Transcript Igneous Rocks

GEOLOGISTS RECOGNIZE
THREE TYPES OF ROCKS
1) Igneous – rocks that cool from a molten state.
2) Sedimentary – rocks that form from the
eroded and weathered particles of pre-existing
rocks, a “re-cycled rock”.
3) Metamorphic – rocks that form by the
alteration of pre-existing rocks through heat
and pressure.
1) IGNEOUS ROCKS
2 Types:
a) Extrusive – Cool
quickly at or near the
surface. Small
crystals, fine texture.
b) Intrusive – Cool
Slowly beneath the
ground. Large
crystals, coarse
texture.
Igneous Rock Classification
High
Vesicular
Glassy
Pumice
Amount of Quartz
XXX
Obsidian
Low
Scoria
Geology Dept. Death Valley – Grand Canyon Field Trip:
A)IGNEOUS ROCK BODIES
• IGNEOUS ROCKS COOL FROM A MOLTEN STATE
• MOLTEN ROCKS ARE CALLED MAGMA
• DEEP WITHIN THE EARTH HEAT AND PRESSURE
CAUSE ROCKS TO MELT
• MAGMA IS A COMBINATION OF MOLTEN ROCK
AND THE DISSOLVED GASES IT CONTAINS
• WHAT HAPPENS WHEN MAGMA COOLS?
INTRUSIVE
IGNEOUS
ROCK
BODIES
1) Intrusive Igneous Rock Bodies:
a) Smaller Bodies – Sills, Dikes & Laccoliths
Dike
Sill
DIKE : CROSS-CUTS HOST ROCK
SILL: PARALLEL TO HOST ROCK
1) Intrusive Igneous Rock Bodies:
b) Large Bodies – Plutons & Batholiths
SIZE OF BATHOLITHS
UNDERSTANDING
CRYSTALLIZATION
1) Precipitation from
a saturated solution
UNDERSTANDING CRYSTALLIZATION
2) Crystallizing from a cooling melt
BOWEN’S REACTION SERIES
Temperatures at which silicate minerals
crystallize out of a cooling melt
1200o
600o
MAGMA BODIES ARE
HETEROGENEOUS:
THEY HAVE MANY
DIFFERENT SOURCES
AND CREATE MANY
DIFFERENT KINDS OF
ROCKS.
B) EXTRUSIVE IGNEOUS ROCKS: VOLCANOES