geoscience exam I

native minerals

made of single element

6 properties of minerals

1. solid

2. naturally occurring

3. inorganic

4. defined (but not fixed) chemical composition

5. made up of one or more elements

6. crystalline structure

octet rule

atoms tend to gain, lose, or share electrons to achieve a stable configuration of eight valence electrons in their outermost shell

metallic bonds

electrons move around freely between atoms resulting in high electrical and thermal conductivity, malleability, metallic luster

covalent bonds

electrons are shared between two atoms to achieve electrical neutrality (Cl2, H2)

ionic bonds

electrons transfered from one to another (NaCL, KCl)

chemical bonds

the transfer or sharing of electrons that results in full valence shell

ions formed when…

one atom loses or gains valence electrons (cation+ and anion- respectively)

elements are defined by…

# of protons which determines their chemical nature

assimilation

xenoliths fall into magma due to magma dissolving rock wall it asses through

variation in magma due to…

1. inital rock source composition

2. partial melting (fractional chrystallization)

3. assimilation

4. magma mixing

is mercury a mineral?

considered mineraloid because liquid state lacks crystalline structure

crystal shapes

1. cubic (halite)

2. octahedral (diamond)

3. hexagonal (quartz)

4. dodecahedra (garnet)

5. orthorhombic (stibite)

6. rhombohedra (calcite)

7. columnar (kyanite)

minerals have symmetry such as…

mirror images and rotation about an axis that can be used for identification

5 ways crystals can form:

1. solidification from melt

2. precipitate from solution

3. solid-state diffusion (rock metamorphosis)

4. biomineralization

5. precipitate from gas

continental crust is mostly

O (46.6%), Si (27.7%), Al (8.8%), Fe (5.0%), Ca, Na, K, Mg which make up majority of rock-forming minerals

two mineral groups

silicates, non-silicates

silicate minerals

most common, >90% Earth’s crust, SiO4^-4 tetrahedron = building blocks for minerals

non-silicate minerals

important economically, more rare 8%, and classified by dominant anion

carbonates (CO3)^-2, road aggregate, cement, building stone, fizz w/ HCI

sulfates (SO4)^-2 plaster

halides (F-, Cl-, Br-, I-) table salt

sulfide (S)^-2

oxides O^-2, iron ore

crystalline structure

atoms arranged in specific order (crystal lattice)

glass

solid with disordered atoms, amorph, NOT MINERAL

silica tetrahedron

• 4 O atoms around much smaller Si

• isolated, single/double chains, sheets, framework

silicate groups

1. feldspar (framework)

• plagioclase

• K-feldspar

2. pyroxene (1 chain)

• augite

3. amphibole (2 chain)

• hornblende

4. quartz (framework)

5. mica + clay (sheet)

• muscovite, biotite

6. olivine, garnet (isolated)

rock cycle

origin of igneous, sedimentary, and metamorphic rocks; how they can all transform into another

• crust + upper mantle melts —> magma, less dense magma rise —> erupts at surface + cools

lithification

sediment compacted + cemented to form sedimentary rock

2 types of igneous

1. plutonic (intrusive)

2. volcanic (extrusive)

metamorphism

sedimentary rock buried deep in crust, intense heat + pressure changes it to metamorphic

weathering

breaks down rock, transported + deposited as sediment

crystalization

magma or lava cools and solidifies, forming igneous

melting

magma forms by rock melting deep under surface

5 rock cycle processes

1. crystallization

2. weathering

3. lithification

4. metamorphism

5. melting

why does magma form?

partial melting of crust + upper mantle caused by heat transfer, volatile addition, pressure release

geothermal gradient

directly proportional relationship btwn temp and depth

upper crust: 30C/km

volatiles

gas content, commonly H20 and CO2 brought into subduction zones melting overlying asthenosphere by lowering melting point

what is magma made of?

solid (mineral crystals in melt)

liquid (mobile ions Si and O primarily)

gas

types of magma

1. felsic (crustal)

2. intermediate (crustal)

3. mafic/ultra-mafic (mantle, crustal source)

4 reasons for variation in magma composition

1. fractional crystallization/partial melting (felsic —> mafic)

2. initial rock source composition (mantle vs crustal)

3. assimilation

4. magma mixing

how/why does magma move?

• less dense than surround rock + more buoyant, rises

• overlying rock puts pressure, rises

• viscosity, less viscous more movement

viscosity

resistance to flow dependent on temp, volatile content, and silica content

• felsic, higher v + inverse

• cooler, higher v + inverse

• less volatiles, higher v + inverse

latitude vs longitude

lat

• horizontal parallel lines to equator N(+), S(-)

• 360 degrees

• small circles

long

• vertical line to prime meridian, not parallel spacing closer at poles E(+), W(-)

• great circles

3 major map projection types

1. cylindrical

2. planar

3. conic

Datun

ellipsoid reference surface with spherical or cartesian co-ord system; tells us lat + long of set point on elliosoid

Earth system components

1. atmosphere

2. geosphere

3. hydrosphere

4. biosphere

5. crysphere

geologists study…

1. solid Earth + processes (earthquakes, tectonics…)

2. environment (atmosphere, weather, climate)

3. planetary (Earth + solar system)

4. economy (oil, gas, minerals, soil, water

earth system

internal + external heat engines (heat —> mechanical energy)

internal heat engine

convection- hot buoyant material moving upward, cool dense surface downward

earth layers

1. oceanic/continental crust

2. uppermost mantle

3. asthenosphere

4. core

mantle = asthenosphere + uppermost

lithosphere = uppermost mantle + crust

oceanic vs continental crust

oceanic- underlies ocean

• thin, basalt composition

continental

• thick, granite

mantle

• 80% Earth’s volume

• denser rock (Fe, Mg)

• flowing solid rock

core

• innermost, densest, inner (solid), outer (liquid), metal (Fe, Ni), magnetic field

plate tectonics

a theory that Earth’s surface is divided into a few large thick plates that are moving slowly and changing in size; intense activity at boundaries

continental drift

earlier hypothesis before plate tectonics

divergent boundary

boundary separating 2 plates moving away from eachother

• mid ocean ridges

• continent drifts + thins —> valley —> touches magma chamber —> erupts continuously forming oceanic crust

• forms oceans

convergent boundaries

two plates towards eachother

• ocean-continent- continental plate overlaps ocean (less dense, more buoyant), ocean sinks along subduction zone + melts, forms mountain belts

• ocean-ocean- forms volcanic island arc as more dense plate sinks + volcano forms from ocean floor

• continent-continent- neither plate subducts, vertical uplift, forms very high mountains

subduction zone

elongate region where denser tectonic plate slides beneath less dense plate, sinking into mantle

transform boundary

slide past eachother horizontally

• typically mid oceanic ridges

• causes faults + earthquakes

isostaric adjustment

vertical movement of sections of crust to achieve balance/equilibrium

• continental crust rising over oceanic

• granite breaking down to clay (via erosion)

• lithification

age of Earth

4.6Ga