Download Earth Science U1C3L1 - secondary

Earth Science
Unit 1
Chapter 3
Lesson 1
Igneous Rocks
Types of Rocks
 Rock-
A hard substance composed of
one or more minerals
– Rocks can be organized by the way they
form
– Three types of rocks: Igneous,
metamorphic, sedimentary
Igneous Rocks
 Defined:
rocks formed by cooled and
hardened magma or lava
– Magma- melted rocks beneath the
Earth’s surface
– Lava- Magma when it reaches the
Earth’s surface
 Composed
of melted rock, water vapor,
carbon dioxide, and rock crystals
Classifications
 Felsic
Rocks-Lightweight, lightcolored, igneous rocks
– They are rich in silicon, aluminum,
sodium, and potassium
– They form from minerals that are acidic
– Granite is an example
Classifications
 Mafic
Rock- Dark colored, heavy
igneous rocks
– Rich in iron, magnesium, and calcium
– They form from minerals that are
alkaline (bases)
– Example: Basalt
Other Classifications
 Texture
 Size
 Shape
 Arrangement
 Distribution
of minerals
Intrusive Rocks
 Igneous
rocks that form when
magma cools beneath the Earth’s
surface
– If they cool quickly they form fine grain
crystals that can’t be seen with the
naked eyes
– If they cool slowly, they form large
coarse grained crystals that can be seen
with the naked eye
Extrusive Rocks
 Formed
when lava cools above the
Earth’s surface
– Have finer crystals than intrusive rocks
– Example: cooled lava from volcanoes
Thought Questions
 How
are intrusive and extrusive
rocks formed?