Transcript Igneous Rocks - Earth Science

Physical
Geology
Igneous Rocks
Important Terminology
 Magma
 Molten
rock below
Earth’s surface
 Lava
 Molten
surface
rock at Earth’s
 Pyroclastics
 Solids
erupted at
Earth’s surface
Important Terminology

Extrusive
 Formed above Earth’s surface
 Also referred to as volcanic
 Made of small crystals that cooled rapidly
Important Terminology

Intrusive
 Formed below Earth’s surface
 Also referred to as plutonic
 Made of large crystals that cooled slowly
Classification
 Composition

Ultramafic
 Very

heavy, dark minerals
Mafic
 Heavy,

Intermediate
 Mixture

dark minerals (Fe and Mg)
of heavy and light minerals
Felsic
 Lighter
in color and density (K, Al,
and Na)
Classification
 Glassy
 Example:
 Exhibits
Conchoidal fracture
 Vesicular
 Bubbly
Obsidian
 Example: Pumice & Scoria
texture caused by escaping gas
Classification
 Crystalline
 Aphanitic
(fine grained crystals)
 Phaneritic (coarse grained crystals)
Basic Igneous Rocks Classification
Phaneritic
Felsic
Intermediate
Mafic
Ultramafic
Granite
Diorite
Gabbro
Peridotite
Komotite
Aphanetic
Ryolite
Andesite
Basalt
(Only formed in
Archean
(no current
examples!))
Glassy/
Vesicular
Obsidian
Pumice
Scoria
Felsic Rocks
 Ryolite
 Aphanetic,
Volcanic
Rock
 Lava Domes cause this
type of rock
 Very dangerous!
 Ex: Mount St. Helens’
lava dome
Felsic Rocks
 Granite



Phaneritic, Plutonic Rock
Magma chamber cools
and solidifies
Erosion reveals the rock
below
 Ex: Elephant Rocks
Intermediate Rocks
 Andesite


Aphanetic, Volcanic Rock
Composite
Cones/Stratovolcanoes
formed this type of rocks
 Andesitic
lava and
pyroclastic layers form this
volcano
 Ex: Mount Mayon and
Mount Shasta
Intermediate Rocks
 Diorite



Phaneritic, Plutonic Rock
Magma chamber cools
and solidifies
Erosion reveals the rock
below
 Ex:
France (St. Quay)
Mafic Rocks
 Basalt


Aphanetic, Volcanic Rock
Shield volcanoes cause this type of rock
 Very
low viscosity
 Ex: Mauna Loa
Mafic Rocks
 Gabbro



Phaneritic, Plutonic
Rock
Magma chamber
cools and solidifies
Erosion reveals the
rock below
 Ex:
Michigan Waterfall
Ultramafic Rocks
 Komotite


Aphanetic, Volcanic Rock
Mainly restricted to the Archean
age
 Andesitic
lava and pyroclastic
layers form this volcano
 Ex: Island of Gorgona on the
Caribbean Oceanic plate off the
Pacific coast of Colombia
Ultramafic Rocks
 Peridotite



Phaneritic, Plutonic Rock
Magma chamber near the
mantel cools and solidifies
Erosion reveals the rock below
 Ex:
Ocean Ridges where the
rock is forced upward