Transcript Igneous rock

Igneous rocks
The Beginning
What is a rock?
Rocks are
solid materials
made of one
or more
minerals.
Common Igneous rockforming minerals
Olivine
Pyroxene
Amphibole
Feldspar
Mica
Quartz
Formations from molten
materials
Material from a volcano or deep
inside the earth cools to form
extrusive and intrusive rocks
What is Magma?
Magma is molten rock located
beneath the surface of the Earth
often collects in a magma chamber.
Magma is a complex hightemperature (between 650 and 1200
°C)
silicate solution that is ancestral to all
igneous rocks
Magma Continued
Magma has a lower density than the
surrounding rocks of the mantle.
Similar to a lava lamp
Less dense because of its composition.
Magma that reaches the earths surface
is called lava
Extrusive
Fine grained with small crystals
Magma that doesn’t reach earths
surface
Intrusive
 Coarse texture with large crystals
 Igneous rocks
 Granite
 Cools slowly
 Pumice, Obsidian,
Scoria
-cool quickly
- pumice and scoria
gas is steamed
out
Basaltic rocks
Basaltic (or
mafic) magma
has a high iron
and magnesium
content.
Associated with
Shield volcanoes
and and hot spots
Dark in color.
Intermediate rock
Andesitic magma
has a mixture of
iron, magnesium,
sodium, and silica
(SiO4).
Intermediate
between Basaltic
and Granitic
magma.
Granitic or Felsic Rock
Granitic rock
(rhyolitic magma)
has a high
concentration
of Silicon and
Aluminum.
Associated with
composite
volcanoes
light in color
Comparing Rocks U.S.G.S - J. Johnson
http://volcanoes.usgs.gov/Products/Pglossary/VolRo
cks.html#flow
Component of Igneous
Rocks from U.S.G.S
Shield Volcanoes
 Mauna Loa (top 2
pics) is the world’s
largest
 Basaltic eruptions
 Lava flows
 Not very explosive
 http://www.geology
.sdsu.edu/how_volca
noes_work/index.ht
ml
Lava falls, channels, solid
basalt, and lava tube
Composite or
Stratovolcanoes
 Composition varies
 Alternating basaltic
to rhyolitic lavas and
teprha (solids),
overall compostion is
andesitic
 Explosive Pinian
eruptions
 Abundant in Ring of
Fire along
subduction zones
 Mt. Fuji, Japan
shown right
Explosive Eruptions and
pyroclastic flows
Cinder Cone or Scoria
Cone Volcano
 Composed of basalt
tephra, occasionally
andesitic
 Most common,
smallest volcanoes
 Associated with
stombolian eruptions
- Mt Etna, Paracutin
Strombolian eruptions
Blasts of highly
vesiculated basalt
= scoria with lots
of holes
Pyroclastics or Tephra
Classified on the
basis of size
Ash - < 2mm
Lapilli - pea to
walnut sized
Blocks and bombs
How Volcanoes Work
For more information on
volcanoes:
http://www.geology.sdsu.edu/how
_volcanoes_work/index.html