What’s So Special
About ROCKS?
Rock Note Guide
ROCKS are….
•
A naturally occurring solid
mixture of one or more
minerals, or organic
matter.
Rocks are classified by….
• Texture: the grain size and the way grains fit together
• Visible or no visible grains, shape, pattern, or overall look
and feel
• Textures are determined by the environment in which the
rock is formed.
• Composition: the minerals or grains found inside the rock
• Whether it was formed in a volcano or alongside a river.
Types of Rocks
• The three main kinds of rock are igneous, sedimentary and
metamorphic rock.
• Igneous rock: forms when magma/lava cools and hardens
• Sedimentary rock: forms from organic and inorganic
sediments
• Metamorphic rock: forms when existing rock is subjected to
great heat & pressure over a long period of time
Igneous Rocks
• Ignis” = Latin for “fire”
• It is also called PORPHYRITIC meaning, it’s
a rock that has distinct difference in it’s
size of crystals.
• Which these are formed from the cooling
of either magma or lava
• The most abundant type of rock
Forms BELOW
ground…Intrusive
• Magma cools under Earth’s
Surface
• Coarse Grained
• Usually have LARGE
crystal grains (due to
cooling slowly over a
long period of time)
Examples of Intrusive Igneous Rock
Forms ABOVE
ground….Extrusive
• Lava cools above Earth’s
surface.
• Fined grained
• Usually has SMALL or NO
crystals (due to cooling too
quickly)
Examples of Extrusive Igneous Rocks
Sedimentary Rocks
• Formed from sediments
(rock fragments, mineral
grains, animal & plant
remains-shells, bones,
leaves, stems).
Process to Make
Sedimentary Rocks
• 1. Weathering/Erosion: where sediments get broken apart by
natural force like wind, water, then transported to a new
location.
• 2. Deposition: where sediments get laid down or placed in that
new location, then can start accumulating in layers.
• 3. Compaction: where the weight from the layers of sediments
forces out fluids and decreases the space between the grains
• 4. Cementation: where minerals dissolved in water crystallize
between sediment grains, holding the grains together.
3 Types of Sedimentary Rocks
• Clastic (also called Detrial)—made of broken pieces of other
rocks. Formed when rock fragments are squeezed together.
Clastic-Sedimentary Rocks
• Shale: Formed from tiny
particles of clay
compacted together.
• Sandstone: Forms from
the compaction and
cementation of small
particles of sand.
Clastic-Sedimentary Rocks
• Conglomerate: Formed from
fragments of various sizes of
rocks and pebbles. Fragments
are rounded because they have
been worn along riverbeds.
• Breccia: Fragments are jagged
with sharp edges. Formed from
various size of rocks and
pebbles.
3 Types of Sedimentary Rocks:
Organic—remains of plants and animals are
deposited in thick layers
• Organic refers to substances that once were
part of living things or were made by living
things which contain calcite or calcium
carbonate. (Can be tested by using acid)
Organic-Sedimentary Rocks
• Coal: Remains of swamp plants
buried in water or by volcanic
ash.
• Limestone: Formed by hard
shells of once living things such
as coral, clams, oysters, and
snails. When they die their
shells pile up and are covered
by other sediments compacting
and cementing them.
3 Types of Sedimentary Rocks:
• Chemical—
minerals
dissolved in lakes,
seas, or
underground
water. Can occur
when lakes
evaporate.
Chemical-Sedimentary Rocks
• Rock Salt: Made of
the mineral halite.
• Gypsum: Formed by
evaporation in dry
climates.
Metamorphic Rocks
• Rocks that have changed due to intense temperature and
pressure
• “Meta” means “change” and morphosis means “form” in
Greek
• Igneous, sedimentary and other metamorphic rocks can
change to become metamorphic rocks
What occurs in the Earth to change
these rocks?
• Pressure from overlying rock
layers
• High heat, but not enough to melt
the rock
• Rocks may be flattened or bent
or atoms may be exchanged to
form new minerals.
Where do metamorphic rocks usually
form?
• Where magma intrudes relatively cool
•
•
•
•
•
rock
Near colliding plates (near mountain
ranges)
Places that are covered miles thick with
other rock causing pressure
When hot water intrudes rock
Where a meteorite strikes Earth (rare)
Where lightning bolts strike rocks (rare)
Classification of Metamorphic Rocks
• Foliated—mineral grains are
flattened and line up in parallel
bands or layers.
• Example: gneiss formed from
rearrangement of minerals in
granite into bands
• Examples: Gneiss, Slate, Schist
Classification of Metamorphic Rocks
• Non-Foliated—No bands
are formed
• Re-crystalization
• Example: marble formed
from limestone
• Other examples:
quartzite, Diamonds
Rocks
Transformed
Limestone
Shale
Marble
Slate
Rocks
Transformed
Sandstone
Mudstone
Quartzite
Schist
or
Gneiss