ESC1000 Midterm
ions
an atom or molecule with a net electric charge due to the loss or gain of one or more electrons
compressional differential stress
shortens a rock body
element
a substance that cannot be broken down by chemical means
rock strength
amount of stress a material can endure before it strains
mole
6.02 x 10^23
synthetic diamonds
>80% of diamonds produced are synthetic
rock types reveal
info about past environments, especially when compared to modern systems
you can find larger river systems near
larger mountain belts
mud (clastic sedimentary)
mudstone & shale
anions
negatively charged ions
atmosphere contains mostly elements
nitrogen & oxygen
unloading
occurs when overlying material, such as soil or another rock stratum, is removed (most commonly through erosion) and confining pressure on the underlying rock is decreased. In response, the rock generally fractures into sheets which lie perpendicular to the direction in which pressure is released.
cementation
precipitation of dissolved ions in pore space "gluing" minerals
mud cracks
preserved in rock tell us that the area was very wet at certain times ex: floodplain or tidal flat
Blue diamonds
Diamond, B
Schrodinger model
Quantum mechanics
cations
positively charged ions
color of diamond
-colorless: no impurity, pure Carbon -yellow: Nitrogen -blue: Boron
internal structure of minerals
"How it's put together" -As a function of bond type & strength, structure affects hardness -Geometry of structure affects mineral form
composition of minerals
"What's in it" this can affect color and bond strength
atomic #
# of protons
strain in deformation
-"changes" in the shape due to stress -"results" -rocks exhibit strain brought by the forces of stress ex: faulting, folding, & flowing
brittle deformation (fracture)
-after stress is removed, rock does not return to its original shape -permanent & irreversible -loses structural continuation
ductile deformation
-after stress is removed, the rock does not return to its original shape -permanent & irreversible -plastic deformation -structural continuation inside
elastic deformation
-after stress is removed, the rock returns to its original shape -nonpermanent, reversible
magma intrusion
-alters the local geothermal gradient -raising temperature -metamorphoses adjacent rock
gems prized for
-beauty (color, transparency, durability) -durability (hardness, resistance to abrasion)
fossils
-biologic remains in sedimentary rock -used to interpret ancient environments from their buried remains -ions in pore water may replace original cellular matter, usually quartz, calcite, or hematite
low-grade metamorphism
-burial to 12km -temp about 240 C
buying a diamond (C's)
-carat -color -clarity -cut -cost
partial melting
-causes wide variation in chemical composition -each mineral has different melting temperature -each element has different tendency to move into melt
clastic sediment
-composed mainly of mineral grains weathered from pre-existing rock & cemented together by precipitated minerals -texture
marble
-composed of calcite -white -from limestone
chemical/biogenic sediment
-composed of minerals precipitated from water by biologic or inorganic processes, or the remains of organisms -composition
mafic rock
-dark-colored igneous rock containing minerals such as pyroxenrs & olivinez that are rich in iron & magnesium while relatively poor in silica -form in the seafloor MAgnesium-FerrIC
sedimentation
-deposition of sediments -after being carried away by water, wind, or ice, sediments are deposited -typically in formations called beds or layers -usually horizontal
Thomson & Rutherford
-discovered electron (1897) -plum-pudding model (1904) -discovery of nucleus from scattering experiment (1911) -nature of nucleus --> field of nuclear physics
Bohr model
-discrete energy levels in electronic structure -shell model (1913)
temperature in metamorphism
-drives away water & gases -enhance diffusion of elements/ions -induces chemical reactions -different minerals are stable in different physical conditions (ex: water, ice, vapor vs diamond & graphite)
effusive volcanism
-erupted lava typically liquid -dissolved gas comes out quickly as pressure decreases -low viscosity
rhyolite
-felsic -igneous -extrusive
granite
-felsic -igneous -intrusive
bioturbation structure
-footprint of animals on bedding surface -can tell us which side is up
sedimentary rocks
-formed by deposition and precipitation of materials coming from the breakdown of older rocks -soft (less resistant to erosion) -weathering breaks down & dissolves parts of a rock (clastic sediment / dissolved ions)
sand (clastic sedimentary)
-grain size: 1/12-2mm rock name: sandstone -quartz sandstone (95% quartz grains) -Arkose (25% feldspar w/ quartz) -lithic (90% quartz & more rock fragments than feldspar)
