NOTE: The information in these handouts are
not my own but are from several references.
These handouts are made for reference to
points and not as a means to an end. Reading
from books and others references is still more
beneficial to learning.
What is a rock?
a naturally-occurring aggregate of one
or more minerals; may or may not
contain mineraloids, natural glass and
Types of rocks vary based on
composition, color, texture, structures,
The Rock Cycle
What are igneous rocks?
• Ignis = fire
• Formed from solidification of magma
(intrusive) or lava which flows out from
What is magma?
• Molten material which may contain
suspended crystals and dissolved
volatiles (gases e.g. water vapor, CO2,
• Composed of mobile ions of the 8 most
abundant elements in the Earth’s crust:
O, Si, Al, K, Ca, Na, Fe, Mg
• role of heat
• role of pressure
• role of volatiles
Sources of heat for melting in the crust
• Original heat
• Radioactive decay
ORIGIN AND FORMATION OF MAGMA
Magma forms at:
• Mid-Oceanic Ridges (MOR)
• Subduction Zones
Classification of Magma
Crystallizes at ~1000 1200ºC
Crystallizes at ~600ºC
VARIATION IN COMPOSITION OF MAGMA
- Any process that causes magma
composition to change
Assimilation of country rock
FORMING IGNEOUS ROCKS
Extrusive (volcanic) – molten rock formed at
Ex. Basalt, Andesite, Rhyolite...
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