Download Rocks - Middle School: BLRA

Rocks
 -naturally
occurring solid
mixture of one or
more minerals and
organic matter
 -make up Earth’s
crust
 Geologists
 Texture
 -persons
that collect
and study rocks
 -observe texture and
color
 -determine mineral
composition
 -look
and feel of
rock’s surface
 -ex. smooth, glassy,
rough, chalky
•
Grains
•
-particles of
minerals that give
rock texture
•
-large grains =
coarse grained
•
-small grains =
fine grained
– Size
• Shape of grains
 -wide
range of
different shaped
grains
 -ex. fine pieces of
sand, small seeds,
smooth, jagged
• Pattern
 -grains
form
patterns
 -ex. flat layers,
swirling patterns
• Not visible
 Igneous
Rock
 -no
visible grain
happens with fast
cooling
 -forms
from
cooling of molten
rock
 The
three main types
of rock are formed
during the rock
cycle.
•
Igneous Rock
•
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-any rock formed
magma or lava cooling
-“igneous” means
“fire”
-made of mineral
crystals
-exception: different
types of volcanic glass
-hard, dense, and
durable
-used for tools &
building materials
-classified by: origin,
texture, & mineral
composition
 Origin
 Extrusive
 -where
Rock
they are
formed
 -two types:
extrusive and
intrusive
 -formed
from lava
erupting on Earth’s
surface
 Fast cooling
 Small crystals
 -ex. Basalt and
Obsidian
 Intrusive
Rock
 -formed
when
magma hardens
below the surface
 Larger crystals
 Slow cooling
magma
 -ex. Granite; forms
core of many
mountains
 Sedimentary
Rock
 -forms
from other
rock, plant, &
animal remains
pressed together
 -forms in layers
 Sedimentary
Rock
 Sediment
 -forms
from particles
being weathered,
eroded, and
deposited by water
and wind are
cemented together.
 -small, solid
pieces of
materials that come
from rock or living
things
 *other things include:
shells, bones, leaves,
stems
 Erosion
 Deposition
 -running
water or
wind loosen and
carry away
fragments of rock
 -sediment
settles
out of water or
wind carrying it
 -after deposited;
compaction and
cementation
change the
sediment
 Compaction
 -process
that
presses sediments
together
 -happens over
millions of years
 -each year forms
new layers
compacted
together
 -minerals in rock
dissolve in water
during compaction
 Cementation
 -dissolved
minerals seep into
spaces
 -process where
dissolved minerals
crystallize and
glue particles of
sediment together
 Types
of
Sedimentary
Rock
 Clastic
Rock
 -3
major groups:
• 1. clastic rock
• 2. organic rock
• 3. chemical rock
• -rock fragments
are squeezed
together
• -grouped by size
of rock particles
of which they’re
made
 Shale
 -forms
from tiny
particles of clay
 -water deposits clay
in very thin layers
 -feels smooth & splits
easily
 Sandstone
 -forms
from sand on
beaches, ocean floor,
riverbeds
 -sand is compacted
and cemented
 -easily absorbs water
 Conglomerate
Breccia
&
 -mixture
of
fragments of
different sizes
 -round edges are
conglomerate
 -sharp edges are
breccia
 Organic
Rock
 -made
from living
things
• Coal
 -remains
of swamp
plants buried in
water
 -layers of decaying
plants are squeezed
 -forms coal over
millions of years
 Limestone
 -formed
from
coral, clams,
oysters, and snails
whose shells pile
up
 -shells are made of
calcite
 -calcite cements
shells together to
form limestone
 Chemical
 Uses
Rocks
of
Sedimentary Rock
 -minerals
dissolved
in solution
crystallize
 -also when seas
evaporate and leave
mineral deposits
 -ex. rock salt,
gypsum
 -used
in building
materials
 -decorating outside
walls of buildings
 -limestone used in
cement
 Metamorphic
Rocks
 -formed
when
existing rock is
changed by heat,
pressure, or chemical
reactions
 Meta (changed)
Morphos (shape)
 -forms deep
underground
 How
Metamorphic
Rocks Form
 -collisions
of Earth’s
plates push rocks
downward
 -deeper a rock is
buried, the greater
the pressure and
temperature.
 Classifying
Metamorphic
Rocks
 Foliated
 -classify
by
arrangement of
grains
 -grains
arranged
in parallel layers
or bands
 -thin, flat layering
 -may split apart
along bands
 -ex. slate, gneiss
 Nonfoliated
 Uses
of
Metamorphic Rock
 -grains
arranged
randomly
 -do NOT split into
layers
 -ex. marble &
quartzite
 -marble
(formed from
limestone) used for
buildings and statues
 -slate (formed from
shale) used for
flooring, roofing,
walkways, &
chalkboards
 Rock
Cycle
 -continual
process by
which new rock forms
from old rock
material
 -Earth’s constructive
and destructive
forces, like plate
tectonics, move rocks
through cycle
 Plate Tectonics
 -force
that drives the
rock cycle
 -push rocks back into
the mantle where
they melt and
become magma
 -causes folding,
faulting, & uplift that
move the rocks
 -two types cause
movement of rocks:
 1. Subducting
Oceanic Plates
 2. Colliding
Continental Plates