EXAM 1 MATERIAL Flashcards
fwhat are considered to be the building blocks of the solid earth?
chondrules
how old is the oldest rock found on earth?
4Ga
what elements are created during Big bang nucleosynthesis?
H-Li
when did the big bang occur?
13.7 Ga
what elements are created during Stellar nucleosynthesis?
Li to Fe
what elements are created during supernovae nucleosynthesis?
all elements heavier than Fe
define nebular theory
dispersed matter forms a gravitational field which condenses to form a nebula
what is the critical mass required for fusion to begin?
about 80 times the mass of Jupiter
what elements are created during supernovae nucleosynthesis?
all elements heavier than Fe
what causes nebulae to organize?
Gravitational attraction
what chemical reaction occurs in stars?
Nuclear Fusion
what elements are involved in nuclear fusion
Hydrogen used
helium produced
what is the most common element in the universe
Hydrogen
what is an accretionary disk?
gaseous mass flattens as a result of gravitational attraction
where do stars form?
at the center of accretionary disks
why are meteorites important?
meteor impacts led to the accretion of the earth
what are meteorites?
natural fragments from asteroids that impact the earth surface
where do most asteroids originate from?
the asteroid belt
where is the asteroid belt located
between mars and Jupiter
what are differentiated meteorites?
meteorites having an iron core and a rock mantle
what are undifferentiated meteorites?
these contain mm sized chondrites
what type of meteorites are more common?:
- differentiated
- undifferentiated
undifferentiated
where is the only known occurrence of chondrules?
meteorites
what type of meteorites do chondrites come from?
undifferentiated meteorites
why are chondrites important
they can be used to estimate the bulk composition of the earth
what is considered the age of the earth?
4.54Ga
how old is the earth?
4.56 Ga
how did the moon form?
a Mars-sized body is thought to have collided with the earth, the material dislodged compacted to form our moon
what evidence is there to support the theory of the moons formation?
- isotopic ratios of earth and moon match
- rocks/minerals are the same on both earth and moon
how is heat transferred within the earth?
through the lithosphere via conduction
what are the eight major tectonic plates?
- African
- Antarctician
- Australian
- Eurasian
- Indian
- North American
-South American - Pacific
what are the three types of plate boundaries?
- convergent
- divergent
- transform
describe what happens at a divergent plate margin
continental blocks separate
new crust is created
pillow basalts from
describe what happens at a convergent plate margin
two plates collide, one is subducted and destroyed
describe what happens at a transform plate margin
plates slide past one another. no new rock created
what is a mineral?
naturally occurring solids with ordered atomic structure and a definite, but not fixed chemical composition
how are minerals named?
mainly subject to the discoverer
NOT a scientific process
define the term euhedral
well-formed crystal. very uncommon
define the term subhedral
some well formed crystal faces are present
define the term anhedral
no well formed crystal faces
what is a vug?
a cavity inside a rock
define the law of constancy of interfacial angles
formulated by steno
the angles between corresponding crystal faces have the same value
what does the term ‘texture’ refer to in rocks?
the way in which individual mineral grains are intergrown
What is the most abundant class of rock-forming
minerals?
silicates
what is a phenocryst
large crystals in a matrix of much smaller crystals
what is the most abundant rock type found on the of the earth
basalt
What is the
most abundant type of rock making up the surface of the Earth?
igneous rock
what is the largest rock factory on earth?
divergent Margins
describe the process of a divergent rock factory and the composition of the rock
magma upwells from MOR, spews into ocean, produces pillow basalts. composition ALWAYS basalt
describe the process of a convergent rock factory and the composition of the rock
most rock produced here is subducted back into the mantle. andesite produced
describe the process of a divergent rock factory and the composition of the rock
forms rift valleys
describe the process of a mantle plume- hot spot rock factory and the composition of the rock
Hot spots remain stationary while plates move over hot spot.basalts form above hot spots
describe the process of a passive margin rock factory and the composition of the rock
passive margins form following rift events
what are the important physical properties when determining a mineral?
-color
-luster
-hardness
-specific gravity
-streak
-habit
-aggregation
describe a minerals habit and give some examples:
the external shape of individual crystals
- acicular (needlelike points)
- tabular (layered tablets)
- dendritic (treelike branching)
- massive (devoid of crystal faces)
describe a minerals state of aggregation and give some examples:
The overall form of crystals grown together
- Granular (consisting of grains with equal dimensions)
- oolitic (consisting of rounded masses <2mm in size)
- compact (consisting of grains so fine aggregation cannot be determined with the naked eye)
describe a minerals cleavage and give some examples:
cleavage relates to how the crystal would break along crystallographic angles.
