Geology in the news: Representatives of the Maldives, Kiribati, the Seychelles, Palau, and other low-lying island nations are going to mount an aggressive campaign at the U.N. General Assembly when it reconvenes on Sept. 28th.

Their goal will be to get participating nations at the Paris global-warming conference in December to adopt toughtough anti-warming standards, in hopes of preserving their nations' very existence.See http://tinyurl.com/ohabjwo

This is why the HVO has placed Mauna Loa on a "yellow alert."

On a more local frontOn a more local front: : There is now a Geology Help Center – in There is now a Geology Help Center – in Mudd 411. Advanced Geology majors will be there to provide help Mudd 411. Advanced Geology majors will be there to provide help on Sundays and Tuesdays, from 7-9 p.m. On weeks with GE141 on Sundays and Tuesdays, from 7-9 p.m. On weeks with GE141 exams, they will have extra Monday shifts, also 7-9 p.m. exams, they will have extra Monday shifts, also 7-9 p.m. June Li, June Li, Oriana Battifarano, Oriana Battifarano, andand Lauren McCarthy Lauren McCarthy will be there to help! will be there to help!

Plate Tectonics RecapPlate Tectonics Recap The Earth's surface is underlain by relatively The Earth's surface is underlain by relatively

RIGIDRIGID tectonic PLATEStectonic PLATES of of lithospherelithosphere, resting , resting atop plastic, deformable atop plastic, deformable aesthenosphereaesthenosphere..

Tectonic plates Tectonic plates DIVERGEDIVERGE at extensional zones at extensional zones The process is driven by The process is driven by CONVECTIONCONVECTION in the in the

mantle, resulting in mantle, resulting in SLAB PULLSLAB PULL at subduction at subduction zones, and zones, and SLAB PUSHSLAB PUSH at areas of at areas of mantle mantle upwellingupwelling..

The The Mid-Ocean Rise and Ridge SystemMid-Ocean Rise and Ridge System ( (MORRSMORRS) ) marks the areas where marks the areas where plate divergence plate divergence is taking is taking place.place.

Flow rates are measured in cm/year (typically 2-15 Flow rates are measured in cm/year (typically 2-15 cm/yr)cm/yr)

Plate Tectonics Recap IIPlate Tectonics Recap II There are three kinds of There are three kinds of Zones of ConvergenceZones of Convergence

where tectonic plates come together.where tectonic plates come together. Oceanic subduction beneath a continental marginOceanic subduction beneath a continental margin

– e.g., western South America, or the Pacific – e.g., western South America, or the Pacific Northwest of the U.S.A., or KamchatkaNorthwest of the U.S.A., or Kamchatka

Oceanic subduction beneath other oceanic crustOceanic subduction beneath other oceanic crust, , creating an creating an island arc systemisland arc system – e.g., the Aleutian, – e.g., the Aleutian, Kuril, Japanese or Philippine Islands, as well as the Kuril, Japanese or Philippine Islands, as well as the Antilles, Sumatra & JavaAntilles, Sumatra & Java

Continent-continent collisionsContinent-continent collisions, as in India-Asia., as in India-Asia.Plate convergence is what creates most Plate convergence is what creates most

mountains – and is why major mountain mountains – and is why major mountain ranges are linear featuresranges are linear features..

Plate Tectonics Recap IIIPlate Tectonics Recap IIIHawaiiHawaii is NOT on a plate margin, but owes its is NOT on a plate margin, but owes its

origin to the Pacific Plate moving NW over a origin to the Pacific Plate moving NW over a mantle plumemantle plume, or "hot spot" that produces , or "hot spot" that produces volcanism.volcanism.

The The San Andreas FaultSan Andreas Fault of California is a of California is a transform transform faultfault, in which the North American and Pacific , in which the North American and Pacific Plates are Plates are sliding sideways past each othersliding sideways past each other. This is . This is along an offset in the East Pacific Rise, part of the along an offset in the East Pacific Rise, part of the MORRSMORRS..

Accreted terranesAccreted terranes are blocks of land that had their are blocks of land that had their own geologic history, but got "stuck onto" the own geologic history, but got "stuck onto" the continent by convergent plate motions.continent by convergent plate motions.

Moving right along ...Moving right along ...

