Geology intro

Introduction:
-Minerals are made of atoms (first discovered 15k years ago)
-Democritus: an Atomist
-An Atom: In the middle contains protrons (+) and neutrons (o), orbiting them are electrons (-)
-Number of protons = the atomic number (it decides what the element is, its characteristics, etc)
-2 ways to change the atomic number: 1)nuclear fusion: Happens in the sun 2) Nuclear fission: breaking it down
-# of protons = # of electrons
-electrons have layers called shells--1st shell holds 2 electrons, 2nd hold 8, 3rd hold 8, 4th holds 18
-every electrons wants a full outer shells, so it will give or take electrons
-Ion: an atom that either gave or took electrons
-Cation: an atom that has a positive charge, as it gave away electrons (meaning more protons than electons) ex. sodium Na +1 is a cation.
-Anion: Negatively charged atom, as it took for electrons. ex. Chloride Cl becomes -1.
-Positive and negatives attracts thus Na +1 and CL -1 will stick together to form NaCl with a charge of 0. This kind of bond is known as ionic bond.
-Covalent bond is when atoms share an electron to complete its outer shell, this bond is stronger than ionic bond

Surface of the Earth is mostly made of these 8 elements:
1) S (silicone)
2) Fe (iron)
3) K (potassium)
4) Na (sodium)
5) O (oxygen)
6) Mg (Magnesium)
7) Al (Aluminum)
8) Ca (Calcium)

5 requirements to be considered a mineral:
1) Naturally occurring
2) crystalline
3) Solid
4) Inorganic
5) Specific Chemical composition

What is a rock? A coherent aggregate of one or more minerals.

Characteristics of a rock:
color- not a good indication
cleavage- breakage along the weak bonds, shiny flat surface, either none or 1/2/3/4 and 90/not 90
streak- color in its powered form
Hardness- resistance of mineral to scratching. Mohs is one of the founding fathers of Geology, ranked hardness minerals from 1 to 10, called it Moh's hardness scale.
Specific gravity: the heft of the mineral, either L/M/H
Luster- how light refracts on its surface, either metallic/non-metallic
Crystal form- whole crystal or not, either cleavage fragment/fractured fragment/ or none aka. aggregate

How minerals form (3 ways):
1- precipitation: formation of a solid from a solution (= ions dissolved in water)
2- solid state reaction (oxydation/rusting)
3 - freezing (of magma)

when magma (hot soup of the 8 elements) cools it forms:
@ 1100 C = Olivine -> Pyroxene (augite) -> Amphibole (Hornblende) -> Micas -> @ 700 Quartz

K +1, Na +1, O-2, Ca +2. Fe, Mg +2, Al +3, Si +4

Si attracts 4 O's because of its charge. Any minerals with SiO4 is olivine , also can contain Mg and Fe

Mineral: Olivine -> Augite -> Hornblende -> Mica -> Quartz
Tetrahedron: Isolated -> Chain silicate-> Double chain silicate ->sheet silicate -> Framswork
formula:SiO4 -> SiO3 -> Si4O11->SiO5---------------->SiO5----------->SiO2
Charge:-4 -> -2 -> 1.5 -> -1 -> 0

= Bowen's reaction series (discontinuous)
&

Continuous:
-when augite forms, feldspars also form. 1st is calcium rich plagioclase to balanced calcium/sodium to sodium rich plagioclase.
-Orthoclase and muscovite in forms too

Ultra-mafic : green. High melting point
Mafic( from Magnesium + iron): dark.
Intermediate: gray
Felsic (from feldspare + Silica): Pink, Light

Igneous rocks:
-Formed with Magma freezes.
two types: Phaneritic and Aphanitic

Phaneritic: formed inside the earth in a pluton, has larger crystals, cools slowly, crystals seen through naked eye. Formed from Magma = intrusive

Aphanetic: formed above the ground (volcanic rock), smaller crystals, cools quickly. Formed from lava = Extrusive

Porphyritic: Large and small crystals, cools underground then goes up in the surface

