Name: __________________________________
8th Grade Science
Earth Surface
Date: _______________
Mr. Vorstadt
Metamorphic Rock
The word metamorphic means,
“changed form”. Metamorphic rocks
result from changes in other rocks
caused by intense heat and/or
pressure without melting.
Metamorphic rocks began as igneous
or sedimentary rocks.
Metamorphism causes new minerals to
form. crystals to grow, structures such
as sedimentary layers to become
distorted and density to increase.
The diagram above shows that as sediments
like clay are buried deeper within the Earth,
heat and pressure increase causing the
sediments to change into shale, a
sedimentary rock. The shale is changed by
deeper burial through slate, phyllite “fill’ ite”)
schist and gneiss (“nice”). Still higher
temperatures and deeper burial could cause
the rock to melt. Then, cooling and
crystallization would produce an igneous rock.
Many metamorphic rocks display both
mineral crystals and layering. although
the layering may be the result of crystal
growth, and not the remains of original
sedimentary bedding. The alignment of
mineral crystals is known as rogation"
Foliation is a common property of
metamorphic rocks.
Metamorphic rocks can be placed on a
continuum from relatively slight changes to
higher grade rocks that have undergone more
extensive alteration. The greater the changes
caused by metamorphism, like foliation and
formation of new minerals, the higher the
grade of metamorphism.
The second diagram shows that there are two kinds of metamorphism. Contact
metamorphism occurs adjacent to an igneous intrusion, where the rocks in contact with
the intrusion have been baked. But, when a large mass of rock is buried deep within the
Earth, heat and pressure can cause widespread regional metamorphism.
Most of the rocks of Westchester probably began as a mixture of sedimentary and
igneous rocks, including sandstone, shale, limestone and basalt. Burial at a depth of
20-30 kilometers changed these rocks into their metamorphic products; schist, gneiss,
and marble. Research by geologists at Columbia, Yale and other universities has shown
that these rocks were buried about 25 kilometers beneath a great mountain range.
1. Metamorphic rock form under conditions of ____________________________ and
______________________________
2. What are metamorphic rocks made from? __________________________________
3. As rock is metamorphosed, __________________ form and grow larger.
4. The two types of metamorphism are ____________________ and _______________
5. Which kind of metamorphism occurs next to intrusion of molten magma? __________
6. What is foliation? ______________________________________________________
7. If clay is buried very deep within the earth, it can progress through a series of
metamorphic rocks of increasing metamorphic grade. Name the rocks in this series.
(Hint: See the top on page 1) ____________________________________________
___________________________________________________________________
8. What change happens to all igneous rocks, but not metamorphic rocks? __________
9. What kind of rock is the most common in Westchester? Sedimentary, Metamorphic
(Circle one Please)
10.
What conditions cause metamorphism? ________________________________
11.
What changes happen to rock when it becomes a metamorphic rock? (Please
list three changes.)___________________________________________________
___________________________________________________________________
___________________________________________________________________
Metamorphic rocks are usually classified as foliated or non-foliated. The foliated rocks
have a streaked, layered or banded appearance caused by the parallel growth of
mineral crystals. The non-foliated rocks contain very small crystals or the crystals show
no preferred alignment Remember that foliation means that the crystals are lined up
parallel to each other giving the rock a layered look. Foliation means crystal alignment
12.
Which foliated metamorphic rock has the smallest crystals? _________________
13.
What mineral is commonly found in most foliated metamorphic rocks? ________
14.
What sedimentary rock change into marble? _____________________________
15.
What is antrracite made from? ________________________________________
16.
What mineral family is found in schist, geniss, and slate? ___________________
17.
Which two metamorphic rocks are composed of the largest crystals?__________
___________________________________________________________________
18.
19.
Which metamorphic rock is monomineralic? _____________________________
(That is, it generally contains only one mineral)
What is slate made from? _________________________
20.
Marble is made from? __________________________