Ch.4 Igneous Rocks Flashcards
Igneous Rocks
Formed by the “freezing” of a melt of materials (molten material)
Lava
molten material on the surface
Magma
Molten material inside of the earth
Extrusive/Plutonic
Fine-grained rocks that have been frozen above grown
Intrusive/Volcanic
Coarse grain rocks formed inside of the earth/below ground
Xenolith
a piece of rock trapped in another type of rock
Batholith
geographically large Magma chambers that have frozen
Pluton:
local magma chambers that have frozen; Can form into big mounds of igneous rock
Sill
horizontal igneous rock
Dike
vertical igneous rock
Felsic
Rocks or minerals with HIGH silica content. Will be lighter in colour.
Intermediate
Rocks or minerals with moderate amounts of silica content. Will be grey/an intermediate colour.
Mafic
Rock/minerals with LOW amounts of silica. These will be dark in colour
Ultramafic
rocks/minerals with very very low silica content. Will be the darkest in color.
How do we identify igneous rocks?
- Mineralogic composition
- Texture
Terms to describe texture of igneous rocks:
- Pegmatitic
- Phaneritic
- Aphanitic
- Glassy
-Porphyritic - Vesicular
-Amygdaloidal:
Pegmatitic
Very large crystals
Phaneritic
Large crystals
Aphanitic
Small crystals
Glassy
VERY Small Crystals
Porphyritic
a distinct difference in the size of the crystals
Vesicular
large holes from trapped gas
Amygdaloidal
Amygdaloids are simply vesicles that have been filled in with a secondary mineral long after the flow cooled
