atoms and minerals
calcite (calcium carbonate), quartz, feldspars, muscovite and biotite mica, amphiboles (hornblende), pyroxenes (augite), olivine
- the eight most abundant chemical elements in the crust
- protons, neutrons, electrons and how they compose atoms
- the difference between atoms, elements, ions (cations), compounds, minerals, and rocks
- definition of an element
- definition of a mineral
- chemical bonding: covalent and ionic
- the mineral classes
- silicates, silica, silicon
- silicate mineral structures and properties
relative ionic vs. covalent bond character
relative silica content
metal cation content (esp. Fe & Mg)
felsic vs. mafic
- mineral properties (crystal form, cleavage type, hardness, etc.)
determined by orderly arrangement of atoms and bond strength
igneous bodies: volcanoes and plutons
igneous activity and plate tectonics
convergent plate boundary subduction zones:
volcanic arcs (e.g., Andes)
island arcs (e.g., Aleutians)
divergent plate boundaries:
midocean ridges (e.g., Mid Atlantic Ridge)
continental rifts (e.g., East African Rift)
intraplate volcanoes - hotspots
e.g., Hawaii
volcano size due to volume of erupted lava
volcano shape due to lava viscosity (resistance to flow)
mafic lava, hi temp, low viscosity, gently sloping volcanoes
intermediate to felsic lava, lower temp, higherr viscosity, steeply sloping volcanoes
shield volcanoes (e.g., Hawaii): mafic lava
fissure eruptions: basalt plateaus, flood basalts (e.g., Columbia flood basalts)
cinder cones: small volcanoes formed from pyroclastic eruptions (granular materials lie at the angle of repose)
pyroclastic particle sizes: bombs, lapilli, ash
stratovolcanoes (e.g., Fuji, St. Helens, Vesuvius): alternation of andesite flows and pyroclastics
caldera eruptions (e.g., Mt Mazama-Crater Lake, Krakatao): massive eruptions that violently empty magma chamber
overlying rock sinks down into void leaving caldera where volcano once stood
volcanic neck
lava flow textures: pahoehoe, aa, columnar joints
igneous intrusions
massive: stocks, batholiths, laccoliths
tabular: dikes, sills
sedimentary rocks
conglomerate, sandstone, shale, limestone, coal
the 5 steps in the formation of sedimentary rocks
1. weathering of pre-existing rocks produces sediments
2. transport
3. deposition
4. compaction
5. cementation (4 & 5 result in lithification)
1. weathering
mechanica:
stream abrasion, sand blasting, frost wedging, root wedging, fires (thermal expansion)
chemical:
Goldich Stability Series (vs. Bowens R.S., and silicate structures)
dissolution (e.g., ionic compounds like halite in dipolar water)
formation of carbonic acid:most natural surface waters slightly acidic
hydrolysis: silicate minerals in acid solution alter to clays + soluble ions
oxidation: esp. of iron ions to form insoluble iron oxides (e.g., hematitie) and hydroxides
weathering products: gravel sand, silt, clay, ions
2. transport: via streams, wind, glaciers, waves
bed, suspended, and dissolved stream loads
Hjulstrom diagram: stream velocity required to erode and transport seds of various sizes
sorting and rounding
3. deposition (e.g., when stream velocity drops)
sediments are deposited in horizontal layers (cross-bedding not withstanding)
oldest layers are on the bottom, younger toward the top
4. compaction
not much in coarse sediments
especially important for clay-rich muds - they align flat like sheets of paper
5. cementation:
crusts of minerals precipitated from ions dissolved in water in voids between sedimentary particles
common cements: silica, calcite (fizzes), hematite (red)
classification of sedimentary rocks
clastic: conglomerate, breccia, sandstone, shale
biogenic (biochemical): limestone, dolomite, coal
chemical precipitates: halite, gypsum, limestone (incl. oolitiic limestone)
the importance of sedimentary rocks
fossil evidence for past life
record of past geography: marine vs. terrestrial, stream deposits, desert deposits
record of past environments: black organic rich seds vs. red well-oxygenated seds
energy: coal, source of petroleum and natural gas
metamorphic rocks
slate, schist, gneiss, quartzite, marble
conditions for metamorphism
pressure and heat (not so much to melt the rocks)
fluids (water and carbon dioxide stored in rocks)
commonly caused by deep burial associated with tectonic collisions and mountain building
some minerals are stable at low temp/pressure conditions while others are stable at various depths (pressures/temperatures)
retrograde (reverse) metamorphism very slow because it occurs more slowly than the peak metamorphism (b/c lower temp)
protolith --> meta rx (characteristics of meta rx compared to their protolith)
examples:
foliated (w/ slaty cleavage, schistosity, gneissic banding)
shale --> slate (characteristics of each)
bedding plane cleavage, relict bedding
shale --> schist
granite --> gneiss
non-foliated
sandstone --> quartzite
limeston --> marble
the concept and interpretation of metamorphic index minerals (guide to meta intensity/burial depth)
structural geology
joints, faults, folds, metamorphic foliation
- compression, tension, shearing stress
- initial elastic response to stress
- brittle vs. ductile response to stress
- joint sets
- the 3 categories (4 types) of faults and the stress environments in which they are found
- hanging wall and footwall blocks
normal faults (extension)
crustal thinning and lengthening
horst & graben (Basin & Range Province)
half-grabens (Newark Basin & East African Rift)
thrust & reverse faults (compression)
crustal thickening and shortening
mountain belts, collisions (e.g., modern Himalayas, ancient Appalachians)
strike-slip faults (shearing)
San Andreas Fault, North Anatolian Fault (Turkey)
- folds
anticlines and synclines and age relations from core to limbs
fold axis and axial plane, limbs
plunging folds
domes and basins
valley and ridge topography resulting from differential weathering of folded strata
- foliation
axial planar cleavage
- orientation (strike) of faults, folds, and foliation relative to the applied (tectonic) forces
earthquakes
- strain buildup -> rupture (slippage) on faults -> seismic waves propagate outward through Earth
- body waves: P waves, S waves
- surface waves: Love waves, Rayleigh waves
- epicenter and focus (hypocenter)
- basic principal of seismometers
- determing distance from earthquake by S-P interval
- earthquake location via triangulation (S-P interval from three seismic stations)
- information needed to determine an earthquake's magnitude (
S-P interval (to determine distance)
wave amplitude at recording station
- the Richter magnitude scale of earthquake strength: logarithmic scale (powers of 10)
- earthquake prediction: only on a statistical basis
- local bedrock geology and earthquake damage risk
Midterm Exam