Chemistry of the EarthChemistry of the Earthand anand an

Introduction to MineralsIntroduction to Minerals

Iron (Fe) 34.8%Oxygen (O) 29.3%Silicon (Si) 14.7%Magnesium (Mg) 11.3%Sulfur (S) 3.3%Nickel (Ni) 2.4%Calcium (Ca) 1.4%Aluminum (Al) 1.2%

NOTE that Fe is the most abundant element in the NOTE that Fe is the most abundant element in the EarthEarth as a whole!as a whole!

Only EIGHT elements make up >98% Only EIGHT elements make up >98% of the of the entire Earthentire Earth::

Oxygen O 45.2% of crust Silicon Si 27.2%Aluminum Al 8.0%Iron Fe 5.8%Calcium Ca 5.1%Magnesium Mg 2.8%Sodium Na 2.3%Potassium K 1.7%

O + Si = ~72% of the crust; SILICATE minerals are far and O + Si = ~72% of the crust; SILICATE minerals are far and away the dominant group on Earth.away the dominant group on Earth.

Quartz (Quartz (SiOSiO22) is one of the most common minerals (see fig. 3.3, ) is one of the most common minerals (see fig. 3.3,

p. 76; fig. 3.4d, p. 79; fig. 3.7a, p. 80)p. 76; fig. 3.4d, p. 79; fig. 3.7a, p. 80)

CONTINENTAL CRUSTCONTINENTAL CRUST is enriched in lighter elements is enriched in lighter elements

ELEMENTS COMBINE via chemical bondingELEMENTS COMBINE via chemical bonding a) IONIC BONDING occurs when an element gains or loses a) IONIC BONDING occurs when an element gains or loses

an electron to have a complete outer shell; this occurs when an electron to have a complete outer shell; this occurs when elements have many or very few electrons in outer shell. elements have many or very few electrons in outer shell. (e.g., K, Na, Cl)(e.g., K, Na, Cl)

Structure of halite - NaCl - Structure of halite - NaCl - showing ionic bonding at work showing ionic bonding at work

Size of elements is also a factor Size of elements is also a factor in mineral formation.in mineral formation.

Positive ions Positive ions (cations) (cations) are are usually smaller than negative usually smaller than negative ions ions (anions)(anions)..

The smaller The smaller cationscations tend to fit in tend to fit in spaces between larger spaces between larger anionsanions..

b) COVALENT BONDING occurs when elements have b) COVALENT BONDING occurs when elements have moderate numbers of electrons (e.g., Si, C, Femoderate numbers of electrons (e.g., Si, C, Fe++++++), so it's easier ), so it's easier for them to for them to share electronsshare electrons than to strip or fill an outer shell than to strip or fill an outer shell per each atom.per each atom.

Structure of ethane, a gas, Structure of ethane, a gas, showing covalent C-C and C-H showing covalent C-C and C-H

bondingbonding Water Water is also held together is also held togetherby covalent bondsby covalent bonds

Covalent bonding forms strong bonds holding minerals together.Covalent bonding forms strong bonds holding minerals together.

In metallic bonding, important in many native elements (like gold or copper), the metallic ions form a crystal lattice that is stabilized by a "sea" of electrons that are free to move from one ion to another.

These free electrons are why metals are able to convey an electrical current!

Critically important in many minerals is Critically important in many minerals is IONIC SUBSTITUTION IONIC SUBSTITUTION (the substitution (the substitution of one ion for another of similar size and of one ion for another of similar size and the same or a close electrical charge)the same or a close electrical charge)

TWO are extremely common and VERY important :TWO are extremely common and VERY important :

1.1.

This can be illustrated in the structure of the rock-forming This can be illustrated in the structure of the rock-forming mineral mineral OLIVINEOLIVINE: :

THIS pair of ions is critical - because both silicon and THIS pair of ions is critical - because both silicon and aluminum are so abundant. This characterizes aluminum are so abundant. This characterizes THE major mineral group that makes up THE major mineral group that makes up over half the entire crust - the - the feldsparsfeldspars!!

2.2.

HOWEVERHOWEVER, this also sets up a charge imbalance! , this also sets up a charge imbalance! This is accommodated by addition of KThis is accommodated by addition of K++, Na, Na++, , CaCa++++ and other ions to the minerals. and other ions to the minerals.

Soooo, what IS a mineral, anyway?Soooo, what IS a mineral, anyway?

