Transcript Minerals can be identified by their properties

PLATE TECTONICS
ROCKY CYCLE, MINERALS,
VOLCANOES, & EARTHQUAKES
Integrated Science
Minerals can be identified by their
properties
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A mineral is a naturally occurring, solid substance made
up of a single element or compound.
Examples Halite (table salt), copper, gold, and silver.
All minerals are inorganic—they are never formed by
living or once living things.
Minerals have crystalline structures that reflect the
orderly arrangement of their atoms.
Minerals can be identified by their
properties
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Geologists classify minerals into different groups.
The classification is based upon their chemical
composition (which elements are present) and their
crystalline structure (how the elements are arranged).
It is often easy to identify and classify minerals by
observing their physical properties, (crystal form,
hardness, cleavage, luster, color, streak, and specific
gravity).
Minerals can be identified by their
properties
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Crystal Form
The orderly arrangement of atoms in a crystal
Fool’s gold (iron pyrite) you can see the cubes, quartz has 6
sided prisms that end in a point, asbestos is in threadlike
fibers, hematite has globular shapes that looks like grapes
Well shaped crystals are rare in nature because the
crystals must grow in cramped spaces.
Minerals can be identified by their
properties
Minerals can be identified by their
properties
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Sometimes two or more minerals come from the same
elements in the same proportions but they are arranged
differently, these are called polymorphs.
Graphite and Diamond are polymorphs made of carbon,
because of the different arrangement both have vastly
different properties.
The formation depends upon the particular temperatures
and pressures, this makes them good indictors of the
geologic conditions at their formation sites.
Minerals can be identified by their
properties
Minerals can be identified by their
properties
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Hardness is the Resistance of a Mineral to Scratching
Diamonds can scratch glass because it is harder than
the glass.
The harder mineral will always scratch the softer one.
Hardness depends on the strength of a minerals’
chemical bonds—the stronger the bonds the harder the
mineral
Minerals can be identified by their
properties
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Factors that influence bond strength are ionic charge, atom or
ion size, and packing.
Strong bonds generally occur between charge ions (ionic
bonding) the greater the attraction the stronger the bond.
Size affects strength because small atoms and ions can generally
pack closer together than large atoms and ions.
Closely packed atoms and ions have a smaller distance between
them and are attracted to each other with more force.
Gold with large atoms is soft, while diamond with small carbon
atoms is hard.
Minerals can be identified by their
properties
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Cleavage and Fracture are ways in which minerals break
Cleavage is the property of a mineral to break along
planes of weakness (determined by crystal structure and
chemical bond strength)
Muscovite (mica) has perfect cleavage in one direction, it
will break into thin sheets
Calcite has cleavage in 3 directions, it breaks to form
rhombohedral faces.
Garnet has no cleavage (strong bonds in all directions)
Minerals can be identified by their
properties
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Fracture is when a mineral breaks but not along a
cleavage plane.
A fracture that is smooth and curved so that it
resembles broken glass is called conchoidal.
Most minerals fracture irregularly.
Minerals can be identified by their
properties
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Luster of a mineral is the way its surface when it reflects
light
Minerals of the same color may have different lusters,
and minerals of the same luster may different colors.
Adamantine - very gemmy crystals
Dull - just a non-reflective surface of any kind
Earthy - the look of dirt or dried mud
Fibrous - the look of fibers
Greasy - the look of grease
Gumdrop - the look a sucked on hard candy
Metallic - the look of metals
Pearly - the look of a pearl
Pitchy - the look of tar
Resinous - the look of resins such as dried glue or chewing gum
Silky - the look of silk, similar to fibrous but more compact
Submetallic - a poor metallic luster, opaque but reflecting little light
Vitreous - the most common luster, it simply means the look of glass
Waxy - the look of wax
Minerals can be identified by
their properties
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A minerals color is easily observable feature, it is not very
reliable means of identification.
Some minerals such as copper and turquoise have a distinct
color.
The majority of minerals can be occur in a variety of colors
or can be colorless.
Chemical impurities can affect a mineral’s color
The mineral corundum gives us red rubies or blue sapphires
depending upon the impurities in it.
