Hampden-Wilbraham Regional District

TASA The Wonders of Rocks and Minerals
Metamorphic Rocks Script

Metamorphic Rocks are Changed Rocks

Recall from the discussion of the rock cycle that metamorphic rocks are changed rocks. “ Meta” means change and “morph” means form.

Where steep, rocky slopes occur the process of weathering may produce large quantities of rock fragments that pile up to produce talus slopes.

Metamorphic rocks can form from igneous rocks…. (Click replay to see Granite metamorphosed into Gneiss.)

…sedimentary rocks… Sample: slate

…or even from other metamorphic rocks... (Click replay to see Slate metamorphosed into Mica Schist.)

The word metamorphism means to ______ . Choose crystallize, change form, compact or weather. Click “is this right?”

 The igneous rock granite can become ______ through the metamorphic process. Choose slate, schist, gneiss, or marble. Click “is this right?”

The sedimentary rock shale can become _______ through the metamorphic process. Choose slate, quartzite, anthracite, or marble. Click “is this right?”

Even the metamorphic rock slate can become _____ through the metamorphic process. Choose slate, schist, quartzite, or marble. Click “is this right?”

 

What Causes Metamorphism?

The causes of metamorphism are heat, pressure, and chemically active fluids.

Perhaps the most important cause of metamorphism is heat. Rocks found near the surface of Earth may be subjected to intense heat when they are intruded by magma.

Here the layers of rock have been intruded by magma and “baked” by the molten rock.

When the sedimentary rock quartz sandstone changes, its quartz grains are fused together forming the metamorphic rock quartzite. (Click replay to see quartz sandstone metamorphosed into Quartzite.)

Another sedimentary rock, limestone, changes to form the metamorphic rock marble. Marble can be carved and polished, and is used by sculptors, and to decorate buildings. (Click replay to see limestone metamorphosed into Marble.)

 Rocks may also be changed when they are under great pressure (stress.) (Click replay to see rocks metamorphosed under pressure.)

When the igneous rock granite changes, some of its mineral grains are aligned, giving the resulting metamorphic rock gneiss a banded appearance. (Click replay to see Granite metamorphosed into Gneiss by pressure.)

Chemically active fluids, most commonly hot water containing dissolved materials, also cause rocks to change.

When the metamorphic rock slate is changed, its mineral composition is altered to form another metamorphic rock, garnet mica schist. (Click replay to see Slate metamorphosed into Garnet mica schist.)

 What causes metamorphism? Choose one: a. Heat b. Pressure c. chemically active fluids d. All of the above Click “Is this right?”

The most common chemically active fluid responsible for enhancing metamorphism is _____ . Choose liquid nitrogen, carbonic acid or water.

Which of these metamorphic rocks formed from the sedimentary rock quartz sandstone? Click on the correct answer. Slate (Slate formed from a sedimentary rock, but it was not sandstone. Try again.) or Quartzite (Correct, quartz sandstone changed to form quartzite. Quartzite is made of only one mineral, quartz.

Which of these metamorphic rocks formed from the sedimentary rock shale? Click on the correct answer. Slate (Correct, shale changed to form slate. Slate is much harder than shale and is used for chalk.) or Gneiss (Gneiss was not formed from a sedimentary rock. Try again.)

Which of these metamorphic rocks formed from the igneous rock granite? Click on the correct answer. Garnet mica schist (A mica schist is not formed from an igneous rock. Try again.) or Gneiss Correct, granite changed to form gneiss. Pressure caused the mineral grains to align.)

Which of these metamorphic rocks formed from the igneous rock granite? Click on the correct answer. Garnet mica schist (A mica schist is not formed from an igneous rock. Try again.) or Gneiss (Correct, granite changed to form gneiss. Pressure caused the mineral grains to align.)

Which of these metamorphic rocks formed from metamorphic rock slate? Click on the correct answer. Garnet mica schist (Correct, slate changed to form Garnet mica schist. Hot water helped alter the minerals in slate.) or Marble (The sedimentary rock limestone may change to form marble. Try again.)