Transcript SEDIMENTARY Rocks - School

Y7 Rocks and the Rock
Cycle C7.3
Lesson 1 – Igneous rocks
Rocks come in various different forms:
Igneous
Sedimentary
Metamorphic
Where does the word ‘igneous’ come from?
from Latin igneus fiery, from ignis fire (think of
ignition – to set fire to)
This is because igneous rocks are made from
volcanic eruptions which look like fire!
Under a microscope…
Igneous rocks have
interlocking grains –
these grains are
crystals formed when
liquid rock in the
centre of the Earth
cools
Gabbro is made of coarse-grained (5mm or so) interlocking crystals. Its overall colour is
dark grey but it often contains glassy or pale-coloured crystals of feldspar as well as dark
minerals.
Granite is made of coarse-grained (5mm or so) interlocking crystals. It has more light
coloured crystals than dark, usually of white or pink feldspar, glassy quartz, and shiny
mica
Basalt is made of fine-grained interlocking crystals (about 1mm in size). It
is black or dark grey in colour, and often contains vesicles – bubbles of
gas trapped as the lava cooled.
Dolerite - extrusive
Fast cooling
Small crystals
Slow cooling
Big crystals
Consider the two sites; which
would have large crystals in the
rock formed and which would have
smaller ones….why?
Lesson 2 – Weathering
Weathering
Physical
Chemical
Biological
Physical weathering
Physical weathering
Frost shattered rock
Physical weathering
Antarctic rocks – what
do you think has
weathered them?
Sandstone in the
desert in Nevada –
what do you think
has weathered
them?
Biological weathering
Biological weathering
Chemical weathering
Chemical weathering
Limestone pavements in
Yorkshire (Ravenscar and
Malham)
Chemical weathering
St Bartholomew’s Manhattan
Lesson 3 – Erosion and
deposition
http://www.bbc.co.uk/learningzone/clips/the-river-conwy-erosion-and-deposition/3237.html
WEATHERING
= the break up of rocks into bits (while the
rock stays where it is)
EROSION
= the break up of rocks into bits (while the
rock is moving)
Erosion
These pebbles are smooth as other rocks
have rubbed into them over time and broken
off the sharp edges
Erosion
This river bend has been formed by the water
wearing away the rock
Erosion
The wind has formed this shape of rock
Deposition
Deposition: Stones are picked up by the
water and moved from one place to another
Will all rocks move the
same amount?
Deposition
Stones are picked up by the water and moved from one
place to another
Lesson 4 – Sedimentary
Rocks
sandstone
sand
conglomerate
pebbles
• What do they have in common?
• How do you think they are made?
SEDIMENTARY Rocks
sand
sandstone
mud
mudstone (shale)
shells
limestone
Under a microscope
you can see individual
grains ‘glued together’
How is this different in
appearance to igneous
rocks?
Nummulitic limestone.
Polarised light micrograph of a thin section of a Nummulitic limestone
Layers of Sandstone and Mudstone
Sedimentary rock is made from other small
rocks, mud, dead animals or sea creatures,
sand, all built up over years in layers
SEDIMENTARY Rocks
DEPOSITION - sediment sinks to the bottom of the sea
COMPACTION - sediment squashed by more sediment
CEMENTATION - sediment cemented together by
minerals from the water
FOSSILS
• they are imprints of the remains of living creatures
• they are found in sedimentary rocks (creatures remains fall
into sediment)
• they are not found in igneous/metamorphic as the
heat/pressure in their formation would destroy the remains
Lesson 5 – Metamorphic
Rocks
sandstone
metaquartzite
mudstone (shale)
slate / phyllite /
schist / gneiss
limestone
marble
METAMORPHIC Rocks
sandstone
mudstone (shale)
Heat and/or pressure acting
on other rocks – changes
them (without melting)
limestone
slate / phyllite /
schist / gneiss
metaquartzite
marble
Effect of HEAT
Effect of PRESSURE
Interlocking grains
and then clear layers
of crystals in ‘bands’
How is this different
and /or similar to
igneous and
sedimentary rocks?
Gneiss is made of
coarse-grained
interlocking
crystals. Crystals
line up in pale and
dark layers to give
the rock a banded
texture
Schist is made of
medium-grained
interlocking crystals.
Its shiny appearance
is due to the mineral
mica. Crystals line up
to give the rock
wrinkly layers – this is
called foliation.
Marble (metamorphosed
limestone) is made of
calcium carbonate (fizzes
with acid). It has mediumgrained Interlocking crystals
with no alignment.
Lesson 6 – The Rock Cycle
Weathering & erosion
SEDIMENT
Deposition &
cementation
SEDIMENTARY
ROCK
Heat & pressure
Weathering & erosion
Weathering & erosion
IGNEOUS
ROCK
Heat & pressure
Cooling &
crystallisation
METAMORPHIC
ROCK
Melting
MAGMA