Minerals can be identified by
their properties
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Streak is the name given to the color of a mineral in its powdered
form.
This is a very important characteristic of identifying minerals have
a metallic or semimetallic luster.
The streak test- when rubbed across an unglazed porcelain plate,
all minerals leave behind a thin layer of powder—a streak.
The streak of a mineral is always the same color, no matter the
color variance of the mineral
A white streak (nonmetallic luster)cannot be used to identify
minerals.
Minerals can be identified by
their properties
Specific Gravity
 Density = Mass / Volume (how heavy a mineral
feels for its size)
 Specific Gravity = Density of mineral / Density of
Water
 Gold has specific gravity of 19.3 This allows
miners to pan for gold.
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Minerals can be identified by
their properties
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Chemical Properties
Two simple tests are the taste test and the
acid test (fizz test—Carbon dioxide CO2)
The taste test is used to identify halite
(common table salt) Do not taste test
minerals some are poisonous!!
Carbonate minerals will fizz when dilute
(low concentrations) of hydrochloric acid
(HCl) are place on them
On the way to Rocks
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Rocks are made of many different minerals
Minerals are formed from the process of crystallization
(growth of a material whose atoms come together in a
specific chemical composition and crystalline
arrangements)
Crystallization of minerals comes from 2 different
sources magma (igneous rock) and water solutions
(sedimentary rock)
On the way to Rocks
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Melting point and Freezing point are the
same temp!
Minerals melt at about 750oC to 1000oC
The Earth’s temp increases about 30oC for
every km.
When minerals & rock melt new magma is
produced, when magma cools minerals
form and new rock is produced.
On the way to Rocks
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Partial melting occurs because rocks are made of
many minerals. The lower melting point minerals
melt first.
If the whole rock melts the magma has the same
chemical composition as the original rock.
Because of the different minerals that end up in the
magma it then will cool into different rock types.
On the way to Rocks
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Crystallization also occurs in water solutions.
Chemical sediments are formed when minerals precipitate form water in
they were dissolved.
There are 2 categories: carbonates and evaporites
Limestone is the most abundant carbonate rock, it forms when organisms
with shells die they accumulate at the bottom of the sea floor, through
compaction over time limestone forms.
Cave dripstones (stalactites & stalagmites) also form from precipitating
sediment from dripping water
Evaporites are formed when a restricted body of salty lake water
evaporates. Gypsum and halite are form this way.
Rocks are divided into 3 Main Groups
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Many rocks are either created, changed, or
destroyed at plate boundaries.
Igneous rock formed by the cooling and
crystallization of hot molten rock called magma.
(Igneous means formed by fire)
Igneous rock makes up 95% of the Earth’s crust,
Basalt and Granite are common igneous rocks.
Rocks are divided into 3 Main Groups
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Sedimentary rocksare formed from pieces of
other rocks (sediments) carried by water, wind, or
ice. Sedimentary rocks are the most common rocks
in the uppermost part of the Earth’s crust.
In fact sedimentary rocks cover more than 2/3 of
the Earth’s surface, Sandstone, shale and limestone
are common sedimentary rocks
Rocks are divided into 3 Main Groups
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Metamorphic rockare formed from older preexisting rocks (igneous, sedimentary, or
metamorphic) that are transformed by high
temperature, high pressure, or both WITHOUT
melting.
The word metamorphic means “changed in form”
Marble and slate are common metamorphic rocks.
Rocks are divided into 3 Main Groups
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Igneous rock forms when magma cools
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Most of the continents are made of granite
Basalt is the most common on ocean floors
Extrusive (means pushed out of)igneous rock forms at the
surface of the Earth
Partial melting and crystallization produce a variety of
magma types (different amounts of silicon they contain)
The higher the silicon content the magma flows more slowly.
Temperature also affects the ability to flow of magma
Rocks are divided into 3 Main Groups
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Magma on the surface is called lava
Lava can come from cracks and fractures in the
Earth’s surface or volcanoes.
Most fissure eruptions occur when fast-flowing
basaltic lava erupts at the bottom of the ocean
forming the ocean floor.
