Transcript Rocks - Schoolwires

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NCSCOS:
EEn.2.1.1 Explain how the rock cycle, plate
tectonics, volcanoes, and earthquakes impact
the lithosphere
E.Q. - How rock formation is depicted using
Rock Cycle Diagrams.
E.Q. - What are the mechanisms that drive
the Rock Cycle.
The diagram in the next slide represents the ROCK
CYCLE—a “Concept Map” that represents the
processes of continuous changes that connect the
three major groups of rocks:
IGNEOUS
SEDIMENTARY
METAMORPHIC
It also shows two other important parts of the
“Rock Cycle” – SEDIMENTS and Molten LAVA /
MAGMA
Weathering of Rock is also an major process of the
“Rock Cycle”
lithosphere ( Greek [lithos]
for "rocky" + [sphaira] for
"sphere") is the rigid outermost
shell of a rocky planet. On Earth,
it comprises the crust and the
portion of the upper mantle that
behaves elastically on time scales
of thousands of years or greater.
 The
Diagenesis
Rock Cycle
Lithification
Sedimentary rocks may be made of rock fragments—
sediments—or by chemical reactions. The classification of
sediments is shown below.
Diagenesis
In geology, diagenesis is any and all chemical,
physical, and/or biological change(s) undergone
by sediments to form sedimentary rock, it does
not include weathering and metamorphism at
the surface. These changes happen at relatively
low and moderate temperatures and pressures
and result in changes to the rock's original
composition and texture. There is no sharp
boundary between diagenesis and
metamorphism, but metaporphism occurs at
much higher temperatures and pressures.
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LITHIFICATION (from the Greek word lithos
meaning 'rock‘) is the process in which sediments
compact under moderate pressure, expel fluids,
and gradually become solid sedimentary rock.
Essentially, lithification is a process of porosity
destruction through compaction and cementation.
Lithification includes all the processes which
convert unconsolidated sediments into
sedimentary rock.
Coal Formation
Coal begins as layers of large masses ofplant matter
accumulating at the bottom of a body of water. For
the process to continue, the plant matter must be
protected from biodegradation and oxidation, usually
by mud or acidic water. This traps their carbon in
immense peat bogs that are eventually covered over
and deeply buried by sediments. Under this
compression the plant material is changed into coal:
over time, the chemical and physical properties of
the plant remains are changed by geological action,
diagenesis to create a solid material.
 Petrification,
though often used
as a synonym, is more
specifically used to describe
the replacement of organic
(from living) material by
silicates in the formation of
fosslis.
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The most important of
these is COAL.
Anthracite coal results
from the greatest
pressure and releases
the most energy when
burned. Other varieties
are bituminous and
lignite. “Petrified”
(permineralized) wood
is another organic
rock.
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Shale is the most
common
sedimentary rock
Sedimentary rocks
cover about threequarters of the land
surface
For more about
sedimentary rocks:
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks1.html
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Form by solidification (crystallization) of
melted minerals
At the surface, LAVA hardens quickly to form
EXTRUSIVE ROCKS with tiny (FINE-GRAINED)
crystals or GLASSY (no crystal) TEXTURES
Beneath the surface, MAGMA slowly hardens
to form INTRUSIVE ROCKS with easily visible
(COARSE-GRAINED) crystal texture.
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Light-colored,
coarse- grained, no
pattern
Mostly quartz,
feldspar, mica, and
hornblende
Often used for
buildings and
monuments
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Dark-colored, finegrained, extrusive
Formed where lava
erupted onto surface
Most widespread
igneous rocks
Found locally in the
Palisades along west
shore of Hudson River,
Connecticut River
valley
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Dark-colored,
coarse- grained
intrusive
Similar composition
to basalt—
plagioclase feldspar
with some
pyroxene and
olivine
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Natural volcanic glass
Forms when lava cools
very, very quickly
Usually dark, but small
pieces may be clear
Fractures along curved
(conchoidal) surface
Used as spear and
arrow points, knives
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Light colored,
frothy (many air
spaces)
For more about igneous rocks:
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Same minerals as in
granite, but finer in
grain size
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Formed by EXTREME HEAT AND PRESSURE
changing existing rocks
REGIONAL METAMORPHIC affects a large area
and results from plate tectonics
CONTACT METAMORPHISM affects rocks on a
local scale, such as “baking” sedimentary
rocks next to magma or lava
Is usually indicative of Hydrothermal Activity