Download Rocks - West Ada

Rocks
THE ROCK CYCLE
CLASSIFYING ROCKS
What is a rock?
A group of minerals bound together in some way.
The Rock Cycle
A series of processes
above/below the Earth
that change rocks from
one kind to another
over time!
Can follow various paths
The food web of
geology!
3 main types of rocks
1) Igneous -formed by…
2) Sedimentary- formed by erosion, pressure of layers of sediments
3) Metamorphic- formed by heat/pressure over time.
Molten rock- formed by melting
https://www.youtube.com/watch?v=6bkyXvYP4jM
How do we classify rocks?
Color
Texture
Mineral composition
(remember minerals
make up rocks)
Texture
Size, shape and pattern of the rock grains (particles of minerals)
Smooth/glassy
Rough/chalky
Grain size
Large- easy to see ? (course grains)
Small- fine grained
Grain shape
Round?
Jagged?
Stars?
Stripes?
Grain pattern
Flat (like a pancake)
Wavy/swirling
Bands
No visible grain?
In this case it means the
rock cooled quickly!
It probably has a
smooth/shiny texture like
glass…
Mineral composition
Look at the size/shape of crystals
Coloration
Origin
Can you
identify which
of the three
major types of
rocks it is?
https://www.youtube.com/watch?v=aSLs2ek6Azs
https://www.youtube.com/watch?v=2RZMXd4IAb0
Igneous Rocks
Rocks that formed from magma/lava
“fire”
Most have mineral crystals
Hard, dense, durable rocks
https://www.youtube.com/watch?v=PrN7jygu4cQ
Igneous rocks are used for
2 origins of igneous rocks
1) Extrusive/Volcanic – from lava
Forms outside of the volcano on the surface.
Example- basalt
2) Intrusive/Plutonic- forms from magma cooling
below surface
Continents and mountain ranges can be intrusive
Example- granite
Texture of igneous rocks
Texture can vary
Rapid cooling (small crystal
structures, fine grains)
Slow cooling (large crystals,
course grains)
Mineral composition of igneous rocks
Silica
Amount of silica present
can determine color of
igneous rocks
Let’s look at igneous rocks!
Sedimentary Rocks
Form from particles (sediment) deposited from water
and wind.
https://www.youtube.com/watch?v=NX0kPo2mMC4
https://www.youtube.com/watch?v=04a_32NuYqs
Process of sediment to rock…
1) Erosion- water/wind or other forces carry away rock fragments.
2) Deposition- sediment is eventually separated or “deposited.”
3) Compaction- sediment is crushed or pressed together
4) Cementation- dissolved minerals crystalize and glue together (forming a rock)
3 major types of sedimentary rocks
1) Clastic- formed from rock fragments being squeezed
together.
Organized by size of grain/size of fragments.
Examples:
Shale- forms from clay, often soft, splits into flat pieces
Sandstone- feels gritty, forms from sand, contains quartz
Conglomerate and Breccia- rocks within rocks, vary in size.
Look for shape of rocks within (round- conglomerate,
jagged- breccia
Organic rocks- formed from plant/animal remains.
Were once “living.”
Examples:
Coal- remains of swamp plants buried in mud/water.
Limestone- shells of animal remains (calcite) pile up
and cement together. (Not all limestone has visible
shells and skeletons). Compact and shell limestone.
Chalk- is another form of limestone.
Chert/Flint- sharp edges, used for tools
Chemical rocks- form from minerals being dissolved in solutions and crystallizing. Can form from
evaporation of liquid.
Examples:
Halite (rock salt) Gypsum-
Uses of sedimentary rocks
https://www.youtube.com/watch?v=W4a3AzDYm2M
Metamorphic rocks
Meta “change”
Morphosis “form”
Formed from heat and
pressure
Can form from igneous,
sedimentary or from other
metamorphic rocks.
https://www.youtube.com/watch?v=Uuzmub5PXNQ
Classifying metamorphic rocks
Heat can change the crystal size
and shape of mineral grains
Pressure can rearrange the
organization of minerals
Rocks that have parallel grains
are “foliated”
Uses of metamorphic rock
Marble
Slate
Weathering/Erosion of Rocks
https://www.youtube.com/watch?v=p2X4U1mQzoE&list=PLXR
_HtDPvlm8tvSbWQVwEKBdLmFbpBhMV
https://www.youtube.com/watch?v=oFnpm4SUF7I&index=2&li
st=PLXR_HtDPvlm8tvSbWQVwEKBdLmFbpBhMV
Weathering
Process that breaks down
rocks and other substances
over time.
Water, wind, heat, cold, salt,
and ice can weather
materials.
Erosion
Movement of rock
particles (sediment) by
wind, water, ice or
gravity.
Works with weathering
Slow process
https://www.youtube.com/watch?v=ktf73HNZZGY&list=PLXR_
HtDPvlm8tvSbWQVwEKBdLmFbpBhMV&index=4
Mechanical Weathering
Physical breakdown
of rocks (cracking,
peeling)
Freezing/Thawing
Pressure
Animals breaking
apart
Sediment has similar
chemical composition
as original rock.
Chemical Weathering
Breaks down rock
through chemical
changes/reactions
Acid rain, water,
oxygen, carbon
dioxide
Sediment has a
different chemical
composition than
original rock
Factors that influence weathering
1) Climate
Wet climates weather faster
High temperature increases
weathering
2) Type of rock
Minerals in rock determine how
fast it weathers
Are they water soluble?
Permeable?