Volcanoes come in a Variety of Shapes
and sizes
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All volcanoes are basically vents or holes where magma can
rise to the Earth’s surface
Shield volcanoes have gently sloping cones that resemble a
shield
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They are built from many lava flows that pour out in all directions
to cool as thin, gently sloping sheets
Some of the largest volcanoes in the world are shield volcanoes
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Mauna Loa in Hawaii stands 4145 meters (13,599 ft) above sea level
and more than 6750 meters (22,146 ft) above the deep ocean floor
Volcanoes come in a Variety of Shapes
and sizes
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Cinder cones
Earthquakes Make Seismic Wave
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All earthquakes create waves that travel through the Earth’s
interior.
Earthquake generated waves are called seismic waves. The way
these waves travel provides scientists with a view into the Earth’s
interior.
The major layers of the Earth the crust, mantle, outer core, and
inner core.
A wave’s speed depends on the medium through which it travels.
Example Sound waves travels faster through water than through
air.
Earthquakes Make Seismic Wave
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The speed of seismic waves depends upon the elasticity
of the material through which they are traveling
Energy is released in an earthquake and radiates in all
directions. This energy travels to the surface in the form
of seismic waves.
Seismic waves cause the ground to shake and move.
This movement is recorded on a machine called a
seismograph.
2 Types of
Seismic Waves
Surface Waves
Body Waves
Primary Waves
(P Waves)
Like Sound Waves are Longitudinal—they compress and
expand the rock they move thru
They move out in all directions
Fastest seismic waves
Travel thru any material
Secondary
Waves
(S Waves)
Transverse Wave, they vibrate
particles up & down and side to side
Slower than P waves
Cannot pass thru fluids
Rayleigh Waves
Love Waves
Move in an Up and Down
Motion
Move slower than P & S
Waves
Move in a side to side
motion
Move slower than P & S
Waves
Animations for Plate tectonics
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http://education.sdsc.edu/optiputer/teachers/oceanfloordynamics.html
Sedimentary Rocks
• 2 kinds of weathering produce sediment
• Mechanical weathering physically breaks rocks
into sediments
• Chemical weathering consists of chemical
reactions that involve water and decompose rock
into smaller pieces.
• As rock is weathered it erodes (which means it is
transported by water, wind, or ice)
Sedimentary Rocks
• Clastic sediment is small fragments of other rocks (are
usually very jagged until they are transported and
break when they collide with other rocks or fragments)
• Chemical sediment is produced by chemical means
• Glaciers usually deposit poorly sorted sediments while
wind is usually very well sorted and fine grained.
Sedimentary Rocks
• In sedimentation, sediment particles are
deposited one layer at a time it then becomes
rock thru compaction and cementation
• Minerals dissolved in water is what acts as the
cement that bonds the sediments together
• Iron oxide will produce red or orange rocks
• Limestone is formed by the precipitation of
calcium carbonate
http://www.uwgb.edu/dutchs/PLANETS/earth.htm
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Overview of Earth Systems
The three main components of the Earth
are the atmosphere, its gaseous envelope,
the hydrosphere, the surface coating of
water, and of course, the solid earth. All
three are subdivided into subsystems. The
atmosphere and hydrosphere get their
energy mostly from the Sun, and the solid
earth gets its energy from internal heat,
some of which is produced by radioactive
decay and some is left over from the
formation of the earth. A tiny amount of
energy also comes from gravitational
interactions between the Earth, the Moon,
and the Sun.
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Convection is the transportation of
heat by moving hot or cold material
from place to place. Convection
works because warm material is light
and rises, while cool material is
denser and sinks. As long as there is
a temperature difference with depth,
there will be a cycle of rising and
sinking material. A lava lamp is a
perfect illustration of convection - if
geophysicists, astronomers, and other
scientists who teach about convection
had their way, lava lamps would
never go out of style.
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In reality, there is a continuous
cycle. Material at the base of
the mantle becomes hot and
rises. As it rises, it expands
and cools, and near the
surface, heat leaks through
the crust and escapes. Cooled
mantle material begins sinking
and descends to the bottom
of the mantle, to be heated
again.