Download Metamorphic rocks

METAMORPHIC ROCKS
Metamorphism
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Metamorphic rocks: appear to have changed in
their structure or chemical composition since their
creation or formation.
Originally sedimentary or igneous
Altered by heat, pressure, or exposure to hot fluids
in earth’s crust
Metamorphism
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Two kinds:
 1.
Local metamorphism – rock materials that have been
heated and compressed by magma, so their crystal
structure and chemical composition has been altered.
[Mostly near active volcanoes]
 2. Regional metamorphism – large areas of
sedimentary rock that were folded in the past due to
immense forces. [Mostly during the Flood]
Classifying Metamorphic Rocks
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2 kinds:
 1.
Foliated – contains flattened mineral crystals aligned
in parallel layers and may break easily along these
layers
 2. Nonfoliated – not banded or layered and tend to
break into sharp, angular pieces
Foliated Rocks
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Common foliated rock = slate
 It
is the metamorphosed sedimentary rock shale.
 In the past, it was used for schoolroom black boards.
 Colors: black, gray, purple, red, and green
Foliated Rocks
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Geologists think that schists were formed when slate
was deeply buried and exposed to great pressure
and temperature.
Schist has many thin layers often highly folded and
a silky sheen.
The same minerals formed dense, foliated, coarsely
textured rocks with distinct bands of different
minerals called “gneiss” when under greater
metamorphic stresses.
Nonfoliated Rocks
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Common examples: marble and quartzite
Marble is metamorphosed limestone.
 Will
fizz when hydrochloric acid is applied
 “pure” = white (impurities cause color)
 Uses: monuments, gravestones, and countertops
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Quartzite is metamorphosed quartz sandstone.
 Intense
heat and pressure made crystals interlock
 Durable because all pores are filled with silica
 The
Lord is our Rock. (Matt. 7)