gravel (clastic sedimentary)
-grain size: larger than 2mm -rock name: -breccia (if fragments are angular) -conglomerate (if if fragments are rounded)
physical properties of diamonds
-hardest natural substance -high dispersion (white light into rainbow colors) -high luster
gneiss
-high metamorphic -from schist or granite -foliated
foliation
-how rock texture record strain -role of pressure in metamorphism
four sources of natural diamonds
-impact sites (very rare, nanodiamonds) -meteorites (very rare, nanodiamonds) -deeply-buried crust @ low geothermal gradients (rare, microdiamonds) -mantle-derived kimberlites (abundant, most jewelry or industrial diamonds)
how to melt a rock
-increase temperature -lower confining pressure -add water
schist
-intermediate metamorphic -from phyllite -foliated
phyllite
-intermediate metamorphic -from slate -foliated
diamond uses
-jewelry -abrasives, drill bits, saw, semiconductors -high pressure apparatus
crystallization
-key process in mineral formation -process of formation of solid crystals from a uniform solution -minerals grow outward from a central seed to fill the available space; their shape is controlled by the shape of their surroundings
batholith
-largest kind of intrusive igneous body -major batholith in the West Coast -felsic or intermediate rock types
felsic rock
-light-colored igneous rock that is poor in iron and magnesium while rich in high-silica minerals (quartz, orthoclase feldspar, & plagioclase feldspar) -form in continental plates FELdspar-SIliCa
slate
-low metamorphic -from shale or mudstone -foliated
Magma formation processes in Earth
-lowering confining pressure (decompression melting: Mid-Ocean Ridge) -adding water (Hydration melting: Subduction zone) -Increasing temperature (Temperature-Induced Melting)
basalt
-mafic -igneous -extrusive -from volcanoes
gabbro
-mafic -igneous -intrusive
stress deformation
-magnitude of force per unit area -"cause"
oceanic crust
-mainly composed of basalt -phynocryst: A few visible large crystals which crystallized in magma and brought onto surface with magma
factors controlling weathering rates
-mineralogy -rock type & structure -slope angle -climate -presence/absence of soil -time -water -temperature
Mineral
-naturally occurring -inorganic solid -ordered internal molecular structure -definite chemical composition ex: quartz, biotite, plagioclase
diamonds
-nearly pure elemental carbon -high pressure form
Weathering & Sedimentation
-occurs at sea level around subduction zone
Metamorphism
-occurs in lithosphere of subduction zone
fossil fuels
-organic matter buried w/ sediment changes under increased temperature over time to combustible organic compounds such as coal, oil, & natural gas -stored chemical energy from the sun -energy can be released by oxidation (burning)
main components of metamorphism
-original rock material -temperature -pressure -fluid (abundance & composition) ---> by burial, intrusion, structural mvts, etc
elements
-over 116 known, 92 naturally occur -defined by # of protons
sediments
-particles of rocks, minerals, or organic matter that are transported by water, wind, or ice ex: sand, mud, silt
chemical weathering
-reaction of rocks w/ water or atmosphere -easily dissolved minerals (ex: halite & calcite) react the fastest -leads to retention of very stable minerals (like quartz) and rounding of mineral grains
quartize
-recrystallization of pure quartz sandstone by metamorphosis -light colored -medium to coarse grained -sometimes foliated
igneous rocks
-rock formed by the solidification of magma -hard (more resistant to erosion)
Rock
-solid aggregate of minerals (+/- non-minerals such as volcanic glass or organic matter) ex: basalt, granite, limestone
limestone
-sources of calcite: marine organism (shell + skeleton) & dissolved CaCO3 -forms in warm area in shallow ocean -10% by volume of total sedimentary rocks -very important sink of atm CO2 -soluble -generate landforms w/ pavements, sinkholes, caves -popular in architecture (heavy & $$$)
uniform stress
-stress equal in all directions -changes volume, but not shape ex: burial
differential stress
-stress strongest in one direction -changes shape -more common
measure of strain
1. length change 2. volume change
factors that influence deformation
-temperature -confining pressure -rock type (composition) -rate of deformation
depositional environments
-the characteristics used to name sedimentary rocks also can be used to interpret the history of an area ex: sea floors, beaches, stream beds, swamps (all have diff. sedimentary characteristics)
magmatism
-the motion or activity of magma -occurs at Mid-Ocean Ridge, Volcanic Arc, & Hot Spots
lava flow distance
-viscosity (low -> extended flow) -melting temp (low -> extended flow) -eruption rate (high -> extended flow)
how does magma form?
