Transcript Rock-Cycle

Rock Cycles, Rocks, Minerals,
& Resources
The Rock Cycle
The Rock Cycle
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Crystallization- Molten magma cools, and
solidifies within the Earth to produce igneous
rocks.
 Crystallization may occur either beneath the
surface or, following a volcanic eruption, at the
surface.
 If the igneous rocks are exposed at the surface,
they will undergo a process termed weathering.
The Rock Cycle Continued…
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Weathering is defined as the disintegration and
decomposition of igneous rock at or near the
surface of the Earth.
 The materials, or sediment that result are moved
down-slope by gravity before being picked up and
transported by any of a number of erosional
agents- running water, glaciers, wind, or waves.
The Rock Cycle Continued…
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Eventually these particles and dissolved
substances are deposited in the ocean, river
floodplains, desert basins, swamps, and dunes.
 Next, the sediments undergo lithification, a term
meaning “conversion into rock”.
 Sediment is usually lithified into sedimentary rock
when compacted by the weight of overlying layers
or when cemented as percolating groundwater fills
the pores with mineral matter.
The Rock Cycle Continued…
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If the resulting sedimentary rock is buried deep within the
Earth and involved in the dynamics of mountain building,
or intruded by a mass of magma, it will be subjected to
great pressures and/or intense heat.
The sedimentary rock will react to the changing
environment and turn into metamorphic rock.
When metamorphic rock is subjected to additional pressure
changes or to still higher temperatures, it will melt,
creating magma, which will eventually crystallize into
igneous rock.
Summary: The Rock Cycle
Processes driven by heat from the Earth’s interior
are responsible for creating igneous and
metamorphic rocks.
 Weathering and erosion, external processes
powered by energy from the sun, produce the
sediment from which sedimentary rocks form.
 Although rocks may seem to be unchanging
masses, the rock cycle shows that they are not.
The changes, however, take time-great amounts of
time.
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Characteristics of Minerals

Minerals are defined as naturally occurring,
inorganic crystalline solids that possess a
definite chemical structure.
 Minerals are the building blocks of rocks.
Properties of Minerals

Crystal form: The external appearance of a
mineral as determined by its internal
arrangement of atoms.
 Luster: Luster is the appearance or quality
of light reflected from the surface of a
mineral.
 Color.
Properties of Minerals
Continued…
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Streak: The color of a mineral in its
powdered form.
 Hardness: The resistance a mineral offers to
scratching.
 Cleavage: The tendency of a mineral to
break along planes of weak bonding.
Mohs Scale of Mineral
Hardness
Mineral Groups
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Minerals can be classified into groups
depending upon their chemical composition.
Relative Abundance Of The
Most Common Elements In
The Earth’s Crust
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Oxygen (O) 46.6%, Silicon (Si) 27.7%,
Aluminum (Al) 8.1%, Iron (Fe) 5.0%, Calcium
(Ca) 3.6%, Sodium (Na) 2.8%, Potassium (K)
2.6%, Magnesium (Mg) 2.1%, All others 1.7%.
Mineral Groups Continued…
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The largest group of rock forming minerals is the
silicate group.
 All silicate minerals contain silicon and oxygen.
 Some examples of silicate minerals are olivine,
augite hornblende, garnet, biotite, albite, and
quartz.
 Silicates are the most common minerals because
most of the Earth’s crust is made of silicon and
oxygen.
Mineral Groups Continued…
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Non-silicate minerals are those that do not
contain silicon and oxygen.
 There are five groups of non-silicates:
oxides, sulfides, halides, carbonates and
sulfates.
Mineral Groups Continued…
Oxides

Oxides are minerals that form when an
element combines with oxygen.
 Some examples of oxides are corundum,
hematite, and magnetite.
Mineral Groups Continued…
Sulfides

Sulfides are minerals that form from
compounds that contain sulfur.
 Some examples of sulfides are galena and
pyrite.
Mineral Groups Continued…
Halides

Halides are minerals that form when certain
elements combine with the Halogen Group
from the periodic table.
 The halogen group includes chlorine,
bromine, fluorine, and iodine.
 Some examples of halides are halite and
fluorite.
Mineral Groups Continued…
Carbonates
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Carbonates are minerals that contain a
carbon atom surrounded by three oxygen
atoms (carbonate ion).
 Some minerals that contain this ion are
azurite, aragonite, and malachite.
Mineral Groups Continued…
Sulfates
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Sulfates are minerals that contain a sulfur
atom surrounded by four oxygen atoms
(sulfate ion).
 Some minerals that contain this ion are
gypsum, celestite, and barite.
Mineral Resources
Mineral resources are the Earth’s storehouse of
useful minerals that can be recovered for use.
 Resources include already identified deposits from
which minerals can be extracted profitably, called
reserves, as well as well known deposits that are
not yet recoverable under present economic
conditions or technology.
 Deposits inferred to exist, but not yet discovered,
are also considered as mineral resources.
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Mineral Resources Continued…
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There three principal categories for mineral uses
are: rock forming, economic, gems and
ornamentals.
 Rock forming refers to the primary function or use
of some minerals.
 Many minerals have commercial or economic use.
Some minerals are considered ore minerals (e.g.
hematite – iron ore), while others are common
commercial products (e.g. calcite – cement).
Mineral Resources Continued…
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Common gemstones used in jewelry are
actually minerals. Examples are diamonds,
garnet, and amethyst.
 Large mineral specimens can also be used
for decorative or ornamental purposes.
Examples are pyrite (fool’s gold), or geodes
lined with quartz or amethyst crystals.
Mineral Resources Continued…
Recall that more than 98% of the Earth’s
crust is composed of only eight elements.
 Except for oxygen and silicon, all other
elements make up a relatively small fraction
of common crustal rocks. Indeed, the
natural concentrations of many elements are
exceedingly small.
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Mineral Resources Continued…
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A deposit containing only the average
crustal percentage of a valuable element
like gold is worthless if the cost of
extracting it greatly exceeds the value of the
material recovered.
 To be considered of value, an element must
be concentrated above the level of its
average crustal abundance.
Mineral Resources Continued…
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Examples of minerals and their economic
use: Hematite (oxides) ore of iron, Galena
(sulfides) ore of lead, Gypsum (sulfates)
plaster, Gold (native elements) trade and
jewelry, Fluorite (halides) used in steel
making, and Calcite (carbonates) Portland
cement and lime.
Works Cited
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1.) The Mineral Gallery
 http://minerals.galleries.com/default.html
 2.) Minerals
 http://www.tulane.edu/~sanelson/geol111/m
inerals.html
 3.) Rock Cycle Images
http://rst.gsfc.nasa.gov/Sect2/Sect2_1a.html
Works Cited Continued…
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4.) Tarbuck, Edward J., Lutgens, Frederick
K. Earth Science 8th Ed. 1997 New Jersey:
Prentice Hall Inc.
 5.) Image- silicon-oxygen tetrahedron
http://www.msdwc.k12.in.us/msdclass/WE
NJ