1. Naturally occurring1. Naturally occurring

2. Inorganic solid2. Inorganic solid

3. Has a constant chemical composition, or 3. Has a constant chemical composition, or one varying within defined, set limitsone varying within defined, set limits

4. Has a crystalline (ordered) internal 4. Has a crystalline (ordered) internal structure. structure. ( ( This is reflected in the crystal form! This is reflected in the crystal form! ))

QUESTION: Is the January ice on QUESTION: Is the January ice on Johnson Pond a mineral ???Johnson Pond a mineral ???

Is wood a mineral ?Is wood a mineral ?Is glass a mineral ?Is glass a mineral ?

Critical to remember is that ALL minerals Critical to remember is that ALL minerals are stable are stable ONLYONLY under specific under specific

temperature-pressure conditions!temperature-pressure conditions!

Minerals that have both silicon and Minerals that have both silicon and oxygen in them are the oxygen in them are the silicate mineralssilicate minerals. .

These comprise These comprise 95%95% of the crust - we'll of the crust - we'll cover them last, but in some detail.cover them last, but in some detail.

The NON-silicate minerals (i.e., all the The NON-silicate minerals (i.e., all the others) are, save the carbonates, most others) are, save the carbonates, most

important for their important for their economic economic significance.significance.

1. The first group is the simplest group: 1. The first group is the simplest group: NativeNative elementselements . . These are comprised of a single element, not in combination These are comprised of a single element, not in combination with anything else.with anything else.

GoldGold

DiamondsDiamondsGraphiteGraphite

NativNative e coppecopperr

Native silverNative silver Native sulfurNative sulfur

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** will denote those you'll see in lab!will denote those you'll see in lab!

2. Second group is the 2. Second group is the SulfidesSulfides. Many are major ores. These . Many are major ores. These are comprised of a are comprised of a metalmetal plus plus sulfursulfur..

Pyrite - Pyrite - NOTNOT an ore an ore Chalcopyrite Chalcopyrite Cu Cu Bornite Bornite Cu Cu

Galena Galena Pb Pb Molybdenite Molybdenite Mo Mo

+ Cinnabar + Cinnabar Hg Hg

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*Sphalerite Sphalerite Zn …. Zn ….

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Sulfide minerals, and Native Sulfur (from coal seams) Sulfide minerals, and Native Sulfur (from coal seams)

Some of you may remember the acid mine drainage spill into the Animas River of Colorado this past summer.

3. Third group is the 3. Third group is the Oxides and HydroxidesOxides and Hydroxides. Many of these . Many of these are also major ores. These are comprised of a metal plus are also major ores. These are comprised of a metal plus either oxygen or an (OH) group, or both.either oxygen or an (OH) group, or both.

MagnetiteMagnetite HematiteHematite Limonite LimoniteThe three major ores of iron , mined worldwideThe three major ores of iron , mined worldwide

Bauxite is a blend of AlOOH, Al (OH)Bauxite is a blend of AlOOH, Al (OH)33, and other , and other

aluminum oxides and hydroxidesaluminum oxides and hydroxides A. Is Bauxite a mineral?A. Is Bauxite a mineral?B. Why is this specimen red?B. Why is this specimen red?C. For what would IT be useful?C. For what would IT be useful?

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Other important oxides include:Other important oxides include:Corundum - AlCorundum - Al22OO33

Used to be Used to be mined mined extensively for extensively for abrasives - now abrasives - now most important most important for the colored for the colored varieties …..varieties …..

Rubies ….Rubies ….

sapphiressapphires

And the And the Oriental Oriental

emeralds emeralds

All coloration is due to trace impurities ...All coloration is due to trace impurities ...

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4. The fourth group is the 4. The fourth group is the HalidesHalides - made up of a metal plus - made up of a metal plusa halogen - usually Fluorine or Chlorinea halogen - usually Fluorine or Chlorine

Halite - NaClHalite - NaCl

Sylvite - KClSylvite - KCl

Halite and Sylvite Halite and Sylvite show well the show well the influence of influence of

internal structure internal structure on the ultimate on the ultimate

shape of the shape of the mineral grains.mineral grains.

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Fluorite Fluorite - CaF- CaF22 - is also a very important halide mineral - is also a very important halide mineral

As you can As you can guess from guess from

these pictures, these pictures, fluorite can be fluorite can be

practically practically ANY color!ANY color! WHY???WHY???

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