10/5/2015
 Objectives
 Distinguish between texture and composition
 Describe the formation of igneous rocks
 Homework
 Rock Cycle Story – due Monday 10/5
 ADV – Article presentations Friday!
Warm Up
 Update ISN Table of Contents
 Using the information you learned yesterday, work
with your group to write a general definition of each
rock type on page 15 in your ISN
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Magma
 Melted rock
 Magma – in the ground
 Lava – above ground
 Forms in three ways
 When rock is heated
 When pressure is released
 When rock changes composition
 A change in any of these factors will affect
melting point
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Latin for “fire”
A. Formation  Cooled, solidified magma
B. Characteristics 
Different igneous rocks are characterized by their
texture and composition.
Same composition,
different texture.
Latin for “fire”
A. Formation  Cooled, solidified magma
B. Characteristics 
Different igneous rocks are characterized by their
texture and composition.
Same texture,
different composition.
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Coarse-grained
Fine-grained
Felsic
Mafic
Granite
Basalt
Felsic  Light colored, less dense;
Rich in aluminum, potassium, silicon
Mafic  Dark colored, more dense;
Rich in iron and magnesium;
low silicon content
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Fine-grained texture
Course-grained texture
Texture is related
directly to
Porphyritic texture cooling rate! Glassy texture
Both coarse
and fine grains
Extremely fine
Intrusive  Igneous rock formed
within the earth
Extrusive  Igneous rock formed at the
Intrusive
(slow cooling)
Texture  coarse
earth’s surface (from lava)
Both Intrusive
Extrusive
AND Extrusive
(slow…
then fast)
(fast cooling)
Texture  fine
Texture  porphyritic
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Formation When magma erupts or extrudes
onto Earth’s surface
Lava flow from:
• Volcano eruption
• Fissures – cracks in Earth’s crust
Cools quickly
Very small or no crystals
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Extrusive (air bubbles
form as magma rises
and gas escapes)
Texture  Fine, or vesicular
Extrusive (cools
too fast for
crystals to
form at all)
Texture  glassy
(extremely fine)
(with air bubbles)
Intrusion When magma cuts or pushes
through other rock layers and
solidifies into igneous rock
Volcanic neck
Dike
Sill
Batholith
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What does a rock’s texture tell you
about the composition?
NOTHING  remember, two
rocks can have similar
composition but completely
different texture.
The two characteristics are …
INDEPENDENT OF EACH OTHER!
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10/5/2015
1. What determines the texture of an igneous
rock?
2. Describe how each of the following textures
forms:
A.
B.
C.
D.
E.
Coarse
Fine
Porphyritic
Vesicular (bubbly)
Glassy
 Goals
 Distinguish between different types of rocks
 Describe the way rocks forms
 Identify characteristics of each type of rock
 Agenda
 Warm Up
 Sedimentary & Metamorphic Notes
 Formation of Rocks Review
 Homework
 Rock Cycle Story
 ADV – Article Presentations tomorrow
- Initial blog post due tomorrow
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10/5/2015
 Little pieces of rock (sediment) collect in one
area. As layer after layer settles, the weight on
the sediments increases and slowly “glues” the
pieces together into rock
 Formed by:
1. Weathering (breaking down of rock)
2. Erosion (movement of sediments)
3. Deposition (collection of sediments)
4. Compaction & Cementation
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 Breakdown of rock
 Mechanical or chemical
Frost Action
Moss
Root Action
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Acid rain
Oxidation
 Movement/wearing away of rock
 Gravity (Mass wasting)
 Wind
 Running water
 Glaciers
 Waves
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Soil creep
Slumping
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Niagara Falls
Yellowstone
Canyon & River
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 The laying down and collection of sediment
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Nile River
Delta
Lateral moraine
Cape Cod
(spit)
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(categorized by composition)
 Clastic Rocks (rock fragments)



Conglomerates (pebbles)
Sandstones (sand)
Shales (mud & clay)
 Chemical Rocks (evaporation)

Ex: rock salt, limestone, geodes, gypsum
 Organic Rocks (once living)

Ex: limestone(coral and shells), coal (plants)
Conglomerate
Shale
Sandstone
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Gypsum rock
Limestone
Geode
Coal (plant mateiral)
Limestone (shell & coral)
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A. Meaning  Meta = change
Morph = shape
B. Characteristics  Rocks that have been changed in
structure, texture, or composition
C. Forces  Heat, pressure, or chemical changes
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D. Under normal conditions, temperatures of over
1000° C would cause rock tomelt
_______.
E. Metamorphic rock may not melt, even at these
extreme temperatures because of…
PRESSURE
In other words, the millions of tons sitting
on top of the deep rock layers press the
rock together and won’t allow it to melt
into a liquid.
F. With all that pressure squeezing the rock,
mineral grains will squeeze
sometimes the ___________________
into parallel bands.
Make sure you
don’t confuse
banding and
stratification.
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Foliated
Mineral
bands
•
•
Nonfoliated
Force of
compression
Minerals are in
parallel alignment
Mineral bands are
perpendicular to the
compression force
•
•
Minerals become
recrystallized
Resembles a coarse
grained igneous rock
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•
•
•
When one rock undergoes extreme heat and
pressure, the elements that make it up may
combine to form different minerals.
•
When you look at a metamorphic rock, you know
that it is the altered, metamorphosed form of
parent rock
another rock, which is called the ______________.
Occurs around the edges of a hot magma chamber
Rocks closest to the igneous intrusion will exhibit
the biggest change in texture and composition
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•
•
Occurs due to plate movement or collision
Happens deep in the crust, over a large “region”
rather than a localized pocket of magma
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•
•
One metamorphic rock can undergo
more metamorphism to become
another metamorphic rock.
Foliation increases each time more
heat and pressure are applied.
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