This resource is a set of revision notes on the CCEA GCSE topic of earth’s structure and rocks. It includes subtopics such as structure of earth, crust, rocks in Northern ireland, igneous rocks, sedimentary rocks, metamorphic rocks, plate tectonics theory, constructive plate boundaries, mid-ocean...
Inner
core-‐
solid,
made
mostly
of
iron
and
nickel
and
very
hot
with
temperatures
reaching
up
to
6,000
C.
It
is
about
2,200km
deep.
Outer
core-‐
made
of
liquid
iron
and
nickel,
surrounding
the
inner
core.
It
is
about
1,200km
deep.
Mantle-‐
this
is
soft
semi-‐molten
rock
below
the
crust
where
temperatures
reach
Earth’s surface
about
3,
000
C.
It
is
the
thickest
layer
at
about
2,900km
and
is
made
of
silicate
rocks.
The
mantle
layers
are
sometimes
known
as
the
asthenosphere.
Crust-‐
the
hard
outer
shell
of
Earth.
It
can
be
continental
or
oceanic
and
is
cracked
into
large
pieces
called
plates.
The
crust
and
more
solid
part
of
the
mantle
are
sometimes
known
as
the
lithosphere.
Oceanic
crust-‐
made
mostly
of
basalt
and
is
easily
destroyed
as
it
can
sink
into
the
mantle
Continental
crust-‐
is
made
mostly
of
granite,
is
hard
to
destroy
and
does
not
sink
easily
into
the
mantle
Oceanic
crust
Continental
crust
Density
3.0g/cm
2.7g/cm
Thickness
5km
20-‐50km
Age
Geographically
young
Can
be
very
old
Colour
Dark
Light
Chemical
elements
Rich
in
iron
and
magnesium
Rich
in
sodium,
potassium,
calcium
and
aluminium
Rocks
in
Northern
Ireland
Sedimentary
rocks
for
example
chalk
and
sandstone
are
sound
in
several
places
across
Northern
Ireland.
Sandstone
is
found
near
the
Belfast
area
and
he
North
Coast.
Chalk
can
be
found
in
narrow
bands,
near
sandstone
and
basalt.
Igneous
rocks
for
example
granite
and
basalt
can
be
found,
mainly,
in
two
different
positions:
Northeast
and
Southeast.
Basalt
is
the
dominant
rock
type
in
Northern
Ireland.
The
only
metamorphic
rock
is
the
Pre-‐Cambrian
Schist
and
is
found
in
the
Northwest.
Igneous
rocks-‐
rocks
that
form
as
a
result
of
volcanic
activity
when
lava
erupts,
cools
and
solidifies
containing
crystals.
E.g.
basalt
and
granite
Rock
Location
Characteristics
Formation
Uses
Basalt
Giant’s
• Very
dark,
almost
black
• After
a
volcanic
eruption,
lava
reaches
the
To
surface
causeway
• Fine
grained
crystals
surface
ad
if
the
molten
rock
cools
quickly
such
roads
Co.
(1mm)
as
when
it
is
in
contact
with
seawater,
basalt
Antrim
• Can
contain
bubbles
of
may
form.
gas
that
were
trapped
• The
crystals
in
basalt
are
very
small
because
as
the
lava
cooled.
the
cooling
of
the
rock
happened
so
rapidly
and
they
did
not
have
a
chance
to
grow.
Granite
Mourne
• Light
grey
(speckled)
• During
volcanic
activity,
molten
rock
may
not
Attractive
Mtns
• Larger
grains
(up
to
reach
the
Earth’s
surface
but
may
cool
deeper
when
Co.
Down
5mm)
down
polished
so
• So
it
takes
longer
for
the
cooling
rock
to
good
for
become
solid
gravestones
• The
slow
cooling
allows
crystals
to
grow
bigger
and
and
form
granite
kitchens.
Sedimentary
rocks-‐
rocks
that
form
from
sediments
that
have
fallen
to
the
bottom
of
a
lake
or
sea
and
have
been
compressed
into
rocks.
