Metamorphic Metamorphic RocksRocks

A. Vocabulary

1. Parent rock: Preexisting rock2. Recrystallization: A process in which rocks undergo change without truly melting

B. Key B. Key Ideas:Ideas:

1. Formed when existing rocks (igneous, sedimentary or metamorphic) are changed by HEAT AND/OR PRESSUREHEAT AND/OR PRESSURE2. The new rocks may resemble the “parent” rock in their mineral composition/color3. IMPORTANT- THE ORIGINAL ROCK CANNOT MELTCANNOT 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 C. The 2 Types of MetamorphismMetamorphism

1. REGIONAL: 1. REGIONAL: Large areas of rock are changed by HEAT & PRESSURE

Metamorphic mountains Metamorphic mountains formed from regional formed from regional

metamorphismmetamorphism

2. CONTACT: 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 Alaska’s Copper Mountain – contact metamorphismmetamorphism

D. the bells & whistles for D. the bells & whistles for metamorphic rock metamorphic rock

identificationidentification1. BANDING1. BANDING – alternating layers of different colored minerals due to different colored minerals due to sorting by densitysorting by density

a. These bands are usually distorted from the heat & pressureb. not to be confused with sedimentary layers (stratification)!!!

Stratification vs. Banding

Stratification (sed) vs. Banding (metamorphic)

FOLIATIONFOLIATION

2. FOLIATION2. FOLIATION – mineral alignmentmineral alignment – the minerals in the rock are layered, which causes breakages to often occur along flat surfaces- look for “scratches” in the rocks

Foliation – note the Foliation – note the “scratches” in the “scratches” in the

rock – this is mineral rock – this is mineral alignment!alignment!

More More foliatiofoliatio

n – n – slate & slate & phyllitephyllite

Banding – mica Banding – mica schistschist

ExcellenExcellent t

example example of of

banding banding & &

distortiodistortion – this n – this

is is GNEISS GNEISS

More More GNEISS GNEISS

E. Difference Between Marble and Quartzite

a. Both are white in colorb. 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

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

The GNEISS The GNEISS SONGSONG

OkayOkay……

Let’s sum Let’s sum up!up!

There are 3 classifications of There are 3 classifications of ROCKSROCKS

• IgneousIgneous – formed by the cooling of magma (melted rock)

• SedimentarySedimentary – formed by compaction & cementation of rock fragments

• MetamorphicMetamorphic – formed by heat & pressure changing existing rocks

Remember the “bells & Remember the “bells & whistles” when identifying whistles” when identifying

rocks!rocks!

• IgneousIgneous – obvious crystals of – obvious crystals of different mineralsdifferent minerals

• SedimentarySedimentary – stratification, – stratification, fragments, fossilsfragments, fossils

• MetamorphicMetamorphic – foliation, – foliation, bandingbanding