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Agenda
Jan. 29, 2013
Mr. King
1. Rock Powerpoint – take notes
2. Assignment #15: Rock or Mineral
Lab
3. Fossil Vocabulary
4. Homework: #19 Fossil Vocabulary
Flash Cards
ROCKS
TYPES OF ROCKS
AND THE ROCK CYCLE
Rocks or Mineral?
Rocks
• No definite
composition
Minerals
• Definite
composition
• Can have organic parts
• Inorganic –
• No definite properties
• Definite properties
• Classified by how formed
• Classified by composition
and crystal shape
•
no living remains
TYPES OF ROCKS
• Unlike minerals, rocks cannot be classified by
their properties
• Rocks are classified by HOW they formed
TEXTURE tells the pressure & temperature;
COMPOSITION tells where formed:
 Igneous: Melting & Cooling
 Sedimentary: Compacting & Cementing
 Metamorphic: Heat & Pressure
IGNEOUS ROCKS
Rocks that have been MELTED and COOLED
• magma: molten rock below earth’s surface
• lava: molten rock above earth’s surface
IGNEOUS ROCKS
MELTED & COOLED
Classified by HOW FAST and WHERE they cool:
• Intrusive rocks - cooled INSIDE the earth
Cooling takes a LONG time because the earth insulates
the heat; Slow cooling time means LARGE crystals
• Extrusive rocks - cooled OUTSIDE the earth’s crust
They are cooled quickly and form SMALL crystals
IGNEOUS ROCKS
MELTED & COOLED
Granite
Intrusive
Large grains
IGNEOUS ROCKS
MELTED & COOLED
Basalt*
Extrusive
Small grains
*makes up new ocean
floor
Gases released near
the surface of a lava
flow create bubbles or
that are “frozen” in
stone
IGNEOUS ROCKS
MELTED & COOLED
Pumice
Extrusive
-
Small grains
IGNEOUS ROCKS
MELTED & COOLED
Obsidian
Extrusive
Small grains - glassy
Snowflake
IGNEOUS ROCKS
Summary
HOT MAGMA
When magma (melted rock) cools &
crystallizes underground crystals grow
large, and the rock is called GRANITE.
When magma breaks through a
weak part of the earth's crust
the rock is called LAVA.
Crystals are too small to see
because volcanic rocks cool
quickly. Examples: BASALT,
SCORPIA, TUFF, PUMICE,
and OBSIDIAN
SEDIMENTARY ROCKS
• Formed by COMPACTION & CEMENTATION
• Composed of layers of sediments
• Process :
1. Weathering: breaking down of rock at the Earth’s
surface (mechanical or chemical) producing
Sediments (rock fragments, sand, mud)
2. Erosion: transportation of weathered rock pieces
3. Deposition: eroded particles settle (often in layers)
4. Compaction: pressure applied squeezes out water
5. Cementation: fills in the gaps and “glues” rock
SEDIMENTARY ROCKS
COMPACTED & CEMENTED
How to recognize sedimentary rocks:
• Composed of various rock fragments
• Composed of layers (strata)
• Can contain fossils
• Crumble easily
SEDIMENTARY ROCKS
COMPACTED & CEMENTED
CONGLOMERATES
form in stream beds
and pebble beaches
SEDIMENTARY ROCKS
COMPACTED & CEMENTED
SANDSTONE
made up of fine-grained particles,
has a sandy texture (feels gritty)
Sandstones form in sandy environments such as
beaches, sand bars, deltas and dunes
SEDIMENTARY ROCKS
COMPACTED & CEMENTED
LIMESTONE –
chemical
weathering
SEDIMENTARY ROCKS
Summary
Sedimentary Rocks, like
sandstone, shale, &
limestone are made
from PIECES that were
buried COMPRESSED)
& CEMENTED together.
METAMORPHIC ROCKS
Rocks changed by heat and pressure
• NO MELTING
• Recrystallization:
the crystals of old rock reform into new crystals and
sometimes new minerals
• Occurs below earth’s surface, usually between plates
• Foliated (distinct layers of flatten minerals) vs.
Nonfoliated (no layers)
METAMORPHIC ROCKS
PRESSURE & HEAT
SLATE - foliated
Parallel planes.
Gray, black, green or red.
Uses include roofing, fireplaces, and “blackboards”.
METAMORPHIC ROCKS
PRESSURE & HEAT
GNEISS – foliated
• Black and white banding
• Banding is “squiggly”
because heat makes the rock
“plastic (flexible)”
METAMORPHIC ROCKS
Summary
METAMORPHIC ROCKS
have been CHANGED because of
HEAT & PRESSURE
Sedimentary
Rocks
Metamorphic
Rocks
Igneous
Rocks
THE ROCK CYCLE
The Story of METACONGLOMERATE
Conglomerate
Once was a SEDAMENTARY conglomerate.....
• It was subjected to high temperatures
and pressure;
• The pebbles squished and elongated
to form layers (foliated)
• Kept pebbly appearance
• It became a metamorphosed
conglomerate, and received a new
name: metaconglomerate.
THE ROCK CYCLE
limestone
The Story of Marble
Once was a SEDAMENTARY limestone .....
• It was subjected to high temperatures and pressure;
• The layers were flattened and twisted
• It became a metamorphosed limestone, and
received a new name: marble.
• People polished it and used it
in their homes as tiles. Some
marble was even carved into
statues!
Metamorphosis of Shale to Gneiss
From Sedimentary to Metamorphic
SHALE is the most common sedimentary rock.
Through pressure and heat, (metamorphism), it changes into
other rocks.
These changes take place without melting the rock!
Shale
Increasing Temperature and Pressure
Slate
Phyllite
SHALE becomes SLATE
Schist
SLATE becomes PHYLLITE
PHYLLITE becomes SCHIST
SCHIST becomes GNEISS
Gneiss
Metamorphosis of Gneiss to Granite
Gneiss
When gneiss melts and
cools, it becomes granite!
Granite
From Metamorphic to Igneous!
THE ROCK CYCLE
A model that sums up the formation, breakdown, and
reformation of rock
• Series of
changes that
“recycle” rocks
from one type
to another
Assignment #15: Rock or
Mineral Lab
Fossil Vocabulary (p. 30)
• Law of Superposition: Top layer is the
youngest in undisturbed layers of rocks
• Strata/Stratified/Stratification: Layer of
rocks
• Fossils: Remain or trace of living thing
• Index Fossil: Fossil remains of organism
that lived a very brief time – often found in
only one layer of rock
• Mass Extinction: Disappearance of large
number of species over short time
Fossil Vocabulary Cont.
• Relative Time: Time compared to another
time; younger or older than _____
• Resident Time: Time an element occupies
a place
• Absolute Time: Exact time – usually AD or
BC are specified
• Geologic Time Scale: Outline of major
events in Earth’s history – based upon
mass extinction periods
Homework: #19 Fossil
Vocabulary Flash Cards