Heat an
nd pressurre can cha
ange many things. Th
hey can evven change
e rocks. The
T
name fo
or rocks that has be
een change
ed is meta
amorphic (met uh MO
OR fik) ro
ocks.
Metamo
orphic com
mes from Greek
G
word
ds meaning
g "change" and "form
m".
Metamo
orphic rock
ks form de
eep in the earth where high
tempera
ature, gre
eat pressurre, and ch
hemical rea
actions cau
use one
type of
f rock to change
c
into
o another type of ro
ock. Meta
amorphic
rocks begin
b
to fo
orm at 12-16 kilome
eters bene
eath the ea
arth's
surface. They beg
gin changin
ng at
temperattures of 100
1
degree
es Celsius to 800
degrees Celsius. If
I you sque
eeze and heat
h
a
rock for a few milllion years, it can tu
urn into
a new kin
nd of rock
k.
Where does
d
the heat
h
come from? The
e heat
comes frrom magma
a. Where does the pressure
come frrom? The pressure comes
c
from
m layers of
o rock pile
ed on top
of layerrs and layers of roc
ck. The lay
yers on th
he bottom get
squeeze
ed. The th
hicker the layers, th
he more prressure th
here is.
Some examples of how mettamorphic rocks werre changed
d:
ary of the major cha
aracteristiics of mettamorphic rocks.
Below iss a summa
Classified
d by textu
ure and co
omposition
Rarely ha
as fossils
May reac
ct with acid
http://librrary.thinkquest.org/J002289/metta.html May have
e alternate
e bands of
f light and
d dark min
nerals
May be composed
c
o only one mineral, ex. marb
of
ble & quarttzite
May have
e layers of
f visible crystals
Usually made
m
of mineral crysstals of diifferent siizes
Rarely ha
as pores or
o openingss
May have
e bent or curved folliation
Here's a checklist of some common me
etamorphic
c rocks and
d their
charactteristics. Look
L
for these
t
same
e characte
eristics in the rocks you find, and
you
u'll be welll on your way
w
to bec
coming a rockhound
r
.
So
ome Co
ommon Metam
morphic Rocks
Name
N
Colo
or
T
Texture
Gneiss
G
Pink/G
Gray
Foliated
Marble
M
Light Co
olored
U
Unfoliated
Qu
uartzite
Light Co
olored
U
Unfoliated
Slate
S
I
Image
D
Dark
Gray to Black Foliated
To lea
arn more about
a
rockss and mine
erals, click
k next belo
ow:
http://librrary.thinkquest.org/J002289/metta.html