metamorphic metamorphic rocksrocks

ESRT page 7ESRT page 7

Key Key ideasideas

•Formed when existing rocks are changed by HEAT & PRESSURE, HEAT & PRESSURE, forming forming new, larger, denser crystalline new, larger, denser crystalline structuresstructures

•The new rocks resemble the “parent” rock

•Parent rock: Preexisting rock

•Recrystallization: A process in which rocks undergo change without truly melting

More Key Ideas• IMPORTANT- THE ORIGINAL

ROCK CANNOT MELTCANNOT MELT WHEN IT BECOMES METAMORPHIC! (If it melts, it’s igneous!)

• Metamorphism

Types of Types of metamorphismmetamorphism

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

Metamorphic mountains Metamorphic mountains formed from regional formed from regional

metamorphismmetamorphism

• CONTACTCONTACT

• Magma

touches

layers of rock

and the HEAT

causes the

rock layers to

change

Alaska’s Copper Mountain – contact Alaska’s Copper Mountain – contact metamorphismmetamorphism

the bells & whistles for the bells & whistles for metamorphic rock metamorphic rock

identificationidentification• BANDINGBANDING – alternating layers

of different colored minerals different colored minerals due to sorting by densitydue to sorting by density– These bands are usually

distorted from the heat & pressure

– not to be confused with sedimentary layers!!!!!!

Stratification (sed) vs. Banding (metamorphic)

Stratification vs. Banding

FOLIATIONFOLIATION• FOLIATIONFOLIATION – mineral alignmentmineral alignment – the

minerals in the rock are layered, which facilitates breakage along flat planes- 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

Difference Between Marble and Quartzite

-Both are white in color- Marble reacts with HCl acid and

quartzite does not

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 downRefrain 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, banding – foliation, banding