ROCKS Flashcards
Define Rock
naturally occurring solid mixture of one or more minerals or organic matter
how are rocks classified?
- how they are formed
- composition (what they are made of)
- texture
Rocks change over time via what?
Rock Cycle
what are the three types of rocks
igneous, sedimentary, metamorphic
igneous rocks form from what
cooled liquid magma
Any rock can become an igneous rock if
it’s melted into magma
when magma reaches earth’s surface, it is called
lava
We identify igneous rocks by…
texture and color
how many types of texture?
four
how is texture determined?
how quickly a rock cools
the cooling rate determines what
the size of the minerals within the rock
texture describes what two things..
crystal size and appearance
What are the 4 types of texture (by speed of cooling)
pyroclastic (fastest)
froth
fine-grained
intrusive (slowest)
What does pyroclastic mean?
Formed by explosion
what is another word for pyroclastic
fragmental texture
pyroclastic are the _______ and _______ that are blown into atomosphere
ash and cinders
because pyroclastic cools so quickly…
no crystals form and ashes and cinders are cemented together
Froth is magma that is cooled by
water or forced far from the source of heat
Do crystals form with pyroclastic or froth?
NO
the texture of froth is called
glassy or vitrous
Name another name for volcanic glass
Obsidian
Pumice, which is not smooth is formed from…
froth
obsidian is formed from..
froth
fine-grained is magma that cools..
above the Earth surface
fine grained magma forms crystals that…
aren’t visible
when crystals are not visible it’s called
extrusive
extrusive rocks have _______ appearance
uniform
The slowest cooling rocks are called
intrusive
intrusive rocks cool where
within the Earth
intrusive rocks have _______ texture
coarse
what does coarse texture mean?
You can see the crystals that have formed. You may even be able to identify different minerals.
depending on where/how a volcano forms, the magma will dissolve a different amount of
silica
silica makes up what percent of Earth crust
95%
what is another word for silica?
silicon dioxide SiO2
magma inside the earth is made primarily of..
..heavy metals
amount of Earth’s crust dissolved by magma rising to surface is correlated to
amount of silica added to magma
felsic rocks are (color)
light in color
felsic rocks are low in _______ and high in ______
low = heavy metals and high = silica
FEL in felsic is for
potassium feldspar
SIC in felsic is for
silica
felsic have specific gravity of
less than 3.0
felsic is lighter because they contain less
metals
mafic rocks are (color)
dark
mafic rock contain silica but have higher amounts of
heavy metals
MA in mafic comes from
magnesium
FIC in mafic from
Latin word for iron
mafic have specific gravity of
more than 3.0
intermediate are somewhere between
felsic and mafic
Intermediate color is
grey or brown–neither very light or very dark
the word intermediate means
in the middle
Ultramafic are extremely
DARK and HEAVY
Ultramafic rocks have very high percentages of
heavy metals
Sedimentary rocks from when
bits of sediment are compacted and cemented together
to become a sedimentary rock, it first need to be
sediment
sedimentary rocks are made of
sediment but can also consist of organic matter compacted/cemented together
sedimentary rocks are classified by
rock type, texture and structure
what are the three types of sedimentary rocks
Clastic/detrital, chemical or organic
What is a clastic/detrital rock
pre-existed rock compacted/cemented together
A Clastic or detrital rock can be what sizes
boulder, pebble, sand, silt/clay
Chemical sedimentary rock forms how?
when bits of pre-existing rock and minerals are dissolved in a solution (usually sea water) are cemented together as the solution evaporates.
Give two examples of chemical sedimentary rock…
rock gypsum and rock salt
How is organic sedimentary rock formed?
when organic matter is compressed and cemented together.
Give examples of organic sedimentary rock
coal, limestone, limestone coquina
How is texture determined
by the visibility of the particles of the rocks
what is the range of texture?
fine, medium and coarse
If a rock’s texture has uniform color and visible sediments the texture would be
fine
if a rock’s color is mostly uniform and small particles visible what is texture
medium
if a rock is composed of large, obvious particles what is texture?
coarse
STructure describes the what of a rock
APPEARANCE
If the structure is FRAGMENTAL it means
it is obvious that different types of particles are cemented together
if the structure of a rock is GRANULAR
it appears to be grainy, composed of sand-sized particles or smaller
If the structure of the rock is CRYSTALLINE
it means crystal shape is evident in structure of the rock
if the structure of the rock is GLASSY
it means the rock is shiny or scratchy in appearance
if the structure of the rock is RESINOUS
it means the rock appears to contain resin (produced by trees and plants)
How do METAMORPHIC rocks form?
when existing rocks of any type are pushed deep within the Earth and are exposed to extreme heat and pressure
in METAMORPHIC rocks the heat and pressure
cause partial melting and compression of the existing rock
two ways metamorphic rocks are classified
foliated and non-foliated
some Metamorphic rocks have a banded appearance which means
the rock has stripes or alternating layers of color
foliated rocks often cleave along
their layers
non-foliated metamorphic rocks have no
visible layers and often have complete fracture (or do not break along clear surface)
what is difference between foliated and non-foliated metamorphic rocks
foliated = layers non-foliated = no layers
Metamorphic rock texture means
the size of visible crystals
when no crystals are visible we say
the rock is FINE GRAINED
when crystals are obvious we say
COARSE GRAINED
when rocks have a range of crystals–fine to coarse we say
medium grained
what is a parent rock?
what rock the metamorphic rock came from i.e. before it was exposed to extreme heat and pressure
If we can identify a parent rock of a metamorphic rock we can
make connection between rocks we can identify and visualize the rock cycle process
What is the rock cycle?
(look at diagram on study guide)
