Ch.4 Igneous Rocks and Intrusive Igneous Activity Flashcards
Magma that reaches the surface
Lava
Molten rock material below the surface.
Magma
Material from the forceful eruption of magma into the atmosphere.
Pyroclastic Material
extrusive rocks cool and crystallize very quickly.
Volcanic
(intrusive) rocks cool and crystallize very slowly.
Plutonic
Silica rich; gooey and thick
>65% silica; abundant Na, K, Al.
Felsic
Silica poor; thin and runny
(52% - 45%) silica; abundant Ca, Fe, Mg.
Mafic
Compositions between felsic and mafic
(53% - 65%) Silica content
Intermediate
<45% Silica content
Ultra Mafic
A substance’s resistance to flow.
Temperature is a factor, but composition is a more important factor.
In lava and magmas the formation of silica tetrahedral networks controls this.
Viscosity
Extrusive; fine grained (small crystals), rapid cooling.
Aphanitic
Intrusive; coarse grained (large crystals), slow cooling.
Phaneritic
phenocrysts and groundmass, two stage cooling history.
Porphyritic
Fragment generated by explosive volcanism.
Pyroclastic
No crystal structure
Glassy
Gas cavities
Vesicular
Composed of volcanic ash
Tuff
Composed of volcanic glass.
Obsidian
Composed of volcanic glass, vesicular, ______ floats on water.
Scoria and Pumice
describes the sequence of mineral crystallization in a cooling magma.
Shows how mafic, intermediate and felsic magmas could derive from a single original parent mafic magma
Bowen’s Reaction Series
Contains only ferromagnesian silicates.
Discontinuous Branch
Contains only non ferromagnesian silicates.
Continuous Branch
country rock is consumed by magma
Assimilation
Crystals form and sink to the bottom
Crystal settling
When a mafic and felsic magma chamber mix to form an intermediate magma.
Magma Mixing
Cracks on the ocean floor where magma reaches the ocean waters.
Spreading Ridges
Melting of ocean sediments and Si rich continental crust.
Subduction Zones
A tabular or sheet like pluton that is concordant (parallel) with the rock layers.
Sill
A tabular or sheet like pluton that is discordant with the rock layers
Dike
A pluton with a mushroom like shape
Laccolith
The largest of the plutonic bodies (at least 100 km2)
Batholith
Smaller than batholith (less that 100 km2)
Stock