1. Lower confining pressure 2. Add water 3. Increase temperature
role of fluid in metamorphism
1. react w/ minerals to form new minerals that contain components of the fluid molecules -OR- 2. change the metamorphic rock by delivering & removing dissolved ions, fluid makes reactions occur faster & more easily
as grains travel from the source
1. roundness increases 2. size decreases 3. sorting increases
cleavage
1. the tendency of a crystal to break along planar surfaces 2. the geometric pattern produced by such breakage
lava tube
A natural conduit through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like channel
Emeralds
Beryl, Cr
Aquamarines
Beryl, Fe
Sapphires
Corundum, all colors besides red
Rubies
Corundum, red color, Cr
metamorphism
Describes the mineralogical, chemical, and textural changes to preexisting rocks that occur in a (more or less) solid state due to increased temperature & pressure
Yellow diamonds
Diamond, N
relatively high abundance of elements
Fe, Ni, Pb
biological activity
Growing plant roots can exert stress or pressure on rock. Although the process is physical, the pressure is exerted by a biological process
wet/hydration melting
H20 in the form of steam dissolving into rock which causes the rock to melt at a lower temperature
most abundant elements
Hydrogen & Helium (more than 99% of all atoms)
relatively low abundance of elements
Li, Be, B, Sc
hardness scale
Mohs Scale of Hardness 10 Diamond 9 Corundum 8 Topaz 7 Quartz most gems are 7 or higher
covalent chemical bond
atoms share outer electrons
most abundant mineral in Earth's crust
Silicate (Si-O chain)
hardness
a measure of the ease with which the surface of a mineral can be scratched
gemstone
a mineral, rock, or petrified material that when cut or faceted and polished is collectible or can be used in jewelry
frost wedging
a physical weathering process in which the expansion of freezing water in cracks in rock breaks the rock
color & streak
a property of a mineral imparted by transmitter or reflected light
explosive volcanism
a volcanic term to describe a violent, explosive type of eruption
intermediate igneous rock
an igneous rock midway in composition between mafic and felsic, neither as rich in silica as felsic rock nor as poor in it as mafic rock
dunes & ripples
are both formed by the direction of forces (winds & currents) to which they are subjected
crystal growth
as water percolates through fractures and pore spaces it may contain ions that precipitate to form crystals. As these crystals grow they may exert an outward force that can expand or weaken rocks
isotopes
atoms of the same element with different numbers of neutrons
most abundant extrusive rock
basalt (mafic)
classification of igneous rock
based on: -texture (ex: grain size) -chemical composition (ex: SiO2 content)
colors in gemstones/minerals
caused by: -defects in crystal structure -intrinsic chemical constituents -chemical impurities
shear differential stress
causes rocks to slide past each other
deformation
changes in location, orientation, shape, &/or size of a rock body
seawater is full of elements of
chloride & sodium
pyroclastic flow
cloud of debris is very fast, very hot, & contains huge blocks (most devastating)
intrusive igneous rock
coarse-grained igneous rock formed from magma that intrudes into country rock deep in Earth's crust and cools slowly (large crystals)
chemical sedimentary rocks
comp: --- rock name: calcite --- limestone dolomite --- dolostone quartz --- chert
tectonic uplift rate
controls erosion rate & vice versa
lithification
conversion of sediments into rock via compaction & cementation
compaction
decrease in volume due to loss of pore space
metallic chemical bond
electrons move from atom to atom, inner electrons shared
Van der Waals chemical bond
electrostatic forces causing dipole movement (microscopic separation of positive and negative charge centers)
tensional differential stress
elongates a rock body
atomic mass
equal to average number of protons plus neutrons
Karst
erosion landscaping made of limestone
extrusive igneous rock
fine-grained or glassy igneous rock formed from magma that erupts at Earth's surface as lava cools rapidly (tiny crystals)
most abundant intrusive rock
granite (felsic)
Isostasy
gravitational equilibrium between lithosphere (rigid material) and asthenosphere (fluid)
Z elements
greater abundance of even Z elements compared to odd Z elements
clarity
how clear a diamond is (free from inclusions and blemishes) - FL-flawless - IF-internally flawless - VVS1 and VVS2-very very slightly included - VS1 and VS2-very slightly included - SI1 and SI2-slightly included - I-imperfect (visible with naked eye)
continental crust
mixture of intrusive and extrusive igneous rocks (+ metamorphic and sedimentary rocks)
polymorphs
one of 2+ alternative possible crystal structures for a single chemical compound ex: the minerals quartz and cristobalite are polymorphs of silica
ionic chemical bond
oppositely charged ions attract
important minerals
ore minerals & gems
most minerals made of the elements
oxygen & silicon
fossils used to interpret
past environments (climate & vegetation)
physical weathering
processes that break rock into smaller fragments
chemical weathering
processes that dissolve some minerals (causing dissolved ions to be carried away) and to create new minerals
recrystallization of minerals into new sizes & shapes
sandstone (sedimentary rock) -> quartize (metamorphic rock) limestone (sedimentary rock) -> marble (metamorphic rock)
dike
sheet of rock that formed in a crack in a pre-existing rock body
compound
substance formed by two or more elements chemically bonded together
thermal expansion
sudden exposure to high temperature may cause expansion and eventual breakage of rock ex: wildfire
minerals used "as found"
sulfur, silver, gold, diamond
sill
tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock.
geothermal gradient
temperature increases w/ depth into Earth
atom
the basic unit of a chemical element, smallest particle that retains distinctive properties of an element
density
the mass per unit volume of a substance ex: g/cm^3
weathering
the physical or chemical breakdown of rocks at Earth's surface
erosion
the physical removal of material by water, wind, ice, or gravity (transport)
crystal form & growth habit
the shape in which a mineral's individual crystals or aggregates of crystals grow
decompression melting
the spontaneous melting of rising mantle material as it reaches a level where pressure decreases below a critical point, without the introduction of any additional heat
luster
the way the surface of a mineral reflects light
streak
thin layer of powdered mineral made by rubbing the specimen on the place
how do we determine mineral stability?
using a cylindrical pressure chamber
kimberlites
volcanic pipe, explosive volcanic eruptions from deep in the earth that bring already formed diamonds to surface
rock cycle
weathering-erosion-deposition-lithification-metamorphism-melting-crystalization-uplift-weathering
reverse faulting
when one block of crust is forced over another, the lower one heats to a temperature associated with its depth
thin section
when you cut and glue rocks and minerals on a glass slide and sand it
approximate # of known minerals
~4,000