- planar
- prismatic
- cubic
what are trace elements
elements NOT essential to the mineral
what are molecular orbital transitions
results from the TRANSFER of electrons between adjacent cations
what are the three most important atom/atomic sites responsible for color?
- crystal field transitions
- molecular orbital transitions
- color centers
what are crystal field transitions?
the interaction between white light and partially filled D orbitals
what are chromophores and give three examples
color causing elements
- Fe
- Ni
-Zn
what are color centers
ionic vacancies in mineral structures filled with an excess electron
why might trace elements exist
in a minerals where they normally should not be present?
can occur in
lattice sites deformed by flaws or similar ionic radii to the element they are substituting for
what are coordination numbers and what do they represent
describes the number of closest neighbors surrounding a central ion. the CN is a function of the relative sizes of cations/anions
what are the five radius ratio limits, their coordination number and the resulting geometric shapes
- RR=0.155-0.225
CN=3
Triangular coordination - RR=0.225-0.414
CN=4
Tetrahedral coordination - RR= 0.414-0.732
CN=6
Octahedral coordination - RR=0.732-1.0
CN=8
Cubic coordination - RR= 1.0
CN=12
Closest packing
what is the difference between hexagonal and cubic closest packing?
HCP has a packing sequence of ABABAB…
CCP has a packing sequence of ABCABC…
what is the first of Pauling’s rules
coordination principle- CN are determined by the ratio of cation to anion radii
what is the third of Pauling’s rules
sharing of polyhedral elements I- the sharing of edges of faces between Polyhedra is unstable
what is the second of Pauling’s rules
electrostatic valency principle- the strength of a bond is equal to ionic charge divided by coordination number
what is the fourth of Pauling’s rules
sharing of polyhedral elements II- cations of high charge AND small CN do not share polyhedral elements with each other
what is the fifth of Pauling’s rules
principle of parsimony- the number of different types of cations are limited
what is isodesmic structure
all bonds are equal strength
what is a mesodesmic structure?
electro valency number is 1/2 the valence number of the cation
what is a aniodesmic structure?
bonds are different strengths
what are the four types of bonds
- ionic
- covalent
- metallic
- van der waals
hown do ionic bonds work
the exchange of electrons
what are the strongest bonds
ionic
how to covalent bonds work
the sharing of electrons
what are the weakest bonds
van der waals
what does solid solution mean?
minerals can have a range of compositions withing some finite limits
at what percentage is difference complete solid solution?
15%
at what percentage is difference limited solid solution?
15-30%
at what percentage is no solid solution possible?
> 30%
how can ions of different charge but similar size be substituted?
coupled substitution
what is substitutional solid solution?
simple cation and anion substitution
when does interstitial solid solution occur?
when a specific atomic site is normally empty but may host additional ions in the interstices of a structure
what is omission solid solution?
implies unfilled or vacant atomic structures
commonly referred to as DEFECT structures
what is a symmetry element?
features that express the symmetry of an ordered arrangement
what is a symmetry operation?
the process that results in a symmetry element
what are the four symmetry elements?
- mirror plane
- rotation axis
- center of symmetry
- rotoinversion axis
what is a mirror plane
an imaginary line dividing a crystal, in which either side of the line a symmetrical
what is a rotation axis
two imaginary points, located opposite each other through which an object can be rotated around x times and the image is the exact same
EX: a three bladed fan could be rotated three times and produce the exact same image each time (called a threefold rotation axis)
what is a center of symmetry
when a face has another identical, but opposite face
what is a rotoinversion axis
an object has a rotoinversion axis if it can be rotated AND inverted and still remain the same
what are the six crystal systems?
- isometric
- Hexagonal
- Tetragonal
- Orthorhombic
- monoclinic
- triclinic
what are crystallographic axes?
three imaginary reference lines
what is the only crystal system that has four crystallographic axes?
hexagonal
what do symmetry contents notation indicate?
a shorthand way of describing symmetry content
what are miller indicies
the intercepts of the X,Y,Z axis respectively.
why does crystal twinning form?
a rational, synthetic intergrowth of two or more crystals
what are the possible twin elements
- contact twins
- penetration twins
- multiple twins
define contact twins
a composition plane joins the two individuals, separated twin plane
define pentration twins
intergrown crystals
define multiple twins
2 or more crystals repeared by the same law
define polysynthetic twins
occurs if all composition surfaces are parallel
what is a twin plane?
surface along which lattice points are shared
what is pericline twinning?
microcline twinned according to the pericline law
what is polymorphism?
the ability of one chemical compound to occur in more than one type of structure as temperature/pressure changes
EX: Carbon produces diamond AND graphite
what is polytyptism?
a kind of polymorphism in which
what is order displacive polymorphism?
when a solid solution of two elements occur at a specific site
