Metamorphic Rocks - Red Hook Central Schools

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Transcript Metamorphic Rocks - Red Hook Central Schools

Metamorphic
Rocks
A. Vocabulary
1. Parent rock: Preexisting
rock
2. Recrystallization: A
process in which rocks
undergo change without truly
melting
B. Key Ideas:
1. Formed when existing rocks
(igneous, sedimentary or
metamorphic) are changed by HEAT
AND/OR PRESSURE
2. The new rocks may resemble the
“parent” rock in their mineral
composition/color
3. IMPORTANT- THE ORIGINAL ROCK
CANNOT MELT WHEN IT BECOMES
METAMORPHIC! (If it melts and
solidifies, it’s igneous!)
Activity- Listen closely to
directions!
• 1. Send one group member to the front to
pick up the playdough
• 2. Carefully stack playdough slabs on top of
each other without blending them in any
way.
• A. Of the rock types we have talked about
already, which type forms like this?
• 3. Now, fold the playdough layers in half and
push down
• 4. What are some observations?
Animation of Metamorphism
• Metamorphism
C. The 2 Types of
Metamorphism
1. REGIONAL:
Large areas of
rock are changed
by HEAT &
PRESSURE
Metamorphic mountains formed
from regional metamorphism
2. CONTACT: Magma
touches layers of rock and
the HEAT causes the rock
layers to change
a. Little to no pressure is
involved with contact
metamorphism
(Contact
Touch)
“Liquid hot
magma!”
Alaska’s Copper Mountain – contact metamorphism
D. the bells & whistles for
metamorphic rock
identification
1. BANDING – alternating layers of
different colored minerals due to
sorting by density
a. These bands are usually
distorted from the heat & pressure
b. not to be confused with
sedimentary layers (stratification)!!!
Stratification vs. Banding
Stratification (sed) vs.
Banding (metamorphic)
FOLIATION
2. FOLIATION – mineral alignment – the
minerals in the rock are layered, which
causes breakages to often occur along flat
surfaces- look for “scratches” in the rocks
More
foliation
– slate &
phyllite
Foliation – note the
“scratches” in the rock –
this is mineral alignment!
Banding – mica
schist
Excellent
example
of
banding &
distortion
– this is
GNEISS

More
GNEISS

E. Difference Between
Marble and Quartzite
a. Both are white in color
b. Marble reacts with HCl (hydrochloric
acid) and quartzite does not because
marble is composed of recrystallized
Calcite
Remember… MORPHING is
all about CHANGE!
• Animoto Video
When I was young, liquid granite
I was diagnosed schizophrenic
Neither feldspar, nor mica, nor quartz
But the sum of the three
Bonded igneously
That means melted together for life
Well, I was hot and dejected
Oh, I was injected
Under layers and layers of dirt
But, it was there that I changed
All my crystals rearranged
Into G-N-E-I-S-S, gneiss
So, take a look, and you'll see
That I'm not what I used to be
I've been touched metamorphically
All the heat and the pressure
Have changed me forever
So don't take me for granite, I'm gneiss
The GNEISS
SONG
Well, I wasn't to been seen
Until time changed the scene
Exposing my face to the sun
But, now its here that I sit
Being worn down bit by bit
Oh, erosion is wearing me down
Refrain
So, be aware, have a look
Underground or underfoot
For that beautiful pinky-gray face
The Canadian shield
Holds a magnamous yield
Of the rock that was changed into
gneiss
Refrain
Okay…
Let’s sum up!
There are 3 classifications of
ROCKS
• Igneous – formed by the cooling of
magma (melted rock)
• Sedimentary – formed by
compaction & cementation of rock
fragments
• Metamorphic – formed by heat &
pressure changing existing rocks
Remember the “bells & whistles”
when identifying rocks!
• Igneous – obvious crystals of
different minerals
• Sedimentary – stratification,
fragments, fossils
• Metamorphic – foliation, banding