Pegmatitic: Huge crystals, H2O flows in magma

Glassy: Forms so quick that no crystals form (Obsidian)
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TYPE-------------------Phaneritic----------------Aphaneritic
Ultramafic-------------Peridotite-----------------Komatiite
Mafic------------------Gabbro--------------------Basalt
Intermediate----------Diorite---------------------Andesite
Felsic------------------Granite-------------------Rhyolite

Outliers:
Dacite- Andesite with quartz ( quartz is usually in granite only)
Dunite- Peridotite with sugarly texture (all olivine)
Syenite- Granite without quartz (less than 5% quartz)
Tuff- Volcanic ash, tiny obsidian droplets, not compositionally a rock
Welded Tuff- Compressed volcanic ash
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Rock Cycle

1- magma
2- cools and forms igneous rocks
3- weathered away through mechanical weathering or chemicals weather forming clasts and solutions.
4a- Clasts goes through lithifications and becomes clastic sedimental rocks
4b- solutions precipitates and become chemical sedimentary rocks (like salt)
5- goes through heat and pressure to become metamorphic rocks (solid state reaction)
6- Melts and goes back to Magma

* The cycle does not go in order, can skip around

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Sedimentary rocks:
Weathering= when rocks break apart to sediments
Erosion= sediments travel gets deposited in a basin, and lithifies and glues together to become a sedimentary rock.

-fossils in sedimentary rocks

Ways of mechanical weathering (5):
1- jointing breaking of rocks through cracks (ie exfoliation, removing outer layer through jointing)
2- frost wedging/ salt wedging: water/salt freezing in the cracks at night then melts in the day
3 - root wedging: tree roots breaking through the rocks
4 - thermal expansion: heat from the sun expanding rocks with heat and contracting them at night
5- abrasion: stream tumbling and glaciers

Chemical Weathering (4):
1- Disolution: solution break down the rock. (i.e. coal burning create carbon dioxide in air, thus acid rain--sulfuric rain--will react with limstone, burning it)
2- oxidation: oxygen + metal = rust (statue of liberty, grand canyon 10 to 15 mil years old red of canyon is rusty iron aka hematite)
3- hydrolysis: Acidic water (all water is acidic) H2O breakdown. Granite is easy to break down.
4- Hydration: Absorption of H2O, clay minerals, very sticky, greases up.

Goldich's stability series= same order as Bowen's reaction series with olivine being the least stable of holding its shape and quartz is the most resistant.

Precipitation: non-biological and biological----
Non-bio
1- Halite (salt) 2- Calcite 3- gypsum (biggest crysals)
Bio
1- Calcite (shells) 2- chalcedony (aka quartz) 3 types 1 - agate (has layers) 2 - Japser (red) flint (black)


Steno's laws:
Original horizontality: if sediments are deposits in basin they always lay horizontally. If not then they were disrupted by earthquakes.* this rule does not apply with area of earthquakes
Law of superposition: the bottom rocks are older than the top
Lateral continuality: same type of rocks will be found in the coast from north to south


Lithification: steps= 1 compactions then 2 cementation(glue like quartz to hold together calcite)

Gravel: more than 2mm
Sand: 2mm to 1/16mm
Silt: 1/16 to 1/256
Shale: 1/256 and beyond (striated, can be parted)

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Metamorphic rocks:

Heat and pressure
Pressure increases 1k bars every 3.3 km in depth (1 bar - atm)
Geothermal gradient- temperature increases 24 C every km in depth

prograde metamorphism= more heat and pressure creates a new rock

2 types of metamorphic rocks:

1-contact--low pressure and high heat. non foliated. formed around the pluton
2- regional--high p, high h. foliated

Contact:
Hornsfel- from mafic rocks
Quarzite- from quartz
Marble- from limestone has cleavage
skarn- from limestone "xmas tree rock"
serpentine- from peridotite, looks like serpent skin

regional:
slate into phylite, into shist (sub shist- garnet, staurlite, soapstone) into gneiss, then megatite, to magma.