1
10/24/2012

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Term
Pyroclastic
Definition
Magma that erupts explosively.
Term
Felsic
Definition
SiO2 Content: 66-76%
Feldspar/Rhiolite
Silica Rich
Term
Intermediate
Definition
SiO2 Content: 52-66%
Diorite
Term
Mafic
Definition
SiO2 Content: 45-52%
Basalt/Gabbros
Iron Rich
Term
Ultra-Mafic
Definition
SiO2 Content: 38-45%
Peridotite
Mantle Rock
Term
Volcanic Gases
Definition
Gases(primarily water vapor) constitute only a small percent of magmas.
Term
Aa Lava
Definition
Angular fragments.
Pyroclastic
Term
Pahoehoe
Definition
Smooth surface
Term
Pillow Lavas
Definition
Interconnecting mass from underwater eruption of basaltic lavas
Term
Lava Tube Cave
Definition
Lava flow ceased & left a long cave-like channel
Term
Columnar Joints
Definition
Formed by cooling & contraction of lava, most common in basalt & andesite lava flow.
Term
Caldera
Definition
circular volcanic depression that forms when the summit of a volcano collapses into its magma chamber
Term
Shield
Definition
Non-explosive; Gentle Slope
Term
Cinder Cones
Definition
Cinder cone volcanoes consist of:
Cinder-like pyroclastic materials accumulated as small steep-sloped cones
Term
Composite (Strato) Volcanoes
Definition
Consist of layers of lava flows, pyroclastic debris, and volcanic mud flows(lahars).
Most Dangerous
Term
VEI
Definition
Volcanic Explosivity Index
Term
Metamorphism
Definition
Transformation of rocks without melting
Term
Shields
Definition
Oldest part of continental crust
Term
Principle Activities
Definition
Heat, Pressure, Fluid Activity
Term
Types of Pressure
Definition
Lithostatic & Differential
Term
Fluid Activity
Definition
Metamorphic Fluids include water vapor & cO2
Term
Contact Metamorphism
Definition
High Temperature & Low Presure
Aureoles (baked zones) occur around magmas
Term
Dynamic Metamorphism
Definition
Rocks are ground and crushed in faults
Term
Regional Metamorphism
Definition
Most common;Broad Range;
Temp & pressure act as driving forces
Term
Metamorphic Grade
Definition
Degree of metamorphic change a rock has undergone
Term
Index Minerals
Definition
Certain minerals are only known to form under specific ranges of metamorphic temp & pressure.
Term
Foliated Textures
Definition
Produced by preffered orientation of platy minerals due to pressure
(slate,schist, gneiss)
Term
Non-Foliated Textures
Definition
Randomly Oriented
Limestone->Marble, Quartz Sandstone->Quartzite
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