Earth Science
Chapter 4
Rocks!
Bellwork
• What is the most
interesting thing you
learned during your
research?
• Write it down and then we
will talk about it!
Classifying Rocks
• Rocks are classified using
• 1. mineral composition
• 2. color
• 3. texture
Mineral Content
• Rocks can be made of one, or a
combination of several
minerals
• There are about 20 main rockbuilding minerals
One mineral
Several minerals
Color
• Can help identify rocks
• Granite is usually light
• Basalt is usually dark
Granite/Basalt
Texture
Texture
Grain size
Grain
shape
Grain
pattern
Grain size
• Fine-some only seen with
microscope
• Coarse-easily seen without
microscope
• No visible grain-none seen
even with microscope
Grain pattern
• Bands
• Swirls
• Colored bands
• Random
Banded
Swirl
Colored bands
Random
Bellwork
• What did you find most
interesting about the crystal
presentations?
Igneous Formation
•Igneous: forms from the
cooling of magma or
lava
Igneous formation
Sedimentary formation
• Sedimentary rocks form
when particles of other
rocks or plant/animal
remains are presses and
cemented together
Sedimentary formation
Metamorphic formation
• Metamorphic formation:
forms when an existing
rock is changed by heat,
pressure, or chemical
reactions.
Metamorphic formation
You do it!
• Read section 2 about igneous rocks.
• Create a classification chart describing how
igneous rocks are classified
• Your chart should include information on
origin, texture, and mineral composition of
igneous rocks
• Charts should also include illustrations, all
vocabulary words, and examples of igneous
rocks
Igneous Rock
Classification
Origin
On or beneath
Earth’s surface
Texture
Depends on the size
and shape of
mineral crystals
Mineral composition
Dependent upon the
amount of silica in
the lava or magma
Origin
• Extrusive Rock: igneous rock
formed from lava that erupted
onto Earth’s surface
• Most common type is basalt
• Makes up most of the ocean’s
floors
Basalt
Origin
• Intrusive Rock: igneous rock
that formed when magma
hardened beneath the Earth’s
surface
• Most abundant intrusive rock
is granite
Texture
• Rapid cooling=small crystals,
fine grain
• Slow cooling=large crystals,
coarse grain
• Extrusive=smooth, fine grain
• Intrusive=coarse, large grain
Texture
Extrusive
Intrusive
Mineral Composition
• Lava is low in silica and dark
colored
• Magma is high in silica and
generally light colored
• Geologists look at rocks under a
microscope to determine the
mineral makeup
BELLWORK
•WHAT DID YOU FIND
MOST INTERESTING
ABOUT IGNEOUS ROCK
FORMATION?
SEDIMENTARY ROCKS
• READ SECTION 3 WITH A PARTNER
• MAKE A FLOW CHART DESCRIBING THE
FORMATION OF SEDIMENTARY ROCKS
• YOUR CHART SHOULD INCLUDE:
– DEFINITION OF SEDIMENT
– 4 STEPS OF THE PROCESS INCLUDING
EXPLANATION
– ILLUSTRATIONS
Sedimentary process
Erosion
Deposition
Compaction
Cementation
Erosion
•Natural forces break
down and carry small
pieces of rock
Erosion
Deposition
•The natural processes
eventually drop the
eroded rock/sediment
and they form layers
Compaction
• This presses the visible
layers of sediment together
Cementation
• During compaction,
minerals dissolve in water,
fill in gaps in the sediment,
and act as a glue holding
the newborn rock together
Cementation
CLASSIFY TYPES OF SEDIMENTARY
ROCKS
• MAKE A CLASSIFICATION CHART DESCRIBING
THE THREE MAIN TYPES OF SEDIMENTARY
ROCKS
• CHARTS SHOULD INCLUDE DESCRIPTION OF
ALL THREE TYPES
• HOW THEY FORM
• EXAMPLES
• ILLUSTRATIONS
Classifying Sedimentary Rocks
Sedimentary
rocks
Clastic
Organic
Chemical
Clastic
• Formed from rock fragments
being squeezed together
• They can be small or large rock
fragments
–Clay/pebbles
Clastic
• Most common are shale,
sandstone, conglomerate, and
breccia
• Most form from sand on
beaches, ocean floor,
riverbeds, and sand dunes
Shale
Sandstone