E.g.
limestone
and
sandstone
1. Land
is
worn
away
and
sand
and
mud
are
carried
to
the
sea
2. Sand
and
mud
settle
on
the
sea
bed
3. Layers
build
up
and
form
rock
such
and
sandstone
and
shale
4. Out
at
sea,
skeletons
of
tiny
sea
creatures
build
up
on
the
sea
bed
forming
chalk
and
limestone
Rock
Location
Characteristics
Formation
Uses
Limestone
Marble
• Made
of
calcium
• Millions
of
years
ago,
dead
sea
• Quarried
for
Arch
carbonate
(CaCO3)
creatures
and
shells
collected
on
the
cement
and
Caves,
• Remains
of
shells
and
sea
floor
as
sediment
lime
Fermanagh
skeletons
of
small
• Over
millions
of
years
the
layers
grew
• Important
, marine
organisms
E.g.
and
became
so
heavy
that
the
tourist
sites
coral
which
lived
in
sediment
got
compacted
and
warm
clear
seas
cemented
into
limestone
rock
which
• Grey
is
made
of
calcium
carbonate
• Dissolves
slowly
in
• When
sea
levels
dropped
or
seabed
rain
water
raised
up,
limestone
became
visible
Sandstone
Belfast
• Sandy
coloured
• Over
millions
of
years,
sand
and
• Building
• Sand
grans
0.05mm-‐ particles
gathered
as
sediment
on
the
materials
2mm
and
cemented
seabed
(transported
by
rivers)
or
on
• Sites
for
together
land.
many
• The
layers
slowly
grew
and
became
settlements
so
heavy
that
the
grains
of
sand
got
compacted
and
cemented
into
sandstone
rock
containing
quartz
minerals
Metamorphic
rocks-‐
rocks
that
have
been
altered
by
extremes
of
heat
and
pressure
into
a
different
rock.
E.g.
Slate
and
Marble
Name
Characteristics
Formed
Uses
Shale
• Dark
grey
• When
plates
collide
at
plate
boundaries
mountains
can
• Roofs
-‐
• Fine
grained
crystals
be
formed
• Seen
Slate
• Crystals
lie
in
same
• The
rocs
in
the
mountains
are
squeezed
by
tectonic
mostly
on
direction
allowing
forces
old
them
to
split
easily
• If
shale
(sedimentary)
is
exposed
to
great
heat
and
buildings
pressure
in
this
process,
its
properties
change
and
it
in
NI
becomes
slate
Limestone
• White/grey
• Limestone
may
get
exposed
to
high
temperatures
due
• To
make
-‐
• Made
of
Calcium
to
p late
m ovements
a long
b oundaries
statues/
Marble
carbonate
• This
melts
rock
before
it
recrystallises
to
much
larger
• Fireplaces
• Large
crystals
particles
o f
c alcium
c arbonate
w ith
d ifferent
characteristics
• It
becomes
marble,
which
has
a
similar
white/grey
colour
to
that
of
limestone.
Plate
tectonics
theory
• Plates-‐
huge
slabs
of
the
earths
crust
that
float
like
rafts
on
the
semi-‐solid
magma
• Plate
boundary-‐
place
where
plates
meet
• Move
at
an
average
speed
of
70mm
a
year
• Developed
in
1960-‐70s,
came
from
view
that
all
of
the
continents
seemed
to
fit
together.
About
250million
years
ago
the
continents
were
joined
as
Pangea.
• Evidence-‐
the
east
coast
of
South
America
and
the
west
coast
of
Africa
appear
to
fit
together
like
a
jigsaw.
Why
do
plates
move?
• Hot
currents
in
the
mantle,
called
convection
currents,
move
heated
molten
material
upwards
from
the
core,
towards
the
crust
• The
current
spread
out,
cool
and
sink
back
down
to
the
core
but
as
they
do,
they
create
frictional
drag
under
the
crust,
dragging
plates
in
different
directions
• This
is
how
and
why
plates
move
Constructive
plate
boundary-‐
where
two
plates
move
away
from
each
other
due
to
convection
currents
in
the
mantle,
creating
new
crust
between
them.
E.g.
Eurasian
and
North
American
plate
moving
apart
in
the
middle
of
the
Atlantic
Ocean
causes
the
ocean
to
get
wider
by
3cm
a
year.
Iceland
was
formed
in
this
way.
Cause-‐
convection
currents
in
the
mantle
create
a
frictional
drag
below
the
plates
pulling
them
in
opposite
directions.
This
movement
creates
a
gap
where
magma
wells
up
from
the
mantle
to
plug
the
gap.
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