Transcript Topic II (Continued)  Igneous Rocks Sedimentary Rocks

Topic II (Continued)
What are “Rocks”
 The Rock Cycle
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
Rocks are mixtures of minerals..
There are 3 major classes of rock.
• Igneous rocks
form when hot
molten rock
material cools
and hardens.
Sedimentary Rocks
• Sedimentary rocks
form when bits and
pieces of other rocks
are weathered and
eroded away,
accumulate (usually in
a large body of water),
and are cemented
together.
Metamorphic rocks…..
• form when other
rocks are altered
by heat, pressure,
and/or chemical
action.
The rock cycle “begins” with
each of the 3 major rock
groups….
Igneous
Metamorphic
Sedimentary
Igneous rock can weather and
erode to from sediments...
Igneous
Metamorphic
Sediments
Sedimentary
Which can be cemented together
to form Sedimentary rocks
Igneous
Metamorphic
Sediments
Sedimentary
These rocks can then melt to
form magma...
Igneous
Metamorphic
Magma
Sediments
Sedimentary
Which cools and hardens to form
Igneous rock
Igneous
Metamorphic
Magma
Sediments
Sedimentary
The igneous rock could also be
heated &/or pressurized….
Igneous
Metamorphic
Magma
Sediments
Sedimentary
to form a new Metamorphic rock.
Igneous
Metamorphic
Magma
Sediments
Sedimentary
Or the Igneous rock could melt and
cool to form a new Igneous rock.
Igneous
Metamorphic
Magma
Sediments
Sedimentary
The Metamorphic rock could also
melt and cool to form a new Igneous
rock.
Igneous
Metamorphic
Magma
Sediments
Sedimentary
The Metamorphic rock could also
erode to form sediments….
Igneous
Metamorphic
Magma
Sediments
Sediments
Sedimentary
which is cemented together to form a
new sedimentary rock.
Igneous
Metamorphic
Magma
Sediments
Sediments
Sedimentary
The sedimentary rock can be heated &/or
pressurized to form a metamorphic rock.
Igneous
Metamorphic
Magma
Sediments
Sediments
Sedimentary
The sedimentary rock can be eroded to
form sediments…....
Igneous
Metamorphic
Magma
Sediments
Sediments
Sedimentary
Which are cemented together to form new
sedimentary rocks.
Igneous
Metamorphic
Magma
Sediments
Sediments
Sedimentary
Finally, the metamorphic rock can be
heated and pressurized….
Igneous
Metamorphic
Magma
Sediments
Sediments
Sedimentary
to form a new metamorphic rock.
Igneous
Metamorphic
Magma
Sediments
Sediments
Sedimentary
The Rock Cycle
Igneous Rocks
• Igneous rocks form when hot liquid
rock called magma (if it is deep
within the earth) or lava (if it is near
or at the earth’s surface) cools and
hardens.
Igneous rocks are classified as
being “Intrusive” of “Extrusive”
• Extrusive igneous
rocks (aka
“Volcanics”) form
as lava cools and
hardens at or near
the earth’s
surface.
“Fogol” erupts, throwing
extrusive rocks into the air……
“Intrusive” (aka “Plutonic”)
• These rocks
form deep in the
earth as magma
cools and
hardens.
Crystal size and cooling time...
• As minerals take form,
molecules “fall into
place” layer upon
layer in a definite
orderly pattern.
Minerals which cool
over a long period of
time will therefore
develop large crystals.
Rapid cooling, however….
• does not permit
the atoms to
arrange
themselves in an
orderly pattern.
Thus, rocks which
cool quickly
usually have a
glassy or fine
texture.
Igneous rocks can be identified
by their…..
• Color - Is the mineral dark or light ? This
color usually reflects the mineral
composition of the rock
• Texture - Is the rock coarse grained
(crystals are easily visible with the naked
eye), fine grained (crystals are only visible
with a magnifier) or glassy (no crystals are
visible even under magnification) ?
Use your Earth Science
Reference Tables to identify
igneous rocks….
If your sample is light colored..
and is fine grained…..
The rock